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SECTION I GENERAL OPERATION
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CROWN guarantees this equipment to perform as specified. CROWN also warrants the components and workmanship of this equipment to be free from defects for a period of 90 days from date of purchase.

This warranty does not extend to fuses, and/or component or equipment damage due to negligence, misuse, shipping damage or accident; or if the serial number has been defaced, altered or removed.

An application for a FREE 3 year WARRANTY TITLE is included with this manual. Upon receipt of this completed form, CROWN will issue the Warranty Title - subject to the conditions contained therein. This title applies to the original end-purchaser and will be issued only upon the receipt of the application.

We urge that you take full advantage of this coverage - fill in and mail the application now!

Your IC-150 is to be heard! Let's hook-up the unit quickly, but properly (and we'll assume a CROWN D-150 as your power amp).

I. Check your front panel
Set: A Selector Knob at Phono 1
B Volume to counter clockwise level
C Balance to 12o'clock NORMAL
D Panorama to counterclockwise NORMAL
EF, GH Bass and Treble to FLAT 12 o'clock

ALL BUTTONS MUST BE IN THE RELEASED POSITION
Now plug in the AC Cord.

II. Connect:
A. your record player to the IC-150 inputs
B. the AC from turntable to the unswitched outlet on the IC-150
C. your amp - preamp cables (supplied with IC-150).
D. power amp cord (using a 3-to-2 wire adapter).
E. We trust that your previously connected speakers have in-line fuses as shown.

III. Calibration:
A. Turn off the left and right levels of the amp.
B. Start favorite record on the turntable; push AC on IC-150.
C. Turn up IC-150 volume to about 3 o'clock.
D. Turn up amp left and right levels until you have normal volume.

IV. Your new "IC-150 Sound" on time.
A. Sit back and enjoy the sound.
B. Get further acquainted and read on!!!

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• - Selector knob - Phono 1 & 2 - for turntables, inputs have 50-70 db gain, 47K ohms impedance and max. sensitivity of lmv @ lKHz.
  Tuner - for FM Stereo/stereo multiplex or AM/FM Tuner.
  AUX 1 & 2 - any device which can be connected to the AUX inputs i.e. microphones, guitar, additional tuner, additional tape recorder, electric razor, etc.
  Tape 1 & 2 - for tape recorders with 2 or 3 head configuration.
• - Volume - Adjust volume for your entire system.
• - Balance - Acts as a built-in equalizer for proper balance of your system.
• - Panorama - when in "Normal," music plays in stereo. "Mono" - for mono application. Each speaker puts out the same sound. "Reverse" all signals are switched. Signals which appeared in left channel will appear in right channel and vice versa.
• 1. Push for Loudness - when engaged adds loudness compensation to volume control; disengaged - response is flat at all volume levels.
• 2. Tape 1 - when engaged - monitors previously recorded material on Recorder 1.
• 3. Tape 2 - when engaged - monitors previously recorded material on Recorder 2.
• 4. Low Filter - eliminates low frequency noise or rumble when engaged. Disengaged - flat response.
• 5. Hi Filter - eliminates high frequency noise such as record scratches; disengaged - flat.
• 6. AC - turns on the complete system.
• 7. Push for Flat - engaged - cancels all tone control effects for perfectly flat response. It does not cancel scratch or rumble filters.
• E-F - Bass Controls - inner knob controls bass prominence on right channel; outer knob, left channel.
• G-H - Treble Controls - inner knob - controls treble prominence on right channel; outer knob, left channel.

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Any associated power amplifier(s) should be powered from the accessory AC sockets on the IC-150, not the wall socket. Use three-to-wire adapter(s) as contained in the IC-150 accessory kit. - CAUTION: DO NOT connect the Green (ground) wire(s) of the adapter(s) to the IC-150 chassis!!!

Reason: The signal (shielded) cables from the IC-150 output(s) to your power amplifier(s) carry the ground(s). Connecting the adapter green-wires will cause "ground-loops" with resulting hum, oscillation and possible amplifier and loudspeaker damage.

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1. SELECTOR Rotary Seven Position Switch when operated chooses the sound source and recording source from phono, tuner, tape player, or recorder, TV sound, guitar amp, etc.
2. The VOLUME control with over 60db of dynamic range adjusts listening level of the program through your speakers. It does not affect the program fed to tape recorders. Notice the excellent channel-to-channel balance as the volume is raised or lowered.
3. BALANCE control usually remains at 12 o'clock for equal volume in each speaker. Turn the control toward the weaker channel to correct for unbalanced sound.
4. PANORAMA control supersedes the conventional mode selector-switch. You may smoothly vary the "stereo-image" from normal full stereo at "7 o'clock", toward mono, at "12 o'clock", then out to reverse-stereo, at "5 o'clock". This control helps reduce "ping-pong" stereo - particularly when using headphones.
5. BASS controls are continuously variable ±_ 15db at 30Hz and are normally at 12 o'clock for "flat" response. Turn clockwise for increased low-frequencies, counterclockwise for decreased bass. (The larger control affects the left channel while the smaller, projecting knob controls the right. Each control is independent but may be easily operated in tandem by grasping both inner and outer knobs.)
6. TREBLE controls are continuously variable + 15db at 15 KHz and are normally at 12 o'clock for "flat" response. Turn clockwise for increased high-frequencies, counter-clockwise for decreased bass. (The larger control affects the left channel while the smaller, projecting knob controls the right.)

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1. TAPE MONITOR 1 and TAPE MONITOR 2 provide instant replay from the "monitor" playhead of one or two typical 3-head recorders. In other words, you can listen to what you just taped.
2. LOW FILTER Button when depressed will roll off low frequencies at a 6db/octave rate below 50Hz (3db down-point). Sub-audio rumble is therefore reduced, without materially affecting the sound you hear.
3. HIGH FILTER Button when depressed will decrease the high frequencies at a sharp 12db/octave rate beginning at 5000Hz (3db down-point). Distorted, worn, and scratchy records benefit most with minimum loss of essential response.
4. ON-AC Button when depressed applies power to the IC-150 and simultaneously powers any component plugged into the switched AC outlets on the rear apron. Additionally, muting of the IC-150 output occurs for about four seconds after turn-on - thus eliminating "thumps" caused by most solid-state components. (NOTE: components not switched on by the ON-AC Button may not be muted unless turned-on within the four-second period.)
5. PUSH for LOUDNESS Button when engaged boosts bass and treble tones with respect to midrange tones at low sound levels. The amount of boost increases as the level drops. Disengaged, response remains flat (except for tone control and filter effects) at all sound levels.
6. PUSH for FLAT Button, when depressed, cancels all boost - or cut-action of both the BASS and TREBLE controls. Tone controls may therefore be "in" or "out" at a touch.

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Your IC-150 has many versatile capabilities. Of course, we cannot give all the possible combinations which Hi-Fi users can dream up, but the following are a few examples:
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• 1. USING THE SELECTOR AND TAPE RECORDER(S).
  
  
• A. To hear a tape being played on Recorder 1, you may turn the SELECTOR to Tape 1 or push TAPE MONITOR 1. See Figure A.
• B. To hear a tape being played on Recorder 2, you may turn the SELECTOR to Tape 2 or push TAPE MONITOR 2 See Figure A. (WARNING - Do not leave a Recorder in "Source" then turn IC-150 Selector either to or through that Recorder as oscillation will result.)
• C. To record any source onto Recorder 1, turn the SELECTOR to that source. As an example, to record a disc being played on. Phono 1 turn SELECTOR to Phono 1, you can even record the play-back from Recorder 2 by turning the SELECTOR to Recorder 2. After setting the selector, please place Recorder 1 in the source mode and push TAPE MONITOR 1. Adjust Recorder 1 input levels, then adjust the output levels until volume is unchanged whether TAPE MONITOR 1 is depressed or not Begin taping, then switch the source-tape switches of Recorder 1 to "TAPE" releasing and depressing the TAPE MONITOR 1 will now yield the "Source-Tape" A-B comparison. You can also leave the TAPE MONITOR 1 depressed and A-B the recording at the machine. See Figure C.
  As with Recorder 1 described in C, any source can be taped on Recorder 2 including playback of Recorder 1. Further, any source on the SELECTOR (except Recorder 1 or 2) may be taped on both recorders simultaneously and monitored individually using TAPE MONITOR 1 OR 2 (if 1 and 2 are depressed together, 2 will override 1).
• E. While taping on Recorder 1, it is also possible to listen to a completely different tape on Recorder 2 by depressing TAPE MONITOR 2. As TAPE MONITOR 2 overrides TAPE MONITOR 1, for easy monitoring we suggest method E; however, the following method may be used.
• F. It is possible to record from any source on the SELECTOR with the exception of Tape 2 onto Recorder 2 while listening to Recorder 1. First, set-up Recorder 2 as in C above. Second, to hear Recorder 1 playback, disengage TAPE MONITOR 2 and engage TAPE MONITOR 1.

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• Anmerkung : Dieser Teil ist aus meiner Sicht absolut überflüssiges Marketing Gequakel. Ich habe mit dieser Panorama Funktion einmalgespielt und dann nie wieder. Daraus nur 2 A4 Seiten zu generieren, ist reines Papier vergeuden.

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An important part of the unusual flexibility of the IC-150 is illustrated in Fig. 1-6 The pictures show the variation in balance (relative source levels of the two channels) and the stereo image (locations from which the sounds seem to be coming) available through use of the BALANCE and PANORAMA controls.

The musical example pictured has a piano (it looks like Peter Nero's) in the left channel, accompanied by a singer (probably Robert Goulet) in the right channel. Starting at the left, both controls are shown in the NORMAL position. With this setting it is possible that the musical source, the reproducing equipment, and the surrounding acoustics will together allow the piano and voice to sound balanced (i.e. neither isobscuring the other) and distinctly separated in distance (i.e. perhaps the singer appears to be in the middle of the stage while the piano is off to the left).

If this is true, the controls can be left in the NORMAL position and life is astonishingly easy. Imagine, however, that a poorly made recording gives you the feeling that the singer is performing on your patio off to the right, while the piano is being played in your neighbor's lawn across the street to the left. This is too much separation.

By moving the PANORAMA control toward the MONO posi-tion(see below) you can move the two channels together until you are satisfied with the sound. Moving all the way to the MONO position mixes the two channels completely, giving no separation (i.e. the singer will be sitting on the piano a la Dean Martin). If you would rather have the piano on the right and the singer on the left, this can be accomplished by turning the PANORAMA control to the REVERSE position, as in the third picture.
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The next row of pictures illustrates the effect of moving the balance control toward the left position. Suppose that after listening to the music, it seems to you that the singer is dominating the piano too much. By turning the balance control toward the left position you can decrease the vocal contribution from the right channel until you feel satisfied with the relative levels of piano and voice.

If you want to hear only the piano, turn the BALANCE all the way to the LEFT position, at which point the singer (right channel) will be turned off completely, and the piano will continue alone on the left. If you then move the PANORAMA control toward the MONO position, the piano will seem to move toward the right. At the MONO position, the sound of the piano will be coming at equal volume levels from both speakers. If you turn the control toward the REVERSE position, the piano will move further to the right, until it appears solely in the right channel. The piano has duplicated its movement in the top row of pictures, but without the vocal accompaniment.

The last row of pictures shows the same process in the right channel. Perhaps you decide that the singer needs more emphasis. Turning the BALANCE control toward the RIGHT will decrease the piano volume until the relative levels are satisfactory. At the RIGHT position, the piano (left channel) will be completely gone, and the singer will appear alone in the right channel. You can then use the PANORAMA control to move the singer to any position between the right and left channels, as shown in the succeeding two illustrations.

Notice that in the three pictures showing the PANORAMA control in the MONO position, that the sound comes from a single location between the speakers regardless of the BALANCE control position. This occurs because the BALANCE control appears before the PANORAMA control in the circuit, an arrangement which means that the BALANCE control does not operate on the mixed signal coming from the PANORAMA control.

It also means that any BALANCE change will affect both speakers equally when the PANORAMA control is in the MONO position. If, for example, you decrease the sound of the piano by turning the BALANCE control toward the RIGHT, the sound will decrease equally in both speakers. The need for flexibility dictates this design.

Using the level controls on your power amplifiers still allows you to vary the sound level from both speakers if you want, while the location of the BALANCE control before the PANORAMA control allows you to vary the levels of the individual channels before mixing is done by the PANORAMA control. This way, the BALANCE control and the amplifier level controls do not merely duplicate each other, but accomplish different functions, thereby adding another dimension to your control of the music.

The result of the IC-150 is an unparalleled capability for fitting your music, components, and environment together in a satisfying way.

The external muter shown in Figure 1-5 is a very simple device to use. As a suggestion, the switch could be conveniently installed beside a telephone, thus eliminating the risk of falls when running at high speeds from the stereo to the telephone.

By installing a single pole, single throw, "on/off" type switch with any length of "zip cord", remote muting may be achieved.

To install, simply loosen the hex nuts on the muter, remove the jumper wire installed by the factory. Wrap either wire attached to the switch to either lug on the muter then retighten the external muter nuts. (See Figure 1-7)

There are four basic ways to display your IC-150: custom mounted, mounted in the accessory 5-D walnut cabinet, standard 19-inch rack mounted, or free standing in its attractive vinyl "tuxedo."

CUSTOM MOUNTED - A full size template of the IC-150 is enclosed in the rear of the manual. This template also includes dimensions for the shelf which is recommended.

ACCESSORY CABINET Your IC-150's appearance for shelf or table mounting will be enhanced when installed in the model 5-D walnut cabinet.

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1. A-B Test.
   Evaluating relative performance of two (or more) components or systems by changing quickly from one to the other. Most high fidelity dealers have A-B test facilities.
2. Acoustic or Mechanical Feed-back
   An annoying low frequency interference created when vibrations from loudspeakers are picked up by the cartridge and amplified by the sound system. Physically separating loudspeakers and record-playing equipment will solve the problem.
3. Channel ...
   A channel is a complete sound path. A single channel, or monophonic system, has one channel. A stereophonic system has at least two full channels designated as left (A) and right (B). Monophonic material may be played through a stereo system; both channels will carry the same signal. Stereo material, if played on a monophonic system, mixes and emerges as a monophonic sound.
4. Crossover ...
   A frequency at which other frequencies above and below it are separated. In a two-way speaker system, for instance, the crossover frequency is the point at which woofer and tweeter response are divided.
5. Crosstalk ...
   Signal leakage between two channels.
6. Damping ...
   Controlling of vibrations, response, or resonances which if unchecked would cause distortion.
7. Decibel ...
   A numerical expression of acoustic or electrical ratios, such as the relative intensity of a sound or the relative strength of a signal. One to three decibels (db) is about the smallest change in sound perceptible to the ear.
8. Distortion ...
   Unwanted noise, or sounds which didn't exist in the studio when the original recording was made. Harmonic distortion disturbs the original relationship between a tone and other tones naturally related to it.
9. Intermodulation distortion (IM)
   introduces new tones caused by mixing of two or more original tones.
10. Phase distortion, or non-linear phase shift
    disturbs the natural timing sequence between a tone and its related overtones.
11. Transient distortion
    disturbs the precise attack and decay of a musical sound. Harmonic and IM distortion are expressed in percentages; phase distortion in degrees; transient distortion is usually judged from oscilloscope patterns, but is best measured as phase distortion.
12. Equalization ...
    Frequency manipulation to meet the requirements of recording, and an inverse manipulation on playback to get uniform response. Also known as compensation.
13. Flutter ...
    Rapid variations in the speed of a turntable or tape transport. When pronounced, flutter causes a wavering of musical pitch.
14. Hertz ...
    As in cycles-per-second, it is not the car-rental agency.
15. IHF Music Power:
    this rating expresses the ability of an amplifier to handle short duration power peaks, as opposed to sustained power levels. An amplifier may onlybe capable of putting out 45 watts if that level is continuous, but it may be able to handle 60 watt peaks (such as might occur in a musical passage), if the peaks do not last too long.
16. IHF Noise Measurement:
    any of 3 defined ways to measure noise, each of which uses a different filter, or frequency-weighting method, in making the test; usually the IHF "A" weighting is the reference, since this measurement simulates the Fletcher-Munson loudness curves, and is therefore insensitive to high and low frequency noise. This method produces the largest signal-to-noise specification.
17. Phon:
    a unit of loudness for steady tones, correlated with the Fletcher-Munson loudness curves, and referenced to the db level at lKHz. 100 phons equals lOOdb at lKHz, while 100 phons at 100 cycles is about 103db (cf Fletcher-Munson curves shown in discussion of loudness control).
18. Signal-to-Noise Ratio ...
    Often abbreviated as S/N ratio; the proportion of signal to undesired and extraneous noises in any device or its output. The higher the ratio, the better. Expressed in decibels.

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1. FREQUENCY RESPONSE Hi-level: ±0.6dB 3Hz-100 KHz with hi-impedance load, ±0.1dB
   10Hz-20KHz with IHF load; Phono: ±0.5dB of RIAA, calibrated
2. PHASE RESPONSE : Hi-level: typically +1° to -12° 20Hz-20KHz with IHF load;
   Phono: typically ±5° 20Hz-20KHz additional phase shift
3. HUM AND NOISE : 20Hz-20KHz inputs shorted; Hi-level: 90dB below rated output
   (typically lOOdB with IHF "A" weighted measurement; Phono: 80dB below lOmV input) typically 0.5uV input noise
4. DISTORTION THD : essentially unmeasurable; IM: less than 0.01% at rated output with IHF measurement (typically under 0.002%)
5. INPUTS : five hi-level inputs (1 tuner, 2 auxiliary, 2 tape) two equalized
6. phonos
7. INPUT GAIN & IMPEDANCE : Hi-level: 20.8dB ±0.2dB, 100K ohms; Phono: 50-70dB (adjustable) 47K ohms. Sensitivity: lmV @ lKHz for rated output.
8. PHONO INPUT OVERLOAD : 33-330mV at lKHz, depending on gain (lOOmV when set to 60dB total preamp gain)
9. OUTPUT 10V maximum before overload, 2.5 rated, 600 ohms output impedance
10. PHONO OUTPUT & IMPEDANCE (at tape out) 600 ohms with typical maximum output of 9v RMS at lKHz into hi-impedance load
11. VOLUME CONTROL over 60dB dynamic range with calibrated tracking
12. LOUDNESS COMPENSATION : new wide-range design for excellent simulation of Fletcher-Munson curves down to 60 phons; with exclusive dual R/C bass-boost coordinated with volume control
13. PANORAMA CONTROL : unique, continuously-variable control for infinite adjustment from stereo to mono to stereo-reverse, replaces confusing conventional stereo-mode switches and blend controls with the first intuitive control of stereo spatial dimension.
14. TONE CONTROLS continuously variable ±15dB at 30Hz and 15KHz, cancel switch bypasses independent bass and treble control settings to give instant true-flat response in both channels
15. MUTING uses plug-in reed relay - removes turn-on transients from IC-150 output thus protecting speakers
16. FILTERS Rumble: -3dB at 50Hz with 6dB-per-octave cut-off, Scratch;-3dB at 5KHz with 12dB-per-octave cut-off
17. AC OUTLETS four switched with 25A switch, one unswitched
18. POWER REQUIREMENTS about 2 watts at 120v or 240v 50-400'Hz AC
19. SEMICONDUCTOR COMPLEMENT two integrated circuits (equivalent to 42 bipolar transistors and 2 FET) for a total of 54 bipolar transistors, three FET, three zeners and seven diodes
20. DIMENSIONS 5 1/4" H x 17" W; 8 1/4 behind panel - WEIGHT 10 lbs., with walnut cabinet 16 lbs.

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• I.1 All warranty and guarantee clauses become void upon payment of invoice.
• I.2 Dimensions will always be expressed in the least usable terms. Velocity, for example, will be expressed in furlongs per fortnight.
  
  
• II.1 Identical units tested under identical conditions will not be identical in the field.
• II.2 A dropped tool will land where it can do the most damage. (Also known as the law of selective gravitation.)
• II.3 The probability of a dimension being omitted
• from a plan or drawing is directly proportional to its importance.
• II.4 Interchangeable parts won't.
• II.5 Probability of failure of a component, assembly, subsystem or system is inversely proportional to ease of repair or replacement.
• II.6 If a circuit cannot fail, it will.
• II.7 A fail-safe circuit will destroy others.
• II.8 A transistor protected by a fast-acting fuse will protect the fuse by blowing first.
• II.9 A failure will not appear till a unit has passed final inspection.
• II.10 A purchased component or instrument will meet its specs long enough, and only long enough, to pass incoming inspection.
  
  
• III.1 Manufacturers' spec sheets will be incorrect by a factor of 0.5 to 2.0, depending on which multiplier gives the most optimistic value. For salesmen's claims these factors will be 0.1 or 10.0.
• III.2 In specifications, Murphy's Law supersedes Ohm's.

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The performance specifications for the CROWN IC-150 have hit some new lows: witness in particular the low distortion and low noise. Also in the interest of your audio happiness, the unit has been engineered to provide precise handling of all types of music, and the controls allow you to fit that handling to your own best taste. The following performance now belongs to you.

INPUT AND OUTPUT SPECIFICATIONS
The availability and functions of the different inputs and outputs have been incidentally described in earlier parts of the manual. A few more details with a bit more organization seem to be in order.

Altogether there are seven inputs available covering turntables, tape decks, tuners, and whatever you want in the auxiliary inputs. Particular facts about these inputs include the following:

• HI-LEVEL
  The five high level inputs (tape, tuner, aux) show an input impedance of 100K ohms. The gain from these inputs to the main outputs is set at 20.8db ±0.2db (i.e. with the volume control at maximum, 0.5 volts in will get you about 5.5 volts out).
• PHONO
  The two phono inputs have been equalized to match the RIAA standard response curve. Their input impedance measures 47K ohms. In order to adapt to different turntables and cartridges, the gain of the phono preamp has been made adjustable between approximately 30db and 50db which adds to the main preamp to give a total gain, of 50-70db (lKHz). Two small screwdriver-adjusted pots, mounted on the back of the unit next to the phono inputs, provide the means of separately adjusting the gain of each channel.
  
  The phono level controls are set during the final factory check of the IC-150 to give a total preamp gain of 60db. This setting in the middle of the range proves satisfactory for most stereo cartridges. The gain adjustment should not usually have to be altered. Situations which may require gain adjustment include voltage overloading from unusually high voltage cartridges, low tape-output levels from cartridges with unusually low voltages and cartridges with unbalanced channels. The level controls may also be used to balance the volume levels of different inputs to the IC-150 (i.e. to match the level of the turntable to the level of the tuner, etc.).
  
  In general, phono overloading should not be a problem. Depending upon the gain setting, the overload point will vary. If the phono gain is turned to its maximum of 50db, a signal of 33mv will produce about 10 volts out, which is the maximum available. With the gain turned to its minimum of 30db, it takes 330mv in to produce the maximum 10 volts out. The phono overload level therefore varies between these two limits. At the factory setting of approximately 40db, the overload level is about 100mV.
  
  To demonstrate the range this gives, consider the case of a fairly standard phono cartridge with an output of 8mv at a needle velocity of 5.5 cm/sec. An LP record may produce peak velocities of about 30 cm/sec, which will in turn produce maximum voltages from the above cartridge in the range of 45mv. At the preset phono gain of 40db, the maximum cartridge output remains substantially below the overload voltage of 100mV.
  
  The comparative signal levels at input and output appear graphically below. The comparative level chart gives some sample signal levels and shows the range of gain available in the phono preamo as well as the main preamp.
• MAIN OUTPUTS
  The main outputs are rated at 2.5 volts, with a maximum output of 10 volts. Output impedance measures 600 ohms. In the event that the IC-150 is employed to drive a 600 ohm load, it will typically produce 5 volts rms into this impedance.
• TAPE OUTPUTS
  The tape outputs (output of the phono preamp) typically produce 9-10 volts (rms) maximum output at lKHz into a high impedance load. (In the following discussion of frequency response, a graph of the typical maximum phono output from 20Hz to 20KHz is included.) These outputs also show a 600 ohm output impedance.
  
  We get music into and out of the IC-150 through the avenues just considered. Next is a description of what happens to the music between the inputs and outputs.

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Hi-Level:
±0.6db 3Hz-100KHz with hi-impedance load (1 meg, Opf.).
±0.ldb 10Hz-20KHz with IHF load (100k parallel with lOOOpf)
Phono:
±0.5db from RIAA standard response curve.

No electronics equipment gives all frequencies equal treatment. If you look at some frequency response graphs, you will notice that the usual pattern for audio equipment shows deviations from the set level at high and low frequencies - depending on the equipment, there may be other deviations in between.

To get the information for these graphs, the test level (usually 1 watt output for power amps, and rated output voltage for preamps) is set at lKHz (1000Hz).

The test signal frequency is varied above and below this frequency, and the resulting changes in output level are graphed according to the frequencies at which they occur. The term "flat" indicates the set level. An amplifier "flat from 20Hz to 20KHz" is one which does not deviate significantly from its set level between the frequencies indicated.

Any departure from the flat level simply means that, at the frequency where the departure occurs, the equipment is amplifying the signal either more or less than it is amplifying the lKHz signal.

If the response is down 2db at 50Hz, the 50Hz signal is getting 2db less amplification than the lKHz signal. Depending on circumstances, you can probably detect a change of from 1 to 3db in sound intensity, which means that a 2db drop in the low frequency range would be noticeable in a production where low frequencies were an important part of the music. The ideal then would be a completely flat response curve over the entire range of audible frequencies (about 20Hz to 20KHz).

Theoretically, a piece of equipment will retain its frequency response at all levels from the test level to its rated maximum level. In real life, theoretical projections have a way of passing away like the morning dew.

And so it happens that some power amplifiers which perform beautifully at 1 watt levels will self-destruct if extreme frequencies (20Hz or 20KHz) are delivered to them at their rated power levels. It is sometimes very worthwhile and informative to look at a power response test as well as the usual frequency response test for amplifiers.

Preamps live among similar limitations and a good response curve at the rated output level (for the IC-150, this is 2.5 volts), may fall apart when the record you are playing through the phono input is trying to push the preamp output to 8 volts at 15KHz.

The IC-150 has been designed to maintain its ability to produce clean, high level signals even at the extreme frequencies of the audio range. A maximum response curve of this sort is shown below along with the usual response curve taken at 2.5 volts out.

Part of the information on the response graph is the RIAA response of the phono preamp. The title doesn't help much but this is simply a response curve taken through the phono preamp by itself instead of through the main preamp.

Because of the way records are cut, they do not have a flat frequency characteristic. In the light of this situation, phono preamps need a special compensating response curve that is not flat. The RIAA (or Record Industries Association of America, the organization that sets up standards for phono response so that everyone's records can be played on everyone else's stereo systems) response indicates what should come out of the preamp when a record is played through it.

The response of the preamp should cancel the effects of the record-cutter so that the resulting output is flat with the frequencies balanced as in the original production.

We have just told you that the ideal response curve at which everyone aims is perfectly flat from 20Hz to 20KHz. Now we're going to tell you something different.

Unfortunately (and this is why good audio systems may end up with a bewildering array of knobs, switches, buttons, and other special effects), this is not ideally true. In fact, the most desirable response at many sound levels is not flat at all, and your own personal tastes (i.e. do you like drums or piccolos better?) may decree that your desired response will not be flat at any listening level.

But so that you have a good foundation upon which to operate in satisfying your own musical tastes, it is necessary to have a flat response to begin with. From this point, you can move out according to the dictates of your own ears, by using the loudness control, tone controls, and filters. The loudness control compensates for a characteristic which appears in everyone's hearing, while the tone controls and filters are planned to adjust the sound to fit your audio equipment, your music, and your tastes.

Without the loudness compensation, the volume control should preserve the frequency response (shown above) anywhere in its range. In other words, the response should duplicate the above graph whether you are listening to a high or low volume level.

At fairly high levels (comparable to a good seat at a live performance), this is fine because the balance that you hear between the different tones approaches the balance of a live performance.

But as you turn the volume down, it becomes evident that the low frequencies and the high frequencies fade from your hearing much faster than do the mid-range frequencies. This phenomenon derives from the non-uniform response of your ears.

Please don't assume we're insulting your ears. It is simply true that at low sound levels, you do not hear low and high frequency tones as well as you hear mid-range tones. The set of curves below shows how your hearing changes
with frequency change. These curves were obtained by having a group of listeners compare tones of other frequencies with a lKHz reference tone.

The other frequencies were increased in loudness until the listeners felt they were as loud as the reference. This particular set of curves comes from the research of men named Fletcher and Munson (from which derives their highly imaginative title!).

As a particular example, observe that the line which crosses the 40db line at the lKHz frequency climbs to the left until it reaches the 78db level at 30 cycles. This indicates that the 30 cycle tones would have to be boosted by 38db to maintain equal loudness with the lKHz tones at this sound level.

The loudness compensation circuitry of a preamplifier provides this boost in the low and high frequencies in order to make the loudness of each frequency match the loudness of the lKHz tone. When the loudness compensation is engaged (by pushing the loudness button), the volume control then affects the loudness according to the curves shown above with greater bass and treble emphasis occurring as the level is turned down. At low levels, then, the actual response is no longer flat but what you hear will sound flat because you've got human ears. Clever, right?

The loudness control is largely a response to the natural character of everyone's hearing. The tone controls and filters on audio equipment are more personal. They exist to enable you as the listener and final critic to mess around with the sound of your system until you like it.

The controls are reasonably named in accordance with their function. The bass control makes it possible for you to increase or decrease the level of bass you are hearing. The treble control similarly handles the treble tones.

Besides these controls there are two buttons designed to cut down the bad effects of some system problems. The rumble (low) filter acts to eliminate unwanted low frequencies that may appear in your system (through the turntable mechanism, for instance). The scratch (high) filter acts to eliminate high frequency peculiarities (such as scratches on your records). Use of these filters necessarily cuts down the high and/or low frequency response, but this in some cases sounds much better than listening to the faithful reproduction of turntable indigestion or the results of record torture by bouncing tone arms.

The curves shown for these controls give an idea of their effect on the program being passed through the preamp. The curve labels are intended to show where the control knob should be set to result in a given amount of increase or decrease in sound. Full boost on the bass, for example, means the bass knob will be turned all the way clockwise (to about the 5 o'clock position). This will add 8db to the 100Hz signal. The 50Hz signal will be boosted 13db and the 20Hz signal will be increased by 22db. One-half boost curves apply when the control knob is turned approximately half way between the flat position and the full-boost position. Going the other way, the bass control will lower the volume of the bass end of your program. The treble end can be emphasized or cut back similarly by use of the treble knobs.

Depressing the "PUSH FOR FLAT" button cancels the effects of the tone controls (but not the filters).

The low filter drops the output 3db below the flat level at about 70Hz, which, as a point of reference, appears at the low end of the range of a cello. (This is affected by the setting of the volume control, with maximum filtering occurring at full volume when unwanted low frequencies are most likely to be audible).

A loss of 3db in output level represents a fifty percent loss of power (but not necessarily a 50% loss in loudness). The filter then cuts off frequencies below 70Hz at a rate of 6db per octave, which means that the level drops 6db each time the frequency goes down by one-half (i.e. there will be a 6db drop between 40Hz and 20Hz, etc.). A 6db loss cuts the power by a factor of 4.

The high filter hits its 3db down point at 5KHz. For reference, the high end of a piccolo's range is about 4.2KHz. Above this, the filter cuts the signal at a rate of 12db per octave, (i.e. the power will drop by 12db, or a factor of 16, between 6KHz and 12KHz, etc.).

Hi-Level: typically
+1° to -7°, 20Hz-20KHz with hi-impedance load, or
+1° to -12°, 20Hz-20KHz with IHF load.
Phono: typically
±5° additional phase shift 20Hz-20KHz.

This particular characteristic of audio systems has not been much emphasized. Its effect is not easy to describe accurately, since poor phase response does not produce the obvious aberrations heard with high distortion or bad frequency response.

The need for good phase response appears with the desire to hear musical instruments sound as they do in the concert hall. Each instrument has its own peculiar sound, made up essentially of the particular note being sounded plus its harmonics. If the middle A on a piano is being sounded, for instance, the fundamental tone (and first harmonic) is 440Hz. The second harmonic is 880Hz, the third is 1320Hz, and so on. The particular sound of each instrument derives from the relative amplitudes of the various harmonics associated with the fundamental tone. For example, if the second harmonic is much louder than the third harmonic, the note will sound different than would the same note with a louder third harmonic. That's why trumpets and piccolos and police whistles don't sound the same, even if they can hit the same note.

Any change in the relationship of these harmonic tones to one another and to the fundamental will produce a change in sound. Suppose, for example, there is a 45° phase shift between the lKHz tone and its fourth harmonic, the 4KHz tone. This would, in effect, slow the 4KHz tone down by 1/4 of a cycle, and force a different combination with the fundamental tone and the other harmonics. This would change the waveshape of this particular note, and consequently the sound you heard when the waveform hit your eardrum. In order to preserve as much as possible the original sounds of the instruments to which you are listening, the total phase distortion of your audio system should be as low as possible. For a given amplifier or preamplifier, it should be less than 15° across the audio bandwidth of 20Hz to 20KHz.

Total Harmonic Distortion: essentially too low to measure.
Intermodulation Distortion: with IHF load less than 0.01% at 2.5 volts out.
(typically less than 0.002% at 2.5 volts) (typically less than 0.004% at 10.0 volts)

Harmonic distortion measurements have customarily been used to evaluate the performance of audio equipment. The preceding note concerning phase response made reference to the importance of harmonic tones in musical sound. Harmonic distortion figures show the degree to which a piece of audio equipment changes a signal by adding harmonics to it. (To make the test, a signal known to have a very low level of distortion is introduced at the input of the unit under test.

The resulting output (usually at the rated output level of the equipment) is then compared to the input to determine what percentage of harmonic tones has been added to the original signal. This test is repeated at several frequencies in the audio band (20Hz - 20KHz), and the amount of harmonic distortion is graphed on a frequency scale.) The drawback to this type of test lies in the fact that such distortion can actually sound pleasant. In the same way that phase distortion can change a sound without making it unpleasant, harmonic distortion can change the harmonic makeup of a tone without offending your ears, since the additions to the original tone arrive in harmonic intervals.

Intermodulation distortion is a different breed of cat. Instead of adding harmonious sounds to your music, it deals in sum-and-difference frequencies.

For instance, a 100Hz tone from a bass clarinet might modulate a 1000Hz tone from a violin to produce a 900Hz signal (the difference between the two frequencies), and an 1100Hz tone (the sum of the two signals). The resulting sound has all the endearing qualities of a piano smashing contest, and none of the benefits (i.e. piano smashing is good clean fun and it gets rid of some bad pianos).

Besides showing up a more unpleasant type of distortion in audio equipment, IM distortion measurements relate more directly to crossover distortion, a problem especially troublesome in transistor amplifiers. On the whole, therefore, IM distortion measurements constitute a more valid means of evaluating audio equipment. In making the IM test, signals of 60Hz and 7000Hz are fed simultaneously to the input of the amplifier under test. Their interaction with each other is measured at the output of the amplifier, as the test is performed at different output levels.

The IM test results are then graphed on a voltage or power scale: voltage output for preamps, and wattage output for power amps. Since harmonic distortion is given as a function of frequency, and intermodulation distortion as a function of output level, there is no direct comparison between the two. Usually, however, in audio equipment of good design, the IM readings are several times higher than the harmonic distortion readings.

(20Hz-20KHz, inputs shorted)
Hi-Level inputs: 90db below rated output of 2.5 volts.
(typically lOOdb below rated output with IHF "A" weighted measurement)
Phono inputs: 80db below 10mV input (less than luV) (typically 0.5uv)

Hum and noise designate an unwanted collection of spurious signals of different frequencies and amplitudes that lurk somewhere around the lowest output levels of your audio system. The chart below indicates the range between the noise levels and the operating levels of the IC-150. The dynamic range of audio equipment indicates the usable range of output - in other words, the range that lies between noise interference at low levels and distortion or overloading at high levels.

The dynamic range of an audio production indicates the difference in volume between its softest and loudest parts. A dynamic range of 60db, for instance, means that the highest signal levels are 60db (1000 times) higher than the lowest signal levels.

Noise becomes the limiting factor for most audio media. A very good tape or record may have a range of about 70db, while a tuner can carry programming with about a 60db range. Trying to expand the range further brings noise into the low levels of the programming.

The human ear can safely appreciate a range of about lOOdb, but any dreams of approaching that range with listening material will remain dreams until the problems of noise and distortion have been further subdued. The relative level chart indicates where the average program range might fall in the operation of an IC-150 preamp.

At the levels shown, the softest sounds being played stay well above the noise level. By lowering the volume too far, however, with either the phono gain pots or the main volume control, the program can be turned down far enough to get into the noise region at the low end.

The problem of noise can be compounded by the unfortunate truth that power amplifiers will indiscriminately amplify noise along with everything else. If the final amplifier stage of your audio system adds 30db of gain to the signal, it also increases the noise in the signal by 30db, which may bring the noise up to an annoyingly audible level.

To make the best of this situation, it is a good idea to keep your power amp below full gain, and provide as much of the level as possible with the preamp. The diagram below illustrates the point here. By increasing the preamp gain, we get more output signal without more output noise. This makes it practical to set the gain of the power amp at a lower level, and thus to amplify the noise much less.

The result is the same signal level at the output, with a lower noise level. Care must be taken however, to keep the amplifier gain high enough to allow full output from the amplifier before the IC-150 overloads at 10V of output.

The square wave response of any audio equipment indicates the bandwidth of the equipment. High frequency square wave response shows the ability of the equipment to respond quickly to sudden changes in the signal (or to accurately reproduce high frequency signals).

The low frequency square wave gives an indication of the degree to which the input coupling circuit (which blocks dc) affects low frequency signals. Square waves work particularly well for demonstrating circuit response speed, because in accurately reproducing the waveform the circuit must switch suddenly back and forth between different levels, while maintaining stability, which is a hard thing to do.

The square wave makes a simple visual test because any distortion in this simple waveform is comparatively easy to see. The square wave response of the IC-150, as shown above for both low and high frequencies, demonstrates the capacity of this unit for clearly amplifying a wide range of frequencies. Another description of response speed is the slewing rate figure, which tells how quickly the preamp can change output levels. The rate of change is expressed as volts per microsecond, meaning that the output level can change so many volts in one millionth of a second. For the IC-150 the slewing rate typically measures 4.25 volts/microsecond.

Crosstalk designates any interference of one input with another. For instance, if you leave your tuner turned on while you switch to a phono input to listen to a record, it's super-annoying to hear the tuner output combining with your phono output. In the same way the inputs to the tape and auxiliary terminals are not supposed to combine their efforts, but are to remain separate so that the selector switch can indeed give you a real choice.

Several conditions affect the problem of crosstalk. The output impedance of your source (such as a tuner or tape deck) is a factor, with a high impedance output making the problem worse. Frequency is also a factor. As frequency increases, crosstalk generally worsens, although standard procedure is to give crosstalk figures (when they are given at all), only at lKHz.

Inside the preamp, wire dressage is a factor in keeping crosstalk low. Essentially, wires from inputs to switch terminals and then to the amplifying circuitry must be efficiently separated to prevent the signal on one wire from feeding into any other wire. The most conservative way to rate crosstalk is to check all combinations of inputs and pick the worst case as the rating.

For the IC-150, the worst crosstalk at lKHz (with a 50 ohm generator at 2.45V out and the undriven input terminated with a 5K "source" resistor) is Tape 2 feeding into Tape 1 with the selector on Tape 1. The difference in levels is better than 66db, which means that the unwanted signal is typically more than 2000 times smaller than the desired signal. The crosstalk between the other inputs is generally better, with the Phono inputs, for instance, showing crosstalk down by more than 95db between them at lKHz.

In general the readings are degraded directly by the magnitude of the "source" resistor. That is to say, for a more typical source impedance of 500 ohms the worst case crosstalk would be 86db, a tenfold improvement.

Separation is the bedfellow of crosstalk, as it designates the degree to which either of the two stereo channels interferes with the other. Again, increasing frequency makes the problem worse. The same method of measurement is followed as was used to rate crosstalk (i.e. find the worst case and use it as the rating).

Typically the worst separation in the IC-150 occurs with the left channel feeding into the right channel on the Tape 1 input. The separation is generally worse with the volume control low - with the worst case being about 55db separation at lKHz (the unwanted signal more than 500 times smaller than the desired signal) when the volume is turned almost all the way down. With the volume control at maximum the separation is typically 65db (a difference in signal levels of better than 1500; this becomes 85db with a 500 ohm source impedance). The separation when other inputs are used is higher, with the Phono inputs, for instance, showing separation of 80db at lKHz (a difference of 10,000 in signal levels).

The IC-150 provides the important basic control center functions in a unit designed for clean sound and uncomplicated operation. Especially noteworthy qualities include the uniquely low distortion and noise levels, and the exceptionally good frequency and phase response. These qualities combine with simple and precise mechanical operation to afford versatile handling of programs from all audio sources.

The electronics of the IC-150 are built around two integrated circuits which provide the equivalent of 22 transistors and 14 diodes. Beside these there are 13 bipolar transistors, 1 FET, 2 zeners, and 8 diodes.

• Anmerkung : Diese so oft (auch bei anderen Herstellern) herausgestellte Aussage, wieviele Transistoren und Dioden ein Gerät hat, war damals wie Heute absolut unbedeutend und hatte wirklich nicht den geringsten Einfluß auf den Klang.

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The IC-150 requires about 2 watts for its operation. The power supply can be wired for 120 or 240 volts, and will operate on any frequency from 50Hz-400Hz.

On the back of the unit are provided 5 ac outlets for supplying equipment used with the preamp. Four of these are powered by the on-off switch of the IC-150, while the fifth is wired directly to the power cord before the switch. The unswitched outlet powers your turntable, to avoid turn off in mid-cycle with possible damage.

The output from the IC-150 to the following amplifier is automatically muted for several seconds to protect speakers. When the IC-150 is turned on, a relay keeps the output off long enough to allow normal turn-on transients in other equipment to die down, thus preventing these transients from harming speakers. About 5 seconds after the ac switch is pressed, the muting relay closes to allow normal operation.

A conceptual layout of the operation of the IC-150 appears in the signal flow diagram. For any who want more detail the actual electronic components are shown on the schematic following. The signal flow diagram shows the sequence of operations upon an audio signal as it passes from input to output (moving from left to right on the diagram).

At the extreme left of the chart the selection of inputs appears, all of which feed to the rotary selector switch. If the phono inputs are used, the signal goes through the selector switch to the phono preamp and employs a low-distortion, low-noise cascode design. Other features of the phono preamp include the equalization circuitry (to afford precise matching of the RIAA response curve) and the phono level controls. Following the phono preamp the signal is returned to the selector switch.

From the selector switch, the signal (either from the phono preamp or from tape, aux, or tuner inputs) goes to the tape outputs and the tape monitor circuitry. The tape outputs route the signal to your recorder(s), while the pushbutton activated tape monitors provide a means of listening to whatever is coming into the Tape 1 and Tape 2 inputs when the selector switch is set on a different input (you may monitor the tape you are making, comparing the tape with the source you are taping). The next part of the circuit is the low filter, which is normally bypassed. It can be added to the circuit by depressing the low filter button.

Following the low filter come the volume control and loudness circuitry. Depressing the loudness button adds the loudness compensation circuitry to the signal path. When the volume control is turned to maximum, the loudness compensation has no effect. As the volume control is turned down, the compensation prevents the bass and treble tones from attenuating as quickly as the mid range tones. This provides the boost necessary to keep the loudness levels balanced. When the loudness button is out, the loudness circuitry does not affect the signal at all.

The next controls affect the stereo image of your music. The first of these, the balance control, works by attenuating one channel while maintaining the level of the other. At the extreme positions of the knob, one channel is at the level set by the volume control while the other is completely off. In between, the relative volume levels of the two channels may be set in any combination which suits the surroundings of a particular system. At any setting, complete separation is maintained between the two channels.

The pan control allows you to mix the signals of the two channels in any combination from normal stereo to reverse stereo. In the "Normal" position, the left and right channels appear normally, with complete separation. As the control is turned away from normal, the two channels begin to mix, until at the "Mono" position, the channels are completely mixed and there is no difference between the right and left outputs. Continuing to turn the control increases separation again, but so that the original left channel begins to appear at the right channel output, and the original right channel appears at the left.

At the "Reverse" position the two channels have been completely separated in the reverse position. The control thus offers complete freedom to mix the channels to the degree that suits your personal musical tastes.

Immediately following the pan control is the main amplifier section of the IC-150. Employing a quiet, low-distortion integrated circuit in an operational amplifier configuration, the circuit amplifies signal voltage by 20.8db.

The bass and treble controls appear in the feedback circuitry of the main amplifier. These are designed to provide a wide dynamic range, and allow control of the 20Hz and 20KHz frequencies in excess of ±15db.

By depressing the "push-for-flat" button, the tone controls can be completely cancelled, and a flat frequency response obtained regardless of the tone control settings.

The final section of circuitry which helps shape the signal is the high filter. As with the low filter, it is normally bypassed, and only affects the signal when the high filter button is pushed.

The last active circuitry before the output terminals is the muting circuit. When power is initially applied to the IC-150, the muting relay contacts tie the output to ground. The muting relay remains in a relaxed state until an RC circuit charges and turns on an FET, which in turn energizes the relay and removes the short from the output. This process absorbs approximately 5 seconds, time during which turn-on transients can die out before the speakers are connected to the circuit.

The power supply includes 3 separate dc supplies to operate the IC-150. Regulated positive and negative 18 volt supplies go to the operational amplifier and the phono preamp. Besides these, a third low-energy supply is provided for the muting circuit.

If the leatherette case of the IC-150 is scratched, the scratches can be removed with scouring powder, followed by washing with a dishwashing liquid and water. Furniture polish can be used to shine the cover.

220 VOLT CONVERSION
Converting the IC-150 power supply from 120 volts to 220 volts can be simply accomplished with a soldering iron and a pair of wire cutters. The accompanying diagram shows the wiring involved in the following sequence of operations:
1) Remove the bottom cover of the IC-150 (held on by 9 screws).
2) With the unit upside down, and the front panel toward you, locate the terminal strip on the bottom in the near left-hand corner.
3) Cut the jumper wires running between the white/orange and blue/yellow conductors, and between the black and green/black conductors.
4) Connect the blue/yellow and green/black conductors together by soldering a jumper wire to their terminals.
5) Replace the 1/8 amp line fuse with a 1/16 amp type 3AG fuse.
6) Change the line cord tag to read 220 volts.

PROBLEM POSSIBLE CAUSES OR CURES

High noise or hum
Power amp turned wide open - adjust amp according to the owner's manual.
Poor connection in associated wiring. - Ground loop between IC-150 and associated equipment. - Open ended input (i.e. shorting plugs removed without having put any input from tuner, phono, etc.)
High noise or hum in phono

Above suggestions apply. - Gain pots on phono board have been turned up.
Turntable not grounded to ground lug of IC-150. - Turntable not properly wired causing clicks, hum, noise, etc. - High local RF radiation from TV or radio stations - keep leads short, well dressed.

Scratchy volume or other controls; also pops in switches
Output caps in tuner, tape deck, etc., leaky causing D.C. to appear on volume control, LO filter, loudness button, and Bal & Pan controls. This will also cause pops in the selector switch.

One channel dead
Balance control not set to normal. - Broken or shorted cables either coming into or out of IC-150 (try reversing the leads). - One or more switches not properly released or depressed. (Try depressing and releasing all switches.)

Both channels inoperative
Suggestions for "One channel dead" apply. - Muter terminals not tightened down. - No wire in muter terminals. - External (remote) muter switch not turning on - e.g.: turntable muter inoperative may make it impossible to get any signal through the IC-150. - One or both tape monitor switches engaged. - Fuse blown. - IC-150 or associated equipment not plugged in, turned on, or turned up. - Shorting plugs in outputs either "main" or "tape." - No input signal or shorting plugs in the input.

Distortion at high listening levels
Possible vibration from speakers being picked up by phono tone arm and amplified by the IC-150.

High Frequency Oscillation (Power amplifier mysteriously heats)
Power Amplifier output is being fed back to IC-150 inputs via poor lead dress, AC mains from electrostatic speakers, etc.

Low Frequency Oscillation
Mechanical feedback between loudspeaker and turntable.
Poor AC line voltage regulation causing power amplifier to feedback to unregulated equipment being used as signal source or speaker equalizer ahead of IC-150.