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1. AMPEX
   Ampex Electric Corp., 1151 Howard Avenue, San Carlos, California
2. AUDIOGRAPH
   Audiograph Co., 1434 El Camino Real. San Carlos, California
3. RE-CORDO-FONE
   Bell Sound Systems, Inc., 1183 Essex Avenue, Columbus 3, Ohio
4. SOUNDMIRROR
   Brush Development Co., 3405 Perkins Avenue, Cleveland 14, Ohio
5. EICOR
   Eicor, Inc.. 1900 W. Congress, Chicago 7. Illinois
6. FAIRCHILD
   Fairchild Recording Equipment Corp.. 154th St tf 7th Ave., Whitestone. N. Y.
7. LEKAS
   Lekas Mfg. Co., Ann Arbor. Michigan
8. MAGNECORDER
   Magnecord, Inc.. 160 N. Michigan Avenue. Chicago 1. Illinois
9. MASCO
   Mark Simpson Manufacturing Co.. Inc., 32-28 49th St., L.1!. C. 3. NY
10. PELCO
    Pelco Industries, 629 Second Avenue. New York, N Y
11. PRESTO
    Presto Recording Corp.. P.O. Box 500. Hackensack. N.J.
12. RCA
    Radio Corp. of America. RCA Victor Div , Front Cooper Str.. Camden 2, N.J.
13. RANGERTONE
    Rangertone, Inc., 73 Winthrop Street. Newark 4. N. J.
14. REVERE
    Revere Camera Corp. 320 E. 21st St., Chicago 16.
15. Rack Mounted Recorder, PORTATAPE & MINITAPE
    Stancil-Hoffman Corp . 1016 N Highland Ave , Hollywood 38, Calif.
16. TAPETONE
    Tapetone Maufactunng Corp., 1650 Broadway. New York 19. N. Y.
17. EKOTAPE
    Webster Electric Co., Racine, Wisconsin
18. RECORDIO
    Wilcox-Gay Corp.. Charlotte Michigan
19. TWINTRAX
    Amplifier Corp. of America. 398 Broadway, New York 13, NY.
20. ULTRATONE
    Audio Industries. Michigan City. Indiana
21. MAGICTAPE
    Crestwood Recorder Corp., 218 S. Wabash. Chicago 4. III.
22. DuKANE
    Operadio Manufacturing Co.. St. Charles, III.
23. ASTRASON1C
    Pentron Corp.. 611 W. Division Street. Chicago 10, Ill.

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An Example of Cooperation in Inter-denominational Recording and Broadcasting
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• Anmerkung : Dieser Artikel zeigt auf, daß die religiösen Sender und Sendungen in den USA bereits 1950 einen sehr hohen Stellenwert hatten.

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There recently opened in Decatur, Georgia, a part of greater Atlanta, a unique radio and audio visual production center which is attracting national notice. It is known as the Protestant Radio Center. It is not a radio station, but it has the finest equipped studios for broadcasting, recording, and producing programs for radio and for audio visual aids. It is unique in that it is the only inter-denominationally owned and controlled institution of its kind in America.

The Center is a venture in Protestant cooperation, and the one word which sums up its purpose is just that - cooperation. Cooperation among the denominations.

Four years ago four denominations interested in producing religious radio programs formed the Southern Religious Radio Conference. They have produced one or more programs every week ever since January 1, 1946.

Cooperation with the radio stations. The Conference started with 26 stations which accepted the programs on a sustaining basis. There are 97 stations now affiliated with the Conference. This is one of the biggest networks for a sustained religious radio program in the nation today. The stations at present extend from Washington, D. C. to Amarillo, Texas and Gallup, N.M.; from Kearney, Nebraska to Miami, Florida. Most of the fifty thousand watt stations in this territory accept these programs.

Cooperation in production. These denominations, with this large number of stations, felt the need of a production center, jointly owned and controlled by the members. Consequently an application for a non-profit charter was drawn up and filed by the late Allen W. Clapp, one of the outstanding Atlanta attorneys. The charter was granted by the state of Georgia, and the corporation has been
recognized by the Federal Government as a tax-exempt corporation, gifts to which may be deducted in estimating federal income tax.

The basis of the corporation was extended to church affiliated educational institutions and interchurch agencies. The charter authorizes radio production, recording, audio-visual aids, laboratory research and teaching.
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The founders of the corporation were Emory University, Candler School of Theology, Agnes Scott College, Columbia Theological Seminary, the Southeastern Inter-Council Office, and the radio committees of the Methodists, Presbyterians, Episcopalians and Lutherans (United). Aided by an anonymous grant, the Center starts off with assets of $ 25.000 cash and equipment.

The Center is installed in the music building of Agnes Scott College, one of the finest of its kind in the land. The equipment is of the latest model. The Center has a portable tape recording unit for remote use. It is equipped to cut recordings for radio use; 16" at 33 1/3 rpm. It can also cut phonograph recordings at the conventional 78 rpm and also the long playing microgroove type.

Cooperation on the national level. The Protestant Radio Center is the official regional outlet for the programs of the newly organized national Protestant Radio Commission of New York. In addition to that the Center produces programs for the nation-wide networks. This fall it produced a program for the Mutual net. A program for the Columbia Church of the Air originated here. For four months during the summer of 1950 the NBC National Radio Pulpit will originate at the Center.

Dean H. B. Trimble of the Candler School of Theology is the President. Dr. John M. Alexander, secretary of the Radio Division of the Presbyterian Church US, is the Executive Vice President. Dr. John R. Brokhoff, pastor of the United Lutheran Church of the Redeemer, is secretary, and Mr. George H. Mew, of Emory University, is the Treasurer. Mr. Warde Adams, Jr., is the Production Manager, and Mr. M. F. Adams, Jr., is consulting engineer.

By Llewelyn Lieber - Director of Audio-Visual Education

"Oh, how I wish my students could have heard that!" is no longer a familiar cry in the St. Louis public schools. For now tape and disc recordings bring treasured auditory experiences right into the classroom. The Division of Audio-Visual Education maintains a recordings library which incorporates all the regular uses of recordings and a few which may be unique. For instance, at an Open House two exchange students from Bangkok were guests. They were escorted into a room and a recorder took down their impressions of education in the United States and their answers to questions concerning the Siamese system. And when the Freedom Train visited St. Louis, it called forth the presentation of two radio programs on the Revolutionary Era. The Division of Audio- Visual Education made recordings of these broadcasts so that they might be used for future history classes; for demonstrations on recorder techniques; and for the personal benefit of the participating students.

The in-service teacher training program has benefited from the synchronizing of Kodachrome slides with magnetic recordings. This device has been used to show student-teachers how a St. Louis teacher in a special education, developed a Christmas program - how deaf children are taught in Gallaudet School. These soundpicture projects have been used in talks to parent groups, members of the Board of Education, and to other civic groups.

Radio programs originating from the Division of Audio-Visual Education have profited from the use of tape and disc recordings, for it is a most effective way to develop new series. For example, Dr. John Whitney, Consultant in Science at Harris Teachers College, inaugurated a new series of programs designed to guide elementary children with scientific experiments in the classroom. Before going on the air, tape recordings were made and taken into classrooms where the teachers and pupils listened critically for flaws in technique.

These were corrected and a new recording tried out on other groups until pace, content, and voice quality were satisfactory. Finally, a disc was made and tried out with a regular elementary classroom on their school stage following the recorded directions while an audience of teachers and principals observed the entire procedure from the auditorium. Acceptance was unanimous so the series was put on the air.

All radio programs sponsored by the Division of Audio- Visual Education are recorded on discs, and these are auditioned by a committee of ten St. Louis Public School teachers, who make a written evaluation of each program. At the conclusion of the series a tally of the recommendations is made and if the teachers believe the programs merit inclusion in the recording library, dubs are made and placed in service for issue to the schools whenever teachers request them.

To celebrate "Writer's Day," Blewett High School invited Miss Clarisa Start, feature writer for the St. Louis Post-Dispatch, Robert Hereford, author of "Old Man River" and feature writer for the Globe-Democrat, and Mrs. Fannie Cook, author of "Mrs. Palmer's Honey" and other novels, to speak to the student body. The speakers told the techniques employed when writing for a newspaper and when writing a book. Now future English classes can benefit from these authorities for the Division of Audio- Visual Education made a recording of the entire program.

When eighth grade pupils of Cupples School visited Missouri's capital in Jefferson City, the Division of Audio- Visual Education made a recording of their impressions of the trip after they returned. Seventh grade pupils of the same school interrogated the children who had made the excursion and this resulted in a clarification of benefits derived from the trip, a review of facts learned and a permanent record for future reference.

Celebrities visiting the Division of Audio-Visual Education are usually interviewed with a recorder so that a library of talks by outstanding authorities on various subjects is gradually being assembled. This is available for use in public relations work, teacher training, workshop courses and special subject classes, and will be valuable to posterity as a means of hearing famous people express themselves.

The Division of Audio- Visual Education follows the routine procedure of using recorders for perfecting speeches to be made by staff members; for correcting errors in children's classwork in English, dramatics and reading; and for recording radio programs for school use which come over the air after school hours or at inconvenient times during school hours. Yes, the schools have really "gone on record" here in St. Louis.

by C. J. LeBel, Vice President, - Audio Devices, Inc.

With the advent of magnetic recording, many engineers have suddenly developed a new interest in magnetic fundamentals, a subject carefully forgotten since college days. To appease them we will proceed to discuss some basic magnetics, using industry practice in terminology rather than the official AIEE standard. Finally, we will give magnetic data on both red and black AUDIOTAPE.

In Fig. 1 we show a typical relation between the magnetizing force applied to a material and the resulting magnetic induction (magnetization). This curve show's, what happens when you start with a completely de-magnetized material, and increase the magnetizing force progressively.

Note that the curve levels off at the upper end as saturation is approached (point A). If we now Aeciease the magnetizing force from its peak value A back down to zero, the magnetic induction will fail to retrace the curve previously followed. Instead, it will decrease much more slowly, following the dotted line AB shown in Fig. 2. Even when the magnetizing force has dropped to zero, a certain amount of residual magnetization remains (point B).
 
To remove this, it is necessary to apply a magnetizing force of opposite polarity. The curve will then be as shown by the dotted line BC in Fig. 2. Then, if this negative magnetizing force is progressively increased, the curve will continue along dotted line CD, approaching negative saturation and returning along dotted line DEFA as the magnetizing force is reduced to zero and then increased positively again.

This failure of the curve to retrace its original path is called hysteresis, and the dotted curve shown in Fig. 2 is a hysteresis loop, the magnetization curve which results when we increase and decrease the magnetizing force cyclically.

Actually, we have oversimplified the matter in Fig. 2, because we do not ordinarily get back exactly to the starting point (A) the first time around the loop. After thirty or forty cyclic variations the loop retraces itself exactly, and it is this which is ordinarily shown, rather than the first loop traced after the initial magnetization curve (line OA).

In Fig. 3, we show typical hysteresis loops for plastic and paper base AUDIO-TAPE. In these illustrations we have, for the first time, introduced units. Magnetizing or magnetic force (usual symbol H) is measured in oersteds, one oersted being the value which would produce a magnetic induction of one flux line per square centimeter in air. Magnetic induction is measured here in maxwells (usual symbol B), the maxwell being a unit indicating the total induction. Another unit of magnetic induction is the gauss, a measure of flux density. One gauss is equivalent to one maxwell per square centimeter.

A great deal of magnetic testing equipment is calibrated in gausses, because it was originally built for testing wire. Since a curve tracer fundamentally reads total induction, the gauss scale is produced by assuming an area of 160 circular mils, a standard wire area. On tape the total coating cross-section will vary, but the customer really buys and uses the total induction, so all of our test data are given in maxwells.

It is easier to classify materials if their characteristics can be summarized in a few numbers, rather than by the infinite number of values given by curves. In the case of magnetic oxides it has become customary to use two index values : the retentivity and the coercive force.

Retentivity is the magnetic induction at which the magnetizing force is zero, in a symmetrical cyclically varying magnetic field. (Laut Wörterbuch ist das aber die Aufnahmefähigkeit bzw. Speicherfähigkeit von magnetischer Induktion) It is marked Br in Fig. 3. The other number is coercive force, which is the magnetizing force at which the rrwgnetic induction 15 reduced to zero in a cyclically
varying magnetic field. It is marked He in Fig. 3. Coercive force and retentivity well define the characteristics of most magnetic materials at 60 cycles, but they are somewhat indefinite as a guide to recording properties, as will be discussed later. As a matter of actual practice, the retentivity is generally determined by application of a 60 cycle field with a peak value of 1,000 oersteds, which is well beyond saturation.

Paper base AUDIOTAPE will have the same coercive force. Retentivity will normally be in the same range, but it is subject to variation over a rather wider range due to variation in paper thickness.

A number of writers have expounded the theory that the high frequency response of a magnetic recording medium correlates directly with its coercive force. This may be termed a cornerstone of the classical theory. Unfortunately, the classical theory is badly oversimplified, and the gap between theory and practice is too wide to be overlooked. The correlation between coercive force and high frequency response exists only when comparing successive batches of nominally identical oxides. It is a fairly satisfactory production control tool, but very dangerous if applied to research results. For example, in comparing a red with a black oxide, it becomes entirely valueless.

Classical theory also indicates that retentivity correlates directly with low frequency response. Again, this is a very oversimplified picture, for the relation works well as a production tool on nominally identical oxides, but fails hopelessly when comparing hundreds of oxides in research. The error may then be as much as 20 or 30db.

It is possible to derive another magnetic characteristic by producing a series of hysteresis loops with diff^erent values for Hm, the maximum magnetizing force. We get a series of values for He and Br corresponding to various values of Hm. The more useful relation is the one between Hm and Br, which we have shown in Fig. 4.

A useful index point which can be derived from this curve is the saturation magnetic force, which is marked on Fig. 4. This is of interest because a tape has to be saturated, at least momentarily, to erase it. The higher the saturation force, the harder to erase. For the particular oxides shown in Fig. 4, the values are 810 oersteds for the black and 710 oersteds for the red.

Seeing that magnetic characteristics are so far from linear, we can only marvel at the effect of AC bias in linearizing the transfer characteristics.

• Anmerkung : Nach dem mehrfachen Lesen dieses Artikels bin ich mir nicht mehr sicher, ob der amerikanische Autor überhaupt verstanden hatte, was er dort ausführt.

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"It's Your Life" lifts the lid on hitherto taboo subjects, in its continuing battle for better health

Chicago's tape-recorded, award winning documentary radio program, "It's Your Life", has blazed many important trails in the broadcasting field. Noteworthy among these has been the fearless and straightforward manner in which they have tackled the delicate problem of sex education. This subject, which has so long been discussed only in whispers or behind closed doors, was given the full treatment in a unique two-part program which pulled no punches and did not obscure its important message with mincing references to the birds and bees.

• Anmerkung : Auch in Amerika war Sex für heranwachsende Jugendliche immer noch ein prüdes bzw. ein Tabu-Thema - über Jahrhunderte fast bis heute.

The first program featured Chicago children discussing sex education with a prominent physician. Segregated groups of 12 year olds told their problems, described physical changes, and explained their feelings on the subject. And the doctor answered all their questions in an equally frank manner. In recording such a discussion, one may readily appreciate the advantages of using tape - with its easy editing (and easy censoring) qualities.

The second program in the series highlighted the lives of two girls - one who suffered tragic consequences as a result of improper sex education, and another who had the benefit of intelligent guidance. The contrast in the lives of these two girls effectively dramatized the importance of sex knowledge in helping adolescents to adjust themselves normally to the physical and mental changes coincident with "growing up".

These two programs achieved a two-fold purpose. One, to give helpful suggestions to parents and point out the value of intelligent sex education in the lives of their children; and two, to instruct the boys and girls themselves who were listening at their radios.

Produced by Ben Park, who has an outstanding record in the Mid-West as a producer of award winning documentary radio programs, "It's Your Life" is designed to show how better health means better community living. Since its inception little more than a year ago, the program has won five awards for excellence as the "most outstanding program of the year" and gained nation-wide attention in the health education field.

In collecting material for "It's Your Life", interviewer Don Herbert and his tape recorder visit homes, hospitals, nurseries, welfare agencies - wherever in Chicago people live and fight battles for better health. For the first time in radio history, listeners have been taken behind the scenes of such reallife dramas as the delicate blue baby operation performed in a Chicago hospital; the birth of a baby in a Chicago home; the treatment for such ills as alcoholism, mental illness, tuberculosis and venereal disease.

"It's Your Life" is produced for the Chicago Industrial Health Association - a non-profit agency made up of 39 member agencies for the good of Chicagoans - and sponsored by Johnson & Johnson, makers of surgical dressings. All programs are reviewed by a medical advisory board for authenticity before being presented over the air. These programs are broadcast at 3:30 P.M., Sundays, over Station WMAQuestion, the NBC outlet.

Mail-Order Tape Service opens vast new field for use of educational recordings

It all began last spring - at the Spring English Conference held at the University of Minnesota. Here, teachers made a strong plea for a lower cost source of recorded material for classroom use. Particular mention was made of the many radio programs on the air which would be of great educational value if they could he brought into the classroom at times when their message or content would be most appropriate.

Since this Conference left no doubt as to the need for good recorded material - at a price within the range of even the smallest schools - the Minnesota Department of Education decided to do something about it. So, with the help and cooperation of the University of Minnesota and a private business concern, a radically new system of making and distributing recordings has been established. This program, organized on an experimental basis, is now in full swing - offering a unique, low-cost recording service to all of Minnesota's 7000 schools.

Final details of the program were worked out largely by Richard C. Brower, audio-visual-radio director for the Minnesota Department of Education, and Betty T. Girling and other staff members of the University of Minnesota Radio Station KUOM.
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The state education department is building up an extensive library of master tape recordings - covering the complete range of subjects appropriate for classroom use. These recordings are being secured from Station KUOM, from the networks, and through the U.S. Office of Education in Washington, D. C. A catalog of the available recordings, with monthly supplements to keep it up to date, is distributed to all interested schools.

In order to participate, the only investment required by the individual schools is the purchase of suitable tape recorders and reels of recording tape. A teacher desiring any of the listed subjects simply fills out an order form specifying the programs wanted, the type of machine on which they will be reproduced, and the desired recording speed in feet per second. This form is then sent in to the Department of Education, together with the required number of reels of "blank" tape. The desired selections are then recorded from the master tape onto the "blank" reels, which are promptly returned to the teacher.

The recordings thus made can be used by the school as desired - cither played back and then erased, kept on file for future reference, or transcribed onto discs for permanent record. Thus, the actual cost for obtaining these educational recordings is only the required postage and the tape itself. As a result of this program, the world's outstanding authorities are now doing important teaching jobs in the Minnesota schools - via low-cost, high-fidelity tape recordings.

• Anmerkung : Und natürlich kein Wort davon, daß in Minnesota natürlich die 3M Tonbänder der 3M - also der dort ansässigen "Minnesota Mining and Manufacturing" Company verwendet werden und wurden.

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• Anmerkung : Das war der "Conrad" oder "Reichelt" oder "Pollin" oder "ELV" aus Amerika im Jahr 1950 nach dem Motto "Wir haben einfach alles." - Übrigens : in USA war ein "Distributor" ganz einfach nur ein oder der Verkäufer, weiter nichts. Hier bei uns ist ein "Distributor" ein Großhändler oder Importeur - ein Lieferant für den Fachhandel und die Industrie.

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The Radio & Electronic Parts Corp. (REPCO), Cleveland. Ohio, has recently moved to a completely new building which has been specially designed throughout to give better "Service to the Customer."

One of the first things that "Repco" patrons (die Kunden) are impressed with is the large parking lot planned for their convenience - a distinct contrast to the Company's previous quarters in the heavily congested, traffic-choked downtown area.

And, once inside the building, it is evident that this same spaciousness and convenience has been followed through in every detail of planning. The main salesroom (where you can buy anything from an Audiodisc to an Audio-point - and a few million other things) has large, roomy aisles, a variety of selfservice island displays, and 60 feet of counter space.

Repco's sound department is of particular interest. Located on a mezzanine extending the full length of the building, it is based on the idea that the best way to give the customer exactly what he wants is to demonstrate it in actual operation. Here, the prospective purchaser can see and hear practically any conceivable combination of audio and video components. Antennas, tuners, amplifiers, microphones, speakers and recorders can be quickly hooked up as desired and demonstrated on the spot.

The arrangement provides for instantaneous switch-over from one combination to another, giving an accurate comparison of the relative merits of the different components. Take TV antennas for example. There are eight different antenna installations on the roof of the building, and the salesman can show a customer the differences in the various models as a function of the image on the television tube.
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REPCO (Radio and Electronic Parts Corp.) has been a distributor of Audio Devices products for the past ten years. They now handle the full line of Audiotape, Audiodiscs and Audiopoints.

They "speak for themselves" - in these comments on the performance of the free samples we sent out
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• A Radio Station: "Superior in ever)- way to any tape we have used so far."
• A College: "Found your tape a very excellent product, and plan to stock it exclusively. Lower hum level most noticeable improvement."
• A Vocation School: "Of several brands of tape tried 'Audiotape' has the lowest consistent noise level. Response is exceptionally constant for all parts of each reel."
• A Radio Station: "Have tried the plastic tape - find it equal or better than other makes. We are now regularly using it for all tape recording work."
• An Industrial Firm: "Thanks for the sample of plastic base Audiotape. I find that It excels all other makes now on the market in quietness, range, and easy handling. Have disposed of all other makes and am using only Audiotape."
• A High School: "Have tested the samples of Audiotape and we are much pleased with it. For our machines your red oxide paper is as satisfactory as the plastic tape we had been using. Our school system is now using this red oxide paper tape as an economy measure over the other plastic."
• A Church: "Your tape is excellent and we will buy it from now on. Also thanks for the 'Audio Record' with articles on tape recording."
• A University: "After trying samples of your paper tapes, ordered 20 rolls. I believe they are the best buy in paper tapes now available."
• A Radio Station: "It is the best tape on the market to date - less noise and under a microscope it is the cleanest tape I have seen. It is the tape we will use here you can be sure of that."
• A Broadcasting School. "Thank you for the Audiotape samples. They are the best we have tried to date. Same high quality as your Audiodiscs. Will order more locally."
• A College: "The plastic base tape I requested was completely satisfactory. There was a distinct reduction in amplitude modulation of high frequencies over a similar competitive tape."
• A Film and Sound Service: "Received sample tape; our findings show after being put through the 'acid test' that Audiotape is far superior to anything we have used yet and we have pretty well covered the field. Prefer the black oxide for excellent bass frequency response."
• A High School: "Excellent - I use recordings in my English classes and find your tape of unusual fidelity."
• A Radio Station: "Like your plastic tape. It does a much better job than any other tape that we've used. Audiotape gets our bid!"
• A Sound Studio: "It was immediately apparent after initial comparisons that paper Audiotape is of a far superior quality. Have been using it exclusively where a paper base tape was indicated. Reels are not subject to scraping or damaging of tape as often the case with other brands."
• A Radio Station: "Very well satisfied with your tape, particularly the plastic. Have the assurance of our chief engineer that we will be in a position to use your plastic tape exclusively when our tape recording operations get into full swing. Our tests indicate that plastic Audiotape is superior in every way to any other."
• A College: "We are using your plastic base Audiotape exclusively for the original recording of our radio programs. We find that there is practically no loss from dub bing from tape to disc."
• A Radio-Ham: "Have used the plastic base tape with surprisingly excellent results. Recordings made of organ music on Audio-tape were transferred to discs with no discernible loss of fidelity. Your product is what the trade calls 'a fine article', and in the words of one radio-ham friend who sees a good thing, 'I'll buy some of that!' Thanks again."
• A Research Lab: "Have found your recording tape to be the best for my recorder. Very low noise level and very uniform characteristics are its outstanding qualities. The price is also attractive."
• A Radio Station: "We have found that the samples of Audiotape meet all the claims you have made for it. We are using some of your plastic tape, which we purchased on the strength of your name and advertisements alone, and have found this tape superior to any we have ever used at this station."

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To date we have received many hundreds of these cards commenting favorably and enthusiastically on the performance of Audiotape. The remarks quoted above are typical. We wish to thank all of these users for the overwhelming vote of confidence.
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by C. J. LeBel, Vice President, - Audio Devices, Inc.

Tapemachine noise is a highly variable factor - it seems to increase under these many changes in condition: from the factory test floor to the recording room, during recording room use, and from one make of machine to another. Since these increases range from 5 to be ignored.

Some increases reflect changing amounts of hum, but much results from an increase in tape hiss. We propose to examine the reasons why a given tape may be so much quieter on one machine than on another; or so much quieter in one recording room than in another, on the same type machine.

Most of the increases referred to result from a change in the character of the effective bias on the tape. Particularly, we believe that they reflect an increase of modulation noise' caused by a dc component of bias flux; or by its equivalent, assymetrical distortion of the bias flux. An actual dc component can origmate in dc leakage through one of the head coils, or in permanent magnetization of the core of a head; assymetrical distortion arises in the bias oscillator or its amplifier, particularly when not push pull.

In order to determine the effect of dc leakage, we set up the circuit of figure 1. An adjustable amount of dc could be passed through the recording head simultaneously with any desired value of bias, and the currents could be measured separately.

The bias used was 5mA at 74 kc, which was a representative bias for this type of head. - The tape used was our red oxide on plastic base. Results are shown in figure 2.

If we study this figure, we note, that noise increases 5db with the passage of only .2 milliampere, which with a 3OO volt dc supply would correspond to a leakage resistance of 1,5 megohms. Since a number of home units have used a blocking condenser, whose insulation resistance could easily fall to 1.5 megohms after a spell of humid weather, it appears that some attention to leakage conditions might be in order.

We felt that it would be interesting to compare our dc results with J. W. Gratian's work on erase assymetry, (*3) so have changed his data to a db basis and replotted it in figure 3. He states that his results are applicable to bias fault as well as to erase. Both curves seem to have essentially the same shape, but Gratian's work seems to reflect much greater sensitivity. We are not sure, whether this stems from the greater effect of assymetry, or whether the use of an entirely different oxide is the cause.

In any case, we agree with Gratian's observation that bias assymetry may be neutralized in effect by the addition of proper amount of dc of correct polarity. Perhaps some broadcasters using home machines for remote pickups might use this idea to improve their signal to noise ratio. While noise may be created by poor erase waveform as Gratiain shows, we find that much of this noise is erased by the bias flux.

Another source of noise is permanent magnetization of the recording head as a result of transients in the signal. A machine may start the day with a signal to noise ratio of 61 db and be down to 54 db by night, due to this effect. Hence, professional machine manufacturers recommend frequent demagnetization of the recording head. Usually they can supply equipment for doing this, and some machines have built-in demagnetization means. If you cannot secure a demagnetizer from the manufacturer, you may wish to have one built, like figure 4. Most of the dimensions are not critical, but the radius on the tips of the poles must be a good fit to the curvature of the recording head. The coil may be either random wound, or layer wound with .0015" glassine between layers.

To use, plug into 115 volt AC, and apply pole tips to recording head. Slide sideways and gradually remove from the head. Do not connect to the power line for over 10 seconds at a time, for the coil overheats with great rapidity.

Recording heads should be demagnetized at least once a day for good results, and twice a day if the best signal to noise ratio is desired.
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Wolfgang Kuhn, Assistant Professor of Music

Located high at the back of a large recital hall, in a remodeled projection room, is one of the most compact - and one of the busiest recording rooms in this country. It's the new, centralized recording installation of the University of Illinois School of Music.

Here, transcriptions are made from the stage of the Recital Hall - or from any class room or rehearsal room in the entire school. And facilities permit instant playback of any recording to whatever room it originated from. In addition, recorded music as well as live radio programs can be channeled directly from "headquarters" to any of the class rooms, as an aid in teaching and learning the performance of music.

This installation also serves as a remote control room for the University Radio Service, WILL, which carries weekly programs performed by the faculty and the students, and by the various choral and instrumental organizations of the School of Music.

The University of Illinois School of Music is collecting a permanent file of past programs for reference, class-room use and future broadcast. Works already on file comprise one of the largest and most representative collections of contemporary music - as performed, during the annual Contemporary Arts Festival, by the U. of I. Sinfonetta and Orchestra, conducted by John M. Kuypers, director of the School of Music, the Walden String Quartet, and other ensembles, choral groups and famous guest artists.

The recording studio was installed last March (1949), and has been under the able direction of Wolfgang Kuhn, Assistant Professor of Music. Since then, the demands for service from this department have increased so rapidly that now, besides Mr. Kuhn, two engineers spend most of their time at the controls.
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By M. W. Jeffers WFAA Recording, Dallas, Texas

In 1946, Station WFAA, Dallas, decided to improve their recording room set-up - to provide the Southwest with the last word in modern high-fidelity sound recording facilities. Plans were drawn and redrawn - ideas exchanged - innumerable conferences held. Here is the cumulative result of more than two years of planning and construction - a room 19' by 13', filled to capacity with the most modern recording equipment, including 6 racks, 4 recording machines, 2 dubbing and playback tables and record-storage space. While the equipment is fairly conventional in itself, the finished layout is of particular interest from the standpoint of appearance, performance and operational features.

The entire system was designed for high quality and high fidelity from beginning to end. Each piece of equipment was thoroughly inspected and tested. Distortion, frequency response, gain, etc., were measured before installation, resulting in overall performance that leaves little to be desired.

Fig. 1 shows a partial view of the equipment from the entrance - including three of the six racks and two of the four disc recorders. The other two recorders are on the opposite side of the room, and the dubbing and playback tables (shown in Fig. 2) are located at the left, adjacent to the entrance. A combination record storage and desk is located at the right of the entrance. The racks are installed over "wells" across the rear of the room, with three feet of space between wall and racks to allow ample room for maintenance work.

The recording room receives its programs from poly-cylindrical studios via a 12-feed, 6-channel master control room. Four program circuits are normalled to the selective switch system located on each recording table. One other program and two phone circuits are available to be patched at will.

Since all recording channels are identical, only one will be described in detail. Across each input is a preset master-relay-operated switch system. This feeds a 50,000 ohm to line bridging coil - then to the limiting amplifier (only 3 db or less of compression is used). The high bridging-coil impedance is used so that all four recording channels can be placed across one 500-ohm program source without any impedance upsets. The limiter feeds a volume control with a VU meter across the output, located on the recording table for convenience. Next, a relay operated by a cutter switch, also on the control panel, allows program tone to be interrupted to each individual head without affecting any other, should more than one channel be across a single source. The NAB recording filter and head equalizers follow, and feed the 40-watt Altec recording amplifier which feeds the temperature-controlled RCA MI-U850C recording head.

A monitor amplifier and speaker are connected across each recording head, to permit checking circuit continuity, noise, distortion, etc., at the last possible point before it goes on the disc. The frequency response of this amplifier has been modified to complement the recording pre-emphasis. NAB recording standards are used and closely maintained.

Racks 2, 3, 4, and 5 are all identical - like the two left-hand racks shown in Fig. 1. Equipment consists of (top to bottom) : recording amplifier, jack strips, band-pass filter, limiting amplifier, bridging coil, recording equalizer, monitor amplifier and relays. Rack 6, at right in Fig. 1, contains (top to bottom) meter for tube checks, utility circuit, pre-amplifiers, transmission measuring set, jack strips, audio oscillator, program amplifiers and power supply for preamps and roving monitor amplifier. This amplifier, together with a 15" Altec 604 high-fidelity speaker, can be switched across any program circuit in the recording room.

Fig. 3 shows a close-up of one of the four Scully recording machines. On table at front (left to right) are the motor start switch, control panel and recording-head heater switch and pilot light. On the post behind the carriage is the channel VU meter and attenuator. The large box on the wall behind the machine houses a metal sack made of #80 mesh brass hardware cloth, to catch the removed cutting thread. Each machine has its own separate thread collector.

A Spencer central suction plant housed in another part of the building furnishes suction for all four machines. A valve located beneath each thread collector controls the suction at the individual machine.

The dubbing channel equipment illustrated in Fig. 2, is interesting in that the turntables are mounted on Neoprene rubber cups set on a 6" platform mounted on 1" cork. This is done to eliminate building vibration. The entire assembly is so constructed that the turntables are waist high, for convenience in operating from a standing position. The dubbing channel circuit, shown in Fig. 4, consists of two preamplifiers feeding a two-position mixer and a high-pass filter to further eliminate any possible effect of building vibration on the discs being dubbed. The program amplifier supplies the same signal (+ 8 V U) output as the master control, allowing any or all recording channels to be bridged across it.

The heads were selected after exhaustive tests on all leading high-quality pickups on the market. These heads, with a modified arm and an equalizer of our own design, provide reproduction of the NAB recordings within ±1db from 30 to 10,000 cycles.

• Anmerkung : Das war für 1950 ein ganz toller Frequenzbereich bereits im Hinblick auf die neue UKW-Technik, die ja 40 bis 15.000 cyles können sollte.

The excellent low-frequency response of the pickups led to the extreme steps necessary to eliminate the effects of building vibration. Amazing even to us, was the fact, that the pick-up that gave the best results was a relatively low-priced, high impedance unit.

However, after equalizing and matching to low-impedance, the output was still within limits as to output (-63db).

The equalizer circuit, shown in Fig. 5, excels anything tried, which included every one we had ever seen or heard of - even equalized amplifiers.

After installation was complete and circuit continuity was established, frequency and distortion runs (with pre-emphasis) were made on the complete channels. The overall response is ±2db within 30-16,000 cycles and ±1db, 20-20,000 cycles, without the limiting amplifier.

The distortion is less than 1/2% of 1% over the frequency range. Next, the heads were connected and exhaustive runs were made by actually cutting the frequency runs and checking the resulting cuts by the light pattern method. Equalizers were installed and adjusted until less than ±1db variation resulted between 800 and 10,000 cycles. The preemphasis equalizers were then inserted and frequency runs repeated until the recorded results were well within NAB limits. A frequency run from a resistance capacity oscillator through the recording channel, played back through the dubbing channel and measured on a distortion meter showed a maximum of 1% distortion for all the equipment involved.

Periodic frequency runs and distortion measurements are made, and each needle and disc is noise tested by actually playing and measuring the test cuts on the dubbing channel.

A routine check of the overall system noise level revealed the following: After recording continuously for 9 hours on each of the four recorders, one was picked at random and the playback noise from a test cut, as measured on a "G.R." Noise Meter, showed a -50db noise under normal program level of 6c.m. stylus velocity. Needles used were Audio's Microgroove No. SM 14, and the disc, of course, was a Red Label Audiodisc.

. . . with five important advantages to all professional recordists

Plastic-base, red oxide Audiotape is now available in professional-size, 2500 foot rolls - wound either on standard NAB aluminum hubs, or on complete aluminum reels. This latest addition to the Audiotape "family"" offers these five significant advantages.
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• 1. Exceptionally Low Cost. Audiotape Type 2551H (on hub only) has a list price of $10.00. Audiotape Type 2551R (on completed reel) has a list price of $12.85. These prices, of course, are subject to the usual discounts to dealers, radio stations, recording studios, schools, and industrial firms. Note that the additional price for the aluminum reel is only $2.85 list.
• 2. The full measure of 2500 feet gives 4% more tape than the usual 2400-foot reel.
• 3. There are absolutely no spliees in the entire 2500-foot roll. It's guaranteed to be all one piece.
• 4. Audio Devices also guarantees that volume deviation within a 2500-foot reel, at 1,000 cps, is not more than ± 1/4db - and not more than ±1/2db from reel to reel. These are outside limits - not averages!
• 5. A unique, specially-designed package (patent pending) makes handling and storage of the tape much easier and safer than ever before - especially when used or stored on the hub alone.

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The new Audiotape package is illustrated in detail in Figures A, B, and C.

The outside section of the container is made of stiff, durable cardboard, while the folded-over inner section which holds the tape is of rigid corrugated board to provide extra stiffness for easy handling. One side of the inner section has a wide slot, as shown in Fig. B, while the other side, shown raised up in Fig. C, contains a wooden core which fits snugly into the aluminum hub. To transfer a roll of tape on the hub from the box to the horizontal turntable of a professional recorder, it is only necessary to hold the inner container and tape in the position shown in Fig. C - place it over the turntable hub, and then slide the container out from under the tape.

• Anmerkung : Das Magnetband war - nicht nur für die Firma AudioDevice - völlig neu, der Umgang damit auch und nicht alle Bediener waren sich des Risikos bewußt, wenn der offene Wickel auseinander bricht oder fällt, durch Dummheit oder Unachtsamkeit. Für die Neulinge wäre das eine große Katastrophe. Darum ist die in den Bildern gezeigte Aussparung unter dem Bobby rund um den Mitnehmer auf den Wickeltellern eine große Hilfe, den Bandwickel einigermaßen sicher auf das Gerät zu bekommen.

In this way the tape itself is firmly supported at all times, and there is no danger of its slipping from the hub or becoming unwound. After use, the roll of tape on the hub can be easily returned to the container by reversing the above operation. Simply slip the slotted side of the container under the tape, then fold over the other side until the wooden core engages with the hub, and it's all ready to pick up and slide back into the box.

Conversion from hub to reel is also greatly facilitated by this unique container. Side flanges can be screwed onto the hub while it is still in the container, as shown in Fig. D and E. With the slotted portion down, simply place the flange over the hub and drop the bottom halves of the three sleeve screws into place as in Fig. D. Then fold the solid portion of the container down onto the reel. This will hold the sleeve screws in place and the container can be turned over so that the flange is on the bottom of the roll. Then lift up the slotted portion, place the top flange over the hub, and insert the other halves of the sleeve screws, as in Fig. E. There's no danger of dropping the screws, or letting the tape slip from the hub. The side flanges from a complete reel can also be easily removed from the hub while the tape is still in the container.

When the tape is stored on the hub in the container, it hangs from the fixed hubcore so that the tape does not rest on itself. Thus, there is no danger of flattening the bottom of the roll or damaging the edges of the tape. And since reel flanges can be attached to the hub so quickly and easily, it saves the expense of storing tape on the reel, even when complete reels are required for use on a particular machine.

The new Type 2551 Audiotape is packed 5 boxes to a carton, and is now available through local Audiotape and Audiodisc suppliers all over the country.

March, 1950 by C. J. LeBcI, Vice President, - Audio Devices, Inc.

As every experienced engineer has found, it is not possible to make a
product which is the ultimate in every single respect, because many properties are achieved only at the expense of others. In short, a good design is one in which conflicts have been resolved to yield the best overall performance. The cellulose acetate we use for a tape base material is no exception to this rule.

It will be recalled that two years ago we discarded vinyl copolymer base, and adopted cellulose acetate, because the desirable properties of the vinyl were attained at the expense of too many faults. Cellulose acetate seemed to have a better balance of characteristics, and time has verified this judgment.

There are a number of grades of cellulose acetate (die verschiedenen Qualitäten), differing in the degree of plasticizing (Elastizität). The minimum amount of plasticizer produces a hard, brittle (sprödes) material. Increased amounts increase the flexibility, until finally a very soft, rubbery (gummiartige) characteristic is produced.

In choosing our base material it was necessary to conform to NAB standards, and this indirectly fixed the thickness of the base at .0015 inches. Adequate strength had to be provided, in this thickness. Normal recording machine tension would have to produce as little permanent stretch as possible, otherwise the program would take longer to reproduce than it should. At the same time, the material would have to withstand the shock of rapid machine reversal, so that impact strength was also necessary.

These stringent requirements ruled out the heavily plasticized acetate, leaving only the light and medium plasticizing to be compared. Recording-wise, the medium grade was preferable, for its improved flexibility allowed the tape to maintain better contact with the head, a guaranty of better high frequency response and smoother motion through the machine. The question was, would the strength prove adequate?

Upon measuring the permanent stretch with various loads, we were surprised to get the result shown in figure 1 . Both minimum and medium degrees of plasticizing produce the same permanent stretch at all loads up to 2.5 lbs., and the curves diverge only above that value. At higher loads the greater resilience of the medium plasticizing allows more stretch. We can better evaluate these
results if we recall that normal recorder tape tension is of the order of 1/4 to 5/8 lbs.

The peak tension during reversal (Rücklauf), machine manufacturers tell us, is never over 1 1/4 lbs. In the normal working range, then, the two acetates stretch identically. At heavy peak loads the medium material can give resiliently, where the light would prove too brittle.

Since the breaking strength for both materials was in the 4 1/2 to 5 lb. range, we standardized on the medium plasticizer content.

It is interesting to note that the breaking strength of tape is seven to twenty times the normal working stress. This is a factor of safety worthy of the bridge builder, and certainly very conservative.

A New Idea In Tape Recording That Has Been Made Into a Flourishing Business.

A little more than two generations ago a bride posed rigidly with her new husband to the tune of "Hold it - Hold it" while a camera took endless minutes to record her new state for posterity.

Today there is a new wrinkle in such portrait taking. A young army veteran has set up shop under the name of "Magnetic Recording Company" and is making a lively business of taking what he calls "Portraits in Sound".

• Anmerkung : Ein Army Veteran ist nicht immer ein in das Rentenalter gekommener Soldat, das kann auch ein ganz junger Mann sein, der die Armee verlassen hat.

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No fly-by-night, Art Foy, who spent nearly four years as a technical adviser in the Army Airways Communications System, is fast becoming a respected young businessman in his community.

His friends call him a recording demon. No matter what he has to work on and no matter how adverse the circumstances - which usually refers to acoustics - he manages to iron out the difficulties and come through with a high class professional recording. Like the time he boarded the New Columbian of the B&O Railroad and recorded its initial run along with the complete ceremony, or recording in a huge cathedral where echoes are everywhere. Thus the phrase of "Magnetically Recorded by Foy" has come to be used.

Although unmarried, he seems to be particularly fond of recording weddings, and he likes best to take his wedding "Portraits in Sound" when the couple is unaware that they are being recorded. "I always get a kick out of their exclamations of surprise when they find out that Mom and Dad had the foresight to have the whole thing recorded. They always want to know where on earth I had the microphones!"

Art and his staff take pride in the places they manage to conceal their microphones. "We choose our spots well, and sometimes we are like a bunch of kids hiding Easter eggs." Art has been using egg-size microphones but now that he has found one the size of six dimes stacked up, he is in recorder's seventh heaven.

Whether he is recording a wedding, a college concert, a speech or an operetta, he makes it a point to be on hand an hour or so before the event and have his equipment completely set up and out of sight with his tiny microphones hidden in plants, chandeliers, behind vases or what have you, and even though the performers know he is on the spot, they are completely unaware of his presence. One chance remark overheard while leaving a church following a wedding still has Art patting his back. One lady said to another "I couldn't hear the
bride and groom at all", with the reply of "Oh, well, we'll hear them when we hear the recording".

Art, who fell in love with radios at the age of eight and was operating his own hand-made ham station fully equipped with an FCC radio license at the age of fourteen, and was one of the first amateur radio operators on the air in the U. S. occupied zone of Germany, now has his own radio shows over Evanston's AM and FM stations. On WEAW, called "On-the-Spot", many of his recordings are aired and also on WNMP called "Your Church Choir" plus special feature shows where on the spot recording is necessary. He also works with WOAK (FM) in Oak ark and has weekly transcriptions aired on WCFL in Chicago.

Art likes to point out that his business is possible only because of the great advancements that have been made in the high-fidelity recording field. "Just think", he says, "Out in Des Moines right now a radio station may be playing a record of a church choir that was tape recorded in a Columbus, Ohio church and then sent to me to be made into a disc recording. That sort of thing makes a guy in the recording business feel that he is well, you might say," he finished ruefully, "helping to knit the people of the United States closer together."

Sitting in his place of business at 1465 Sherman Avenue, Art surprisingly declared, "My studio is portable." He explained that instead of having people such as singers, speakers, musical instrumentalists, or choral groups, come to him to make their records, he preferred to go to them on their home ground where they can feel perfectly natural and at ease. As he facetiously pointed out, "You know if it's their piano that shows up with an out of tune note on the recording, they can't blame me."

His customers are particularly pleased to find out that tape recordings can be played back right away; the sour spots found and erased. Thus, they may repeat their performance over and over until they are completely satisfied and then have the final approved recording transferred to a 10 inch or 12 inch record to be preserved.

When Art recorded the almost two hour long Sonja Henie Ice Show he learned a new trick. Any show he records for later airing he edits very carefully, selecting the highlights and cutting out mistakes to make a jam-packed thirty minute show. He found that to splice tape is wasteful since it can be erased and re-used; so he hit on the idea of working the Sonja Henie show where any time. Here. Mr. Foy sets up his by recording the parts desired on another tape - the result, no tape wasted.

Art and his recording equipment are a familiar sight at school and college musical and dramatic productions. But he gets the biggest thrill from recording younger children in their recitals and activities. They are tremendously interested in his equipment to begin with and then, as he says, there is no greater fun than standing back and observing their expressions when they hear how they sound on record. Art explained. It's this way - "Here is little Janie who plays the violin and at home she really doesn't sound so very good, but mom keeps her practicing.

Yet, when she gets to school with all the others in the band or orchestra they begin to sound really good. Well, when Janie takes home a professional record of her playing she has a definite pride of accomplishment and the record has invoked in Mom and Dad at home an interest far deeper than before. Janie practices harder, too. That sort of thing makes me feel like I'm helping build our community in a small way. Guess I just like children anyway," he said. Mothers who have discovered that their wax recordings of Junior's lispings to Santa or the Easter Bunny made by department stores can be put on a permanent 10 inch record are losing no time in bringing their cardboard discs to Art.

Tight spots are no novelty to Art. At one large concert, he could not find a place for an overhead microphone which was needed to pick up the orchestra and choir. Not at all stumped he quickly canvassed the neighborhood and found a house wife who was willing to lend him her much beknotted clothesline. He hurried back to the church and before the guests arrived he had the clothesline nestled cable-fashion among the rafters out of sight with two microphones pinned on it. We learn as we go along, he said, and now a clothesline is a permanent part of his equipment.
.

Art laughingly recalls one of the first weddings he worked on. He recorded the ceremony and submitted the tape recording for approval before making the 12 inch discs. "I knew this was one time I had
wasted a lot of effort ; no one would buy a recording as full of extracurricular noises as this one. Imagine my surprise! They smiled at the airplane roaring into the middle of the prayer; they chuckled when the dog barked as the soloist sang, and they laughed outright when the fire engine broke into their vows, as it clanged by the church windows." They wanted the recordings just as they were. He has found that such noises practically sell the recording. One young bride laughed and laughed when she identified the clunking sound, as her
father stumbling against the pew (Sitzbank) as he stepped back to his place after giving her away.

The son of a Methodist minister (hier "der geistliche"), Art has no trouble finding his way about in churches. Ministers and Priests often chat with him. They all seem to like the idea of couples having the opportunity to hear their vows at leisure and without the strain of the wedding day. As one minister said, "There might be a much less chance of couples separating if they had the recording of their vows to listen to at times of marital strife.(ernsthafter Ehe-Streit)"

Art recorded his first wedding in 1935 as a stunt to surprise the bride and groom. The married couple's pleasure gave him an idea as to just how successful recording weddings could be. And today he is certainly proving it. "After all," he says, "recordings aren't any more expensive than a set of wedding pictures and listening to yourself is just as much fun as looking at yourself."

The problem of surface noise has long been a "headache" to professional as well as amateur recordists - particularly the progressive increase in noise as the cut approaches the center of the disc.

Audio Devices' chief chemist, George M. Sutheim, has now found a practical solution to this problem - by perfecting an improved lacquer formulation that gives lowest surface noise at all diameters. And the variation in noise level is only about 2db from 3" to 11" recording diameters. Other discs normally have a variation of about 10db between these same limits.

This important development, now in full production on all Audiodiscs, will be discussed in detail in the next issue of Audio Record.
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by C. J. LeBel, Vice President, - Audio Devices, Inc.

Our subject for this month is somewhat of a departure from the usual technical aspects of recording. It is a very important one, however, and we believe it will be of interest not only to educational recordists, but also to others who are concerned with the problem of making good recordings under unfavorable conditions.

The writer recently had an opportunity to speak to a group of high school teachers; this was followed by a short research project with Prof. William J. Temple of Brooklyn College, reported on at the recent Eastern Public Speaking Conference. The contrast between these two activities was so great, that an article seemed desirable.

After watching the high school teacher at work, looking over his equipment, and hearing the acoustical performance of his studio (the classroom), only one conclusion is possible: he is trying to do a man's job with, almost literally, boys' tools.

The work with Prof. Temple indicated that a recorder which is to be useful in all speech applications must have surprisingly wide frequency range. In general, an educational recorder is not used to show the well trained teacher the student's faults! It must reproduce the student's mistakes of diction, etc., clearly enough so that the student himself can hear them clearly. The outcome is a need for uniform response to at least 7.5 kc. This is one aspect of the faithful vs. pleasing reproduction debate that has gone on for years. Very clearly, the teacher needs photographic realism, complete faithfulness, in his recording system.

Such a degree of faithfulness cannot be achieved by using an ordinary home recorder bought from the most persuasive salesman - it calls for a professional machine and professional accessories.

The average classroom is so reverberant (hallig) that its use for recording can be condoned (gedulded) only by custom (Gewohnheit). If you have such a room, heavy (fireproofed) drapes, spaced several inches from the wall, can reduce the fault if not eliminate it. The only fundamental solution is to have an acoustical contractor treat the room.

If the classroom is too reverberant, it is almost mandatory to use a unidirectional microphone of the cardioid or super cardioid type. This will at least minimize the pickup of reverberation. To use the ordinary inexpensive omnidirectional microphone often supplied with the recorder is merely to compound the original acoustical error. If the microphone has a high impedance output, it can even be used to feed the most inexpensive home recorder directly. If the microphone has only a low impedance output, matching transformers are obtainable that can be fastened directly to the microphone cable.

When making a dramatic-class recording, it is heart breaking to try to get proper balance of cast and effects with a single microphone, and lost time or a poor performance surely will be the outcome. Two microphones and a two-position mixer would save a lot of time and trouble. If standard professional technique is to be used, a third microphone and mixer position for the announcer would be desirable. All of this makes it desirable to provide a control room where the program balance can be set properly. Monitoring through headphones is not a good way to maintain the balance of a complex production.

We conclude with a pair of sharp remarks. The first is a paraphrase of a bit of Prof. Temple's recent article in "Audio Engineering" magazine. You cannot convince a student that he lisps if the recording machine itself suffers from a permanent lisp. Secondly, we seem to be going through a cycle very similar to that pursued during the early days of educational disc recording.

At first, the educators bought the cheapest home type machines. Finding results disappointing, they changed to better and better professional machines. Today, the average educational disc recorder is of thoroughly professional quality. In the magnetic recorder field, the colleges have already begun to change to the $500-$800 class of professional machine, and it is only a question of time before the high schools do the same. History seems to repeat itself with annoying regularity.

........ with magnetic recording tape.

The Swiss have a name for it. They call it the "Ipsophone". We call it one of the most ingenious applications of tape recording that we have seen so far. In fact it "thinks" - "remembers" - and has the audacity to talk back, too!

Briefly, the Ipsophone - a Swiss invention - is an automatic telephone answering device that records messages on magnetic tape and plays them back later, when called for. No "operator" is required anywhere along the line, where dial systems are in use. Here's how it works.

You have an urgent call to make to your friend, Mr. Jones. You dial his number. If he doesn't answer after the first three rings, Ipsophone swings into action and a recorded voice says, "Hello, hello. This is the residence of Mr. Jones. Your message is being recorded automatically. Ready! Please speak now." And if you're not too surprised to remember what you wanted to say, you go right ahead and give your whole message, just as if Mr. Jones were there himself.

Then, when Jones gets home, he calls the Ipsophone number. As before, the tape recorded voice answers, saying "Hello, hello. This is the residence of Mr. Jones. Your message is being recorded automatically. Ready!" Right there (before it says "Please speak now") Jones breaks in, saying "Hello, hello." That makes the Ipsophone change its mind, and instead of recording a message, it automatically plays back the part of the tape that you recorded, giving your message, in your own words, exactly as you said it.

The operation described so far is a fairly simple one. Where it gets really complicated - and quite ingenious - is in the system which enables one master Ipsophone to handle many different subscribers, yet keep messages strictly confidential, to be played back only to the individual for whom they are intended. If you want the confidenual service, your telephone is provided with a code key, on which you set a secret combination of code numbers known only to yourself. Then, when you call Ipsophone for a message, it automatically reads off a series of numbers, beginning with zero - stopping for 4 seconds after each number. You simply say the magic words, "hello, hello", after each of the code numbers you selected. Your message is then transcribed back to you from the tape, as before. However, if anyone tries to "break" your code, and misses a single number, he either gets a busy signal or is disconnected. You can change your code numbers as often as you want, so there's practically no possibility of anyone "breaking" your code.

The Ipsophone recording mechanism is a compact and complicated assembly of telephone relays, timing devices, sequence switches and other sensitive electronic equipment - arranged for proper control of the multiple tape recorders.

Although a newcomer to this country, the Ipsophone has already found extensive use abroad (im Ausland). Department stores use them for recording after-hours orders. Banks use them to take important massages after closing time. The "Geneva Journal" uses them to record messages from foreign correspondents all over the world - as also does Reuters, the British news agency. In fact the Ipsophone is being widely applied for most of the applications where we, in this country, have been using a personal telephone answering service. Ipsophone, however, has the added advantage of absolute privacy - plus the infallible accuracy of a tape recording.

We may see - and hear - a lot more about this telephone recorder. For an American corporation is making arrangements with the Swiss company to massproduce thousands of them over here. So don't be too surprised if your next telephone message is automatically recorded on tape.

From a two year program of groundwork in which disc recordings played a major role, the University of Tennessee began FM broadcasting on October 27, 1949, with WUOT, 3000 watt outlet. A series of eight weekly programs, most of them disced with Rek-O-Cut heads on
Audiodiscs, was started in the fall of 1947 when Kenneth D. Wright came to the University from ten years in commercial radio.

Wright organized a student Radio Workshop and produced the eight shows weekly on various subjects of adult information. Usually the programs were recorded and mailed to out of town stations in Tennessee. In 1948 the series was expanded to ten programs weekly, one of which was awarded an honorable mention in the Ohio State Exhibition of Educational Radio Programs. This show, "Songs of the People," was recorded on Audiodiscs and broadcast on WBIR in Knoxville, Tennessee.

With the heightened interest in radio and the growth of the Radio Workshop, the University constructed WUOT this year. Operating five and a half hours daily, Monday through Friday, the station offers fine music, drama, news, discussions, documentaries, and popular music. One of the major principles behind the station is to experiment with in-school listening programs for elementary' and high schools of East Tennessee with a vievv- to expanding this phase later. The station is operated with student personnel, directed by two professionals.

WUOT now has two Brush Soundmirror tape recorders, used primarily for student training and occasional remote spots, two Rek-O-Cut cutting heads, M-5, used for auditions and rehearsals, and a Fairchild Unit 539G for discs to be used on WUOT and commercial stations.

All of the informational programs on commercial stations in the state, now numbering seventeen periods weekly, are grouped under the general title of the University of Tennessee "Campus of the Air." With the four-fold purpose of AM extension programs, operating WUOT, student training, and experimentation in classroom listening, the Radio Department of the General Extension Division has undertaken a full program of bringing more mature radio from the campus of the state university.

by C. J. LeBel, Vice President, - Audio Devices, Inc.
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Shortly after the end of the war (2. WEltkrieg), a number of our best customers began clamoring for a better lacquer-formulation especially designed for use as a master. This would have noise level at the inside diameters as low as at the outside, but the wear resistance could be slight.

• Anmerkung : Das bedeutet doch im Umkehrschluß, vor und während des 2. Weltkrieges war der Rauschpegel auf den Innenbereichen der Aufnahme-Platten nahezu unerträglich hoch gewesen, wenn "ein paar" der wichtigsten Kunden eine deutliche Verbesserung der Lackzusammensetzung - also der Qualität der leeren Rohplatten - angemahnt hatten.

Work on this project began in 1946 and was carried on intensively. By 1948 prewar microgroove development had been revived, and the pressure for something became still more intense. A considerable number of master formulae were developed and tested, but they all had one fault or another. Perhaps the worst was a tendency for the cut groove to become noisy in time. The more miraculous the groove quietness, the worse this effect became.
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Emphasis finally shifted to a reproportioning of our standard formula as our faith in the magic of any one new ingredient dropped to zero. As is well known, a recording lacquer contains many ingredients, and the optimum proportions are found by experiment rather than by theory. Hundreds of tests were made, and in the summer of last year the reproportioning led to an interesting master formula. It was as quiet at the inside as at the outside, and it had none of the bad habits which the radically new developments had been cursed with. Particularly, there was no tendency for the cut groove to become
noisier with time. The groove would withstand only three playings, but this was no fault in a master.

• Anmerkung : Also - eine ganz frisch geschnittene Platte konnte bis zu 3 mal abgespielt werden. - Dann war sie vermutlich nicht mehr brauchbar, so weich war diese Mischung.

When we began to think of production we ran into an obstacle: It is not easy to change lacquers in our coating system, for the pipes have to be emptied of lacquer, then cleaned thoroughly. Since the demand for masters is small, this would have involved shutting one lacquer system down for a day to permit a day's run on masters, or else installing an additional fabulously expensive stainless steel pipe system to be used a small part of the time. Either method would have led to very high costs.

• Anmerkung : Es gab also unterschiedliche Roh-Platten zum Aufzeichnen/Aufnehmen. Das waren einmal die Master zum Vervielfältigen und die normalen (general purpose) Leerplatten zum "live" Aufnehmen und (aber nur) mehrfach Senden.

At that point it occurred to us that most of the improvement might be incorporated in our regular formulation. Tests were made, and it appeared that most of the master quietness could be incorporated in a general purpose lacquer without sacrificing wear resistance or any of the other good properties. Pilot runs were made and the results tested successfully by a number of leading recording organizations, so in the late fall we started to modify the production formulation slightly in the direction indicated. As everyone seemed pleased, and the complaints were nil, more and more modification was used, with a field test of each change before it was put into production. By mid-January 1950 we had gone over completely to the new version.
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The present formulation has been used continuously since then, and any discs in your stock will be of the latest type, or within 90% of it.

Figure 1 shows the noise characteristic of the modified lacquer, for a standard
transcription groove (also die breite dicke 78er Rille). Since it is very easy to keep a groove quiet at diameters of 12 to 16 inches, we have started our graph at 11 inches. For comparison, data on two other makes of disc is included, with all three tests run with the same stylus.

Figure 2 shows the result of a test under microgroove conditions, using a micogroove stylus instead of the standard model used in figure 1.

In both graphs the reference velocity is 8 cm/s, and the speed of rotation 33.3 rpm. Standard NAB test conditions were observed, except that the reproducing stylus radius was in accord with the type of groove to be reproduced.

The tests show, that a standard transcription groove in AUDIODISC is practically as quiet at 7" diameter as at the outside. Other makes have not done as well. In microgroove the problem is more difficult, but here, also we have succeeded in greatly reducing the increase. So, the signal to noise ratio is better than 30db from 5 inch diameter out, and better than 55 db from 6 1/2 inches out. As the curves show, this is a significant improvement. In other respects - long wear, good thread-throw, stability of noise level with time, foolproof processing, and humidity proofing, the characteristics are unchanged.

While touching on the subject of microgroove noise, it might be well to mention something noticed on many discs sent in for criticism : The average newcomer to microgroove work cuts much too fine a groove. Whereas 70:30 "groove:land" ratio is considered necessary, these brave souls are cutting 40:60 "groove:land". Apart from the serious increase in noise which results, such a groove will not be tracked reliably in many home reproducers. So, avoid an excessively fine groove. The added recording level which it would permit only causes excessive tracing distortion, which is responsible for the fuzzy sound (on peaks) of so many microgroove discs.

If we may be permitted to moralize, it is interesting to note that the result was obtained by using Buckner Speed's old "method of the 10%" - by pyramiding many small improvements - after the trial of "miracle ingredients" and radically new materials had wasted much time with no success.

Here, In one of Manhattan's leading studios, musically talented technicians turn out top quality recordings for discriminating clients.

To most people, the word "Muzak" brings to mind soft lights and sweet music from the strains of Brahms or Beethoven to the latest hits from Broadway shows, accompanied by the clink of cocktail glasses. And a menu that says "Music by Muzak."

Actually, the Muzak Franchise Service - the wired music so familiar to patrons of finer hotels and restaurants throughout this country, Canada, Mexico, Hawaii, and Puerto Rico; and to employees in many industrial plants and business offices - is but one of Muzak's diversified recording operations.

Another, very familiar to the radio field but not too widely known by the general public, is Muzak's Associated Program Service. This up-to-the-minute "Basic Library" of scripts, sales aids, and recorded music is a vital and continuing source of high quality musical program material for broadcasting stations from coast to coast. More than five thousand recorded selections are available in this library - and new ones are continually being added and distributed to subscribing stations on a "lend-lease" basis.

Keeping these two transcription services supplied with top-quality recordings is a man-sized job of itself. Yet it is but a part of the work handled by the Muzak Transcription Division. Their recording studios, located at 151 West 46th Street, just off Times Square, make no claim to fame as the largest of their kind. But they are one of the oldest and newest in existence - old in years of service to the recording art and experience of their personnel; new in ideas and equipment for the modern recording application.

In addition to turning out all recordings for Muzak Franchise Service and Associated Program Service, the Transcription Division handles a wide variety of special work for broadcasters, industrial firms, government agencies, music societies, educational institutions, program producers, and advertising agencies. They also recorded and processed and pressed all Silvertone Records - distributed nationally by Sears and Rocbuck in addition to many
nationally known independent labels.

The main recording studio, conveniently located on the ground floor, is big enough for a concert orchestra, and contains a full complement of percussion equipment - from a Hammond organ to chimes and kettle drums. The walls of the room are provided with a combination of fixed and adjustable baffles which enable the engineers to obtain any desired acoustical effects for any recording applications, from full orchestra to one or two voices. At one end of this studio is the control room - considerably more spacious than most, and with all controls at the fingertips of the recording engineer.

Immediately behind this is the studio recording room, containing the disc recorders for cutting the original studio masters. All of these masters are cut in duplicate, using vertical rather than lateral recording. The inherent advantages of the vertical recording provides a studio master of as life-like quality as it is possible to obtain. Although all pressings for the Franchise Division and Associated Program Service are vertical, the original masters for the other types of discs are recorded vertically, and then dubbed from vertical to lateral on Audiodiscs for manufacturing and distribution purposes. In so doing, it is felt that the final recording is of superior quality.
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The central control room - virtually the nerve center of the entire department - is located on the floor above. Here a large master control panel, designed by their own engineers, measures the pulse of every operation going on in any of the various recording rooms. A unique feature of this panel is the fact that all circuit elements are in duplicate, with provision for automatic and instantaneous changeover in case of failure of any unit. Also located in this room is another bank of disc recorders for dubbing and cutting master Audiodiscs from tapes and other recorded sources.

As far as the actual recording equipment goes, the Muzak studios are not greatly different from those of other major recording firms. Muzak, however, takes particular pride in the experience and background of their personnel.

The type of work handled covers the complete range of the recording art - turning out everything from 16" studio transcriptions to special 3" records for a novelty item - from conventional to microgroove recordings - from tape to special wire recordings for mobile equipment.

The Muzak Transcription Division makes all of its own virgin vinylite pressings from exclusive formulations developed and manufactured in their plant, and they have recently opened a new and ultra-modern processing and pressing plant in Kentucky. The processing masters are shipped to the plant in specially designed containers which assure safe arrival
at their destination.

The Muzak philosophy, if you could call it that, could probably be summed up as follows:

Recording is both a precise science and an art. As such it requires the finest precision equipment, and the artistic skill of recordists who know both their subject and their medium. Having these things. It is no great problem to maintain the highest standards of recording quality with minimum lost motion - and with minimum wear and tear on the client.

Mrs. Neta Kaye Stolcely's Personalized Discs Delight Youngsters from Coast to Coast

It all began with an idea. The idea that children's story-records could be made much more interesting if they were given the "personal touch." And putting this idea into practice has enabled Neta Kaye Stokely (Mrs. Roy Stokely), of Oklahoma City, Oklahoma, to develop a unique and profiable recording business that she conducts in her own home, in her "spare time."

Now - instead of just listening to ordinary recorded stories about mythical fairy-tale characters - youngsters can hear about themselves, their pets, their play-mates, and interesting events in their own lives.

At the start, Mrs. Stokely decided to try out the idea with her own two children, Craig and Jean. So, calling upon her own extensive background of radio broadcasting experience, she wrote a couple of short fairy tales, with Craig and Jean as the principal characters. These were recorded on tape and transcribed onto 10" discs. The records made a big hit with the youngsters.

They would listen by the hour. They brought their friends in to listen, too - and their friends brought their friends. It wasn't long before the news was all over town - and Mrs, Stokely found herself with a flood of orders on her hands. Other parents wanted records about their "kids", too. They supplied the information - names of the children, their pets, their playmates, and their habits (both good and had). These Mrs. Stokely skillfully wove into the same basic story patterns she had first developed - one about "The Galloping Butterfly" and the other about "The Absent Minded Cricket."

From this simple beginning, Mrs. Stokely has expanded to a profitable mailorder business, with customers in practically every state in the country. The extent to which her fame has spread is indicated by the fact that she was recently featured in the "Interesting People" section of The American Magazine. Purchasers fill out a "MY OWN STORY" questionnaire order form, giving the pertinent information about the child for whom the record is intended. Mrs. Stokely does all the rest - "personalizing" the story, making the original tape recording, and having it transcribed onto an unbreakable ten-inch disc.

Normal delivery is about two weeks - the cost, $3.50 per record. Readers who are interested in this unique recording service can obtain complete details and questionnaire order forms by writing to Neta Kaye Stokely, 1620 Northwest 44th St., Oklahoma City, Oklahoma.

Mrs. Stokely makes all of her original recordings on Audiotape, right in her own home, using a portable tape recorder. She has found that she can record about five stories an hour. The tape is then sent to a local sound studio, which transcribes it into disc form so that it can be played back on any home phonograph.

The convenience of magnetic recording tape - its ease of editing and erasure - have done much to help make this venture so successful. Mrs. Stokely says: "I'm so thankful there are such things as tape recorders, or my little project would be much more difiicult to execute. Three cheers for Audiotape."

by C. J. LeBel, Vice President, Audio Devices, Inc.

Three years ago the writer scribbled an indignant article for the "Audio Record", bewailing the old tradition of secrecy in disc recording (and other branches of audio engineering), a tradition which was keeping it in the class of an ancient craft. It was felt that the time had come to turn a craft into a profession.

Well, three years have passed, and much has happened. We now have a professional society devoted entirely to the audio engineering field, and its local sections meet monthly to discuss audio engineering matters. We have had the first Audio Fair, the first audio convention ever held. Nevertheless, a great deal more remains to be done.

With the encouragement of the Audio Engineering Society, we have seen free verbal discussion of audio problems become generally accepted. It is not hard to get speakers on an audio subject. Everyone seems willing to share his ideas with his immediate neighbors, and this is a vast step of improvement over several years ago. But how about sharing them with the whole country?

Ah, that is where the battle starts. After a year or two of prodding, poking, and pushing, it may be possible to extract an article for publication, or again it may not.
Audio engineering will not become a full fledged profession until free publication becomes as well established as free discussion. We will have to make publication as automatic in our field as in the older field of radio engineering. One of the earmarks of the medieval craft was it willingness to exchange ideas within the town, and its complete lack of interest in sharing ideas with other towns. By this token, recording is still a craft.
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Now that our readers have been thus prodded, we hope to see more contributed papers on recording problems in the "Audio Record" and elsewhere.

Here are a few subjects that need more attention than they have received in print in the past:

• 1. Tape recording bias - there is too wide a gap between theoretical explanations of rf bias operation, and the actual rules of thumb used in the field. These rules are simple, but they lead to irreconcilable results if applied to nominally identical oxides whose bias-output curves differ even slightly.
• 2. Tape recorder maintenance - how often should heads be demagnetized or cleaned, or clutches adjusted? How about noise reduction compensating voltages?
• 3. Tape recorder operation - how about a more extended discussion of editing time savers?
• 4. Disc recording styli - there is too much disparity between published data on improved stylus characteristics, and experimental results. More experimental results should be published.
• 5. Hot stylus process - What experiences have you had with this new method of cutting? What average and maximum stylus life is achieved?
• 6. Recording room layouts - In my travels a lot of nice ideas are encountered, but nobody is energetic enough to write about his improvements.
• 7. Speech input system improvements - these also need more attention.
• 8. Finally, how about circuit ideas and convenient gadgets?

The "Audio Record" would welcome articles in its field. If you have some more fundamental thoughts, the Audio Engineering Society would welcome a chance to consider them for publication. Such manuscripts should be sent to the Audio Engineering Society. Box F, Oceanside, N.Y.

We are looking forward to hearing from you.

We have received a number of inquiries as to the best method of applying paper labels to Audiodiscs. In all such cases we recommend the method used at our factory, for it has been successfully tested on several million Audiodiscs. Also, it is a method that can easily be used in any recording studio or at home, without any special equipment.

First, lightly soak the label in a small quantity of solvent, such as acetone, which can be purchased in any drug store. Even nail polish remover can be used if desired. After soaking, the excess solvent should be removed by drying the label between the folds of a handkerchief.

When all free liquid has been absorbed but while the paper is still moist, carefully apply the label to the disc surface. When dry, the label becomes permanently affixed to the disc, as the lacquer itself serves as the "adhesive".

It should be noted that lacquer solvents, such as acetone, must be handled with caution, as they are highly inflammable. Also, it must be remembered that if any solvent is dropped on the surface of a disc it will damage the surface and make it unsuitable for recording at that point. We therefore suggest that this procedure be practiced on a few old discs that have no further value, before using it to label new recordings. Once the technique has been mastered, it will be found extremely simple and effective.

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