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But don't let power alone determine your choice of receiver or amplifier - By STEVEN RAUTENBERG - Off Duty / Europe / November 1974

OFF DUTY SHOPPERS are a service to our readers and are prepared by the editorial department based on information supplied by representatives of the manufacturer. They are not intended as advertising nor as an endorsement of any particular products. Prices given in the SHOPPERS should be used only as a guide. They are not binding on any retailer and may vary somewhat depending on the retailer, location or general monetary situation.
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IN AN AGE of 55 miles per hour speed limits, 68 degree winter thermostat settings and darkened public buildings, it's nice to know there is still somewhere you can have more power and, if not speed, plenty of volume.

Today's receivers and amplifiers provide more watts per channel than ever before and nowhere is the change more dramatic than in 4-channelunits.Atthe debut of 4-channel receivers and amplifiers a few years ago the average rms power rating was seldom more than eight watts per channel.

This power output was sufficient for small rooms using high-efficiency speakers but it soon became apparent that audiophiles wanted, and were willing to pay for, enough power to drive four of the least efficient accoustic suspension speakers at undistorted, ear shattering volumes.

Today 4-channel receivers offer 50 watts rms (sorry, 40 Watt rms was true) or more per channel, enough power for any set of speakers in virtually any room. With strappable outputs such a receiver or amplifier will provide a thunderous 120 watts per channel in the stereo mode.

The quest for power is not limited to 4-channel units however. Stereo amplifiers and receivers offer 110 watts rms or more per channel, power ratings that once were obtainable only with professional-style separate power amplifiers.

A high power amplifier, of course, is not for everyone. Not all audio enthusiasts wish to share their favorite sounds with the folks on the other end of town.

Furthermore, a high-power amplifier is subject to "crossover" distortion which becomes audible at very low output levels, so if you plan on using high efficiency speakers, it is best to use them with a middle or low power amplifier.

You'll save money too. If, however you have chosen any of the increasingly popular low-efficiency speakers for use in a large room or at high volumes, a healthy power output is a must for undistorted, full-frequency response.

Either way, don't let power alone determine your choice of receiver or amplifier. Use this shopper to examine the other specifications and features. Then, when you get home and plug it all in - try not to blow any fuses.

Each manufacturer has some unique features and this is one of the interesting parts of comparing various units. How many sets of speakers do you want to operate? Do you want remote control? How many tape decks do you want to connect?

The questions and options seem endless. These are the features, though, that allow you to build into your system the versatility and individuality you want. And with the wide range of units available, that means you can have just about anything. Here are just a few special features you may wish to consider when shopping for a receiver, tuner or amplifier.

A Dolby noise reduction circuit built-in to your receiver or tuner has a number of advantages. You do not have to pay for an extra chassis and power supply as with separate Dolby units. Then there is the convenience and versatility of having the Dolby circuitry fully integrated with the other preampfunctions and circuits.

A Federal Communications Commission ruling this past June 1973 has paved the way for Dolby FM broadcasts, and since then over one hundred Stateside FM stations are broadcasting Dolbyized signals.

To optimize the effectiveness of Dolby broadcasts, the pre-emphasis of the signal and de-emphasis of the tuner are lowered to 25 microseconds.

Pre-emphasis the amount by which high frequencies are boosted during transmission. Most receivers and tuners with Dolby systems therefore have a variable de-emphasis - 75 microseconds for standard American broadcasts and 25 microseconds for Dolbyized signals.

Some units will also have a 50 microsecond de-emphasis which is the European broadcast standard.

If your tuner does not have the 50 microsecond de-emphasis you can still receive European FM broadcasts with only a slight variation in the upper-range tones which can usually be adjusted with a standard treble tone control.
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An equalizer is really an elaborate tone control which divides the frequency range into five or more bands, either to compensate for room accoustics or tailor the music to your individual taste. Boost a mid-range vocal you like, or mute that insipid string section which was dubbed in the studio over a live recording.
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Some components have electronic overload protection circuits which, unlike standard fusing will re-set automatically, restoring power to the unit after the offending signal is remedied and a few seconds of recovery time have elapsed. This way a momentary power surge will not require a change of fuses.
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European made components have traditionally used DIN plugs instead of standard phono jacks. To use two components in conjunction with each other that were designed for two different systems requires not only a mechanical adaptor but, in addition, a compensation for differences in output levels. Many new receivers, tuners and amps are now equipped with outputs for both types of cables.
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What do all the strange letters stand for? You may read that an amplifier is an SEPP-ITL-ICL-OTL-OCL- type (single-ended, push-pull, input-transformerless, input-capacitorless, output-transformerless, output-capacitorless) but what does it mean to you? Relatively little. For the industry in general it means that units are now being manufactured to higher standards with fewer components and thus, less expensively.

You save money. The reduction in reactive components (capacitors and transformers) will change the phase characteristics of an amplifier but this is something you won't notice-your amplifier probably already exceeds the capabilities of your speaker system.

While quadraphonicsound will see a lot of future change, it has firmed up a great deal in the last year (und verursachte überall jede Menge an Frust). Here are some of the things you will note when looking through the units available.
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For simplicity, we have labeled two types of matrix decoders, Regular and SQ.

There are definite differences between the two and you should really have the same type decoder as the material you are trying to decode. There are also a few "universal" decoders which claim to decode any type of material.

Some units may have one type or the other decoder with connections for add-on adapters and some may also have decoder with logic circuitry to enhance separation. A full logic matrixdecoder can enhance 4-channel separation to a degree that favorably compares with CD-4 discrete systems.

Partial logic circuits offer enhanced separation too, but at a measurably lower decibel rating. Both forms of logic circuitry can be found on 4-channel receivers and amplifiers currently on the market, or they can be purchased separately with a variety of matrix decoders. With the various adapters available today, you can easily add any type decoder system you want with no difficulty.
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JVC's CD-4 system - which uses a carrier - has been included in several units along with built-in matrix decoders. Other manufacturers have provided pockets in the side or bottom of their units which accept a plug-in CD-4 module, while still other units have external connectors for add-on demodulators. As is the case with matrix systems, CD-4 can be added to almost any system without difficulty.
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These are the 4-channel matrix decoders that are tacked on the output of a stereo amplifier and produce 4-channels at high power levels. Therefore, you will see several units in this section which have only two amplifier channels yet claim to produce genuine 4-channel sound.

Be careful, though, to see that the unit you are considering actually has the decoder and is not offering simply four speakers connected in two stereo pairs. Remember, too, that stereo amplifiers with high-level decoders cannot handle discrete 4-channel material as can units with 4-channel amplifiers.

Most of the 4-channel units in our listings have four separate amplifier channels and are marked as such. This means that they can handle either discrete 4-channel material or decoded matrix material.
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Several units in our listings have circuits which can enhance stereo material by feeding portions of the material to the rear speakers thereby giving a 4-channel effect. This may be accomplished with a delay circuit, by separating out-of-phase signals for the rear channels or by frequency differentiation. In any case, remember that this is not matrix nor discrete 4-channel, but simulated 4-channel.
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While it may be a few years before 4-channel FM broadcasts become a common reality, some manufacturers are preparing for that day by including outputs for decoders and signal indicators on theirtuners and receivers. In the meantime several stations in the U.S. are broadcasting matrix 4-channel material which can be decoded with the matrix decoders already built-in to many units.
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The most complete specifications for amplifier outputs show the RMS power when the amplifier is driven into an 8 ohm load with all channels operating without exceeding a given amount of distortion at any or all audio frequencies.

Some amplifiers will be rated with only one channel operating which generally means that they can produce more power, as is the case when the amplifier is rated only at a midrange frequency.

A full-frequency, full-operation specification might read, "RMS power output 33 watts per channel into 8 ohms 20-20kHz. with 0.5 per cent harmonic distortion, both (or all) channels operating."

This description covers just about all the variables (with the exception of line voltage) and is an excellent start toward choosing an amplifier. You will note that many units omit one or more of the factors in the preceding description and, while this does not mean that the unit is inferior, you might want to take a more conservative view of the easier, they will provide a sound experience.
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A good amplifier covers the audio spectrum with a minimum of variation. In other words, at a given amount of power it should amplify all frequencies equally - within one or two decibels (±1dB).

Frequency response is usually measured at normal listening levels, which under average conditions is about one or two watts. At higher power levels, a really "flat" response is more difficult to achieve and such an amplifier is likely to cost more. Here again is where the full-frequency power rating is important.
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This measure follows standards set up by the "Institute of High Fidelity" (IHF). It represents the range of frequencies over which the amplifier can deliver at least 50 per cent of its rated power.

"Half power," incidentally, is a reduction of just 3dB with sharp peaks at some frequencies and dips in the response curve at another frequencies. So the amplifier's power bandwidth of, say, 20-30,000 Hz, and its low-level frequency response curve (ideally, within 2dB throughout the audible range) are tell-tale indicators as to its performance.
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The distortion figures tell whether an amplifier does anything to the signal other than amplify it. Usually, both harmonic distortion and intermodulation (IM) distortion are given. Figures lower than one per cent are considered acceptable.

For a truly meaningful rating, look for harmonic distortion measurements at more than one frequency. Like the power rating, the spec is likely to be more impressive at a mid-frequency than at the extremes of the audio spectrum.
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All amplifiers add signals of their own to your input signal. You can hear this by turning up the volume control on your amplifier without putting any signal into it. The hum and noise specification tells you how much extraneous sound the amplifier produces in relation to the output signal. Look for a rating of at least -60 dB and an even better -70 dB rating if you plan to do a lot of tape recording. Make sure that the rating is taken through the phono input and therefore includes the preamp (where most of the noise is added).
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Die Tuner-Beschreibungen sind nicht mehr relevant und darum werden die hier übergangen.
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With the more complete specifications it is easier than ever to see what your money is buying. One thing, however, which you can't tell unless you're a trained technician is the amount of longevity built into a unit through careful design and high quality.

About all you can do is rely on the manufacturer's reputation, the advice of a trusted technician and, perhaps, independent test reports. In most cases, you'll find that those units recommended for long-term quality are also the more expensive units - so, you're trading dollars for longevity.

The dilemma is yours to solve and while the hundreds of units in this SHOPPER may not make the choice any easier, it will be a sound experience.
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