By JULIAN D. HIRSCH /Hirsch-Houck Laboratories
Results of our laboratory measurements on seventeen of the newest hi-fi models. Recent design trends are covered, along with descriptions of other available receivers.
THE latest stereo receivers reflect, for the most part, their designers' utilization of recent developments in semiconductor devices and assembly techniques. As always, styling is an important consideration for a component occupying such a visible position in the user's home, and here each manufacturer has gone his own way. As might be expected, certain design trends (push-button switches, slider-type controls, etc.) appear quite generally throughout the field.
For this survey, we have tested seventeen stereo receivers from as many manufacturers. Most manufacturers offer a line of receivers, similar in general configuration, but with substantial differences in power output, sensitivity, and price. In such cases, we will describe the other models briefly, indicating their principal differences from the unit tested.
The receiver tests were generally similar to those we perform for our regular equipment reports, but were slightly abbreviated to simplify a tabular presentation of the data. Unlike some equipment "surveys" which present only the manufacturers' specifications, all the performance data in this report was obtained from actual measurements made in our laboratory.
Due to normal variations from unit to unit and to differences in test conditions, our numerical data may not always match the published ratings, but since it was obtained under identical conditions for all the receivers, it forms the basis for a valid comparison.
Recent Design Trends
Certain features are common to most of the receivers, and need only be mentioned where a particular model differs from the others. For example, AM reception is provided by all the units except the AR, which is an FM-only receiver. Although some of the AM tuners contain interesting design features, and there are significant differences in performance among them, we did not test them except for a brief listening evaluation. In our judgment, all of the units in this survey offered satisfactory AM performance, although none could qualify as a "high-fidelity" AM receiver.
The KLH 27 was the only receiver lacking a front-panel stereo-headphone jack, capable of driving low-impedance phones. All the receivers had tape-recorder inputs and outputs, with switches for monitoring from a three-head recorder while recording. A few, as noted in the table, had additional tape-input and output jacks on the front panel for connecting a recorder without access to the rear of the receiver, or for dubbing from one recorder to another.
As far as we could determine, all the receivers tested had FET r.f. amplifiers, and many also used FET's in the mixer stage. In a few cases (Harman-Kardon, Panasonic, and Sherwood), schematic diagrams were lacking, but we assume from their performance and the current state of the art that they also used FET's. The FET is relatively immune to overload and cross-modulation effects from strong signals.
With their freedom from self-heating, solid-state receivers are virtually drift-free, and automatic frequency control (a.f.c.) is rarely used nowadays. The only receiver in this group to use a.f.c. was the Fisher 450-T, not to correct any drift problem, but because its signal-seeking "Autoscan" tuning requires a.f.c. to lock on to a signal once it is acquired.
A few years ago, the Heath AR-15 initiated a trend toward permanently tuned i.f. filters. (This feature was also found in the Marantz 10B FM tuner.) These filters can be designed to have a flat-topped, steep-skirted pass-band response, much closer to the ideal shape than is readily obtainable with conventional double-tuned i.f. transformers.
Their controlled phase-shift characteristic is also highly desirable for uniform stereo-channel separation across the audio frequency range. The elimination of periodic realignment is an obvious benefit to the consumer.
The Heath AR-15 uses a relatively costly quartz-crystal filter. Since its introduction, many other receiver designs have incorporated fixed i.f. filters of various types. Some use quartz crystals but there is a trend toward the much less expensive ceramic filters. From a practical standpoint, a well-designed ceramic filter seems to perform as effectively as a crystal filter. Still another approach is found in the new Heath AR-29, which uses a hermetically sealed, multi-pole LC filter. The top model of the Sherwood line (the SEL-200, not tested for this report) also uses an LC filter in its i.f. section.
Integrated-circuit (IC) i.f. amplifiers are used in most of today's receivers. Their high gain and excellent limiting properties contribute to their popularity among receiver designers. As far as we could determine, only the KLH 27, which has been on the market for several years, still depends entirely on discrete components and transistors in its i.f. amplifier.
Integrated circuits have made slower inroads into other portions of stereo receivers, but there are clear signs of a change in this situation. The Motorola multiplex IC, which replaces most of the usual multiplex demodulator components and does a generally superior job in addition, is now used by Electro-Voice, Heath, Marantz, Pioneer, and Scott.
Scott also uses an IC in its audio preamplifier stage. It seems probable that there will be greater utilization of IC technology in future receiver designs (such as the recently announced IC's which combine i.f. amplification, limiting, FM detection, and audio amplification on a single silicon chip). Several types of tuning aids are found among these receivers. Some use a single meter indicating relative signal strength, and are tuned for a maximum meter reading.
When used carefully, this can be an adequate tuning indicator. A more accurate method is the zero-center meter used by other manufacturers. Some receivers provide both types of metering with the relative signal-strength indicator being most useful for aiming a rotatable directional antenna.
An interesting variation on the zero-center tuning meter is the voltage comparator used in the Scott and Lafayette receivers. This is a circuit which monitors the d.c. output from the discriminator and extinguishes a lamp on the front of the receiver when the voltage departs from zero (the condition for correct tuning). The circuit is inhibited from functioning unless a signal is actually being received. When the lamp is lit, it illuminates a suitable word on the dial ( "Perfectune" and "Acritune" for the Scott and Lafayette models, respectively). This indicator can be made extremely sensitive to mistuning and eliminates all user judgment in tuning the receiver. Scott uses an IC voltage comparator; Lafayette uses discrete circuits with several transistors.
The Fisher "Autoscan," which we mentioned earlier, causes the receiver tuning to sweep electronically across the FM band until a signal is received and the a.f.c. locks it in. The scan can be initiated by a push-button on the panel or with a remote-control accessory.
One trend which we are pleased to note is the use of linear dial calibration. Instead of a one-megahertz band segment occupying a quarter-inch at one end of the dial and an inch at the other end, a linear-tuning receiver maintains a uniform tuning rate throughout. If a sufficient number of intermediate calibration points are provided, it is possible to interpolate dial readings and set the receiver accurately to a desired frequency, or to identify a station unambiguously from its position on the dial. Linear dial scales are found on the AR, Sansui, and Sony receivers.
Almost all receivers have outputs for two pairs of speakers with switches to energize either or both sets. Exceptions are AR, which has only a single set of outputs, and Pioneer, which has three sets.
A few of these receivers have unconventional features which are deserving of mention. Bogen incorporates a "Crescendo" compressor /expander circuit. This can be set to expand the dynamic range of music which was previously compressed (this applies to all recorded music) or to restrict the dynamic range when the program is used for background purposes and occasional high-level passages might be annoying. The circuit works well, without objectionable distortion or other side effects. Marantz has a unique antenna-tuning feature which connects one of its tuning meters to display the amplitude fluctuations caused by multipath distortion. (This is done by a much more expensive cathode-ray tube on a higher-priced Marantz model.) In use, the antenna is rotated for minimum meter fluctuation which corresponds to minimum multipath distortion. Pioneer has a front-panel gain control and internal mixing circuits for a microphone which is supplied with the receiver. This allows the receiver to be used for public-address and similar applications.
On some receivers, the preamplifier outputs and power amplifier inputs are brought to jacks in the rear, with a switch or external jumper cables to join them for normal operation. By separating the two sections of the amplifier, an electronic crossover network, active equalizer, reverberation unit, or similar accessory can be used in the system without disturbing the tape-monitoring function which is sometimes appropriated for this purpose. This feature was offered on the Altec, Kenwood, Pioneer, and Sansui receivers in the group tested.
Test Procedures
With both channels driven simultaneously into 8-ohm loads, the power output per channel was measured at the point where the harmonic distortion reached 2 %. This was done at 30 Hz, 1 kHz, and 20 kHz. At 1 kHz, the total harmonic distortion was measured at 1 watt, 10 watts, and "Max Power," which was actually 1 dB or about 20% less than the 2% distortion power output. These measurements give a concise picture of the audio performance of the receiver over a wide range of frequencies and power outputs.
As a guide to users having 4-ohm or 16-ohm speakers, the maximum output into these impedances was measured and expressed as a percentage of the available output into 8 ohms.
The audio sensitivity was measured at maximum volume-control settings, through both Aux and Phono inputs, at 1 kHz. It was considered to be the number of millivolts input needed to develop a 10-watt output. In addition, the phono overload point was measured by reducing the receiver volume-control setting and increasing the input signal level until the output waveform began to distort (at low-power levels). This was expressed in decibels relative to the phono sensitivity for 10-watt output. The phono dynamic range reserve of the tested receivers ranged from 26 dB to over 40 dB with the average being about 32 dB. Receivers falling near the low end of this range should be used with fairly low-output phono cartridges to avoid the possibility of overload and distortion on loud passages. Those measuring about 35 dB or more are not likely to be overloaded by any current phono cartridge or record.
The unweighted audio signal-to-noise ratio was measured with the gain set to standardized values (1 volt input on Aux, or 10 millivolts on Phono, for 10-watt output at 1 kHz). It is expressed in decibels relative to 10 watts. The accuracy of the RIAA phono equalization was measured and expressed in ±dB relative to the 1-kHz response between 50 Hz and 15 kHz. We also measured the tone-control curves, loudness-compensation curves, and filter responses, but these do not lend themselves to a tabular format. All the receivers except the AR had switchable loudness compensation, and all had satisfactory tone controls. The AR tone controls had characteristics which made them suitable for very effective loudness compensation.
The IHF usable sensitivity was measured for each FM tuner section at 100 MHz. The FM distortion, with a 75-kHz deviation, was measured at 1000-microvolt input level.
We also reduced the signal input until distortion was 3 dB greater than the latter value. This was considered to be the weakest signal which could be received in mono with entertainment quality. The ratio of this figure to the IHF sensitivity is an indication of the steepness of the tuner's limiting curve; the lower the numerical ratio, the better the limiting action.
The FM tuner frequency response was measured between 30 Hz and 15 kHz and expressed in ±dB relative to the 400-Hz level. Stereo channel separation was measured at 50 Hz, 400 Hz, and 10 kHz.
Other receiver features are indicated in the tabular listing. Note that a Lo Level center-channel output is typically about 1 volt, to drive a separate power amplifier and speaker directly. Unless otherwise specified, dimensions and weights are our own measurements, from the rearmost protrusion (usually the AM ferrite-rod antenna) to the maximum front-panel knob extension, and including the supporting feet in the height measurement.
It will be evident from a study of the table that all of the receivers in this group are of excellent quality and some of them are truly outstanding.
Their wide price range, from $200 to $450, is reflected in their audio power outputs and distortion, FM sensitivity, and in the general flexibility and convenience offered. All of the receivers come, at the least, with a complete metal enclosure. Some have wood-grain finished metal cabinets, and a few include a wooden cabinet as standard equipment.
Accessory wooden cabinets are available for virtually all models.
Obviously, one's choice should be influenced by the other system components. Low-efficiency speakers require considerable amplifier power; some of the lower-powered units, otherwise excellent, might not be suitable for use with them. In most urban and suburban locations, any of the receivers has more than sufficient FM sensitivity. In fringe areas, the more sensitive models would be indicated.
Other factors such as possible use of one or more tape recorders or more than one record player will influence one's choice.
A major consideration, in many cases, is the styling of the receiver. This, of course, is a totally subjective matter. The units reviewed for this survey vary from starkly functional to verging on gaudiness-take your choice! In any event, all of them performed very well indeed, and we would be happy with any of them from the standpoint of performance and listening quality.
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OTHER STEREO RECEIVERS
BECAUSE of time and space limitations, we were able to test only one receiver from each of the manufacturers listed in the table above. In addition to the models tested, most of these companies have other receivers in their lines. More expensive models usually have higher output power, an improved tuner section, and more features. Also, some manufacturers make the tuner or amplifier sections of their receivers available as separate components. In all cases, prices have been rounded off to the nearest whole-dollar amount and these prices are all "audiophile net," which is the price the final buyer pays for the receiver. All prices are subject to change.
Acoustic Research also has available the Model AR stereo control amplifier with specs similar to the amplifier section of its receiver. The amplifier, rated at 50 W /ch (watts per channel) continuous power output into 8 ohms, is priced at $250, with metal cover.
Altec-Lansing also offers the Model 725A, an AM /stereo-FM receiver rated at 60 W /ch continuous power output into 8 ohms. The tuner section has slightly better sensitivity and capture ratio than the Model 714A. Price is $699 without cabinet.
Bogen, in addition to the Model BR360 tested, has a number of other AM /stereo-FM receivers with various output powers. The Model BR320 is rated at 15 W /ch cont. power output into 4 ohms and is priced at $200. The Model BR340 is similar except that its power output is 30 W /ch cont. into 4 ohms and is priced at $250. The Model BR350 has a built-in expander-compressor, and is rated at 30 W /ch cont. into 4 ohms; its price is $280. Finally, there is the Model BR-380, which is the same as the BR350 but with a power rating of 45 W /ch cont. into 4 ohms and a price of $350. Cabinets are optional at additional cost.
Electro-Voice also has a Model E-V 1181 stereo-FM receiver rated at 21 1/2 W /ch cont. power into 8 ohms and priced at $189. The Model E-V 1182 is similar but with an AM tuner added; its price is $210. Then there is the Model E-V 1281 stereo-FM receiver rated at 26 W /ch cont. power into 8 ohms and priced at $230. The Model E-V 1282 has AM added at a price of $249. The Model E-V 1382 is an AM /stereo-FM receiver with 40 W /ch cont. power into 8 ohms which is priced at $300. Separate walnut cases are available for all models. In addition to these receivers, the company also has Model EVR-1, an AM /stereo-FM receiver rated at 18 W /ch cont. power into 8 ohms and priced at $230 with wood cabinet. Also available is Model EVR-2, an AM /stereo-FM receiver rated at 27 W /ch cont. power into 8 ohms and priced at $300 with wood cabinet.
Fisher has a number of additional AM /stereo-FM receivers. The Model 201 is rated at 26 W /ch cont. power into 8 ohms and is priced at $200. The Model 202 is rated at 32 W /ch cont. power into 8 ohms and is priced at $250. The Model 210-T is rated at 36 W /ch cont. power into 8 ohms and is priced at $300. The Model 250-TX has a power rating of 38 W /ch cont. power into 8 ohms, features push-button tuning, and is priced at $350. The Model 500-TX is rated at 52 W /ch cont. power into 8 ohms, it has push-button and signal-searching tuning, and is priced at $500. The company also has a Model 701 four-channel receiver with an output power of 32 W /ch cont. into 8 ohms at a price of $700. Cabinets are separately available in all cases Harman-Kardon also has available the following AM /stereo-FM receivers. The Model 130 is rated at 10 W /ch dynamic power into 4 ohms at a price of $130 with walnut cabinet. The Model 230 is rated at 17'/2 W /ch dynamic power into 4 ohms at a price of $160, with cabinet separate. The stereo-FM Model 820 has a power rating of 55 W /ch dynamic power into 4 ohms at $270, with cabinet separate.
Heath also has a Model AR-14 stereo-FM receiver with a power rating of 10 W /ch cont. power into 8 ohms at a kit price of $120 less cabinet. The Model AR-15 is an AM /stereo-FM receiver rated at 50 W /ch cont. power into 8 ohms at a kit price of $350 and a wired price of $540, less cabinet.
The Model AR-17 stereo-FM receiver is rated at 5 W /ch cont. power into 8 ohms at a kit price of $73, less cabinet. The Model AR-19 is an AM / stereo-FM receiver rated at 20 W /ch cont. power into 8 ohms at a kit price of $225, less cabinet.
Kenwood has the following additional AM /stereo-FM receivers. Model KR-2120 is rated at 11 W /ch cont. power into 8 ohms at a price of $160, less cabinet. The Model KR-3130 is rated at 19 W /ch cont. power into 8 ohms at a price of $200, less cabinet. The Model KR-5150 is rated at 40 W /ch cont. power into 8 ohms at a price of $320, less cabinet. The Model KR-6160 is rated at 70 W /ch cont. power into 8 ohms at a price of $380, less cabinet. The Model KR-7070 is rated at 80 W /ch into 8 ohms, has automatic tuning, and is priced at $550. There is also the Model KR-4130 stereo-FM receiver rated at 24 W /ch cont. power into 8 ohms at a price of $220, without cabinet.
KLH has a Model 18 stereo-FM tuner with many of the same specs as the tuner section of the Model 27 receiver tested. The Model 18 is priced at $130, including cabinet.
Lafayette has a number of other AM /stereo-FM receivers in its line, all priced to include metal cases. The Model LR-75 is rated at 10 W /ch dynamic power into 4 ohms and is priced at $110. The Model LR-100 is rated at 20 W /ch dynamic power into 4 ohms and priced at $140. The Model LR-775 is rated at 40 W /ch dynamic power into 4 ohms and is priced at $200. The Model LR-1000TA is rated at 60 W /ch dynamic power into 4 ohms and priced at $240. Marantz also has available the Model 26 AM /stereo-FM receiver, which is rated at a power output of 10 W /ch cont. into 8 ohms at a price of $219, with metal cabinet. There is the Model 27, an AM /stereo-FM receiver rated at 30 W /ch cont. power into 8 ohms at a price of $319, with metal cabinet.
There is also the Model 19 stereo-FM receiver rated at 50 W /ch cont. power into 8 ohms at a price of $1000, less wooden cabinet. The Model 23 is a separate tuner with the same tuner section used in the Model 22 tested; price is $259, less wooden cabinet. The Model 24 is a separate tuner /preamp with the same tuner /preamp section used in the Model 22; its price is $339, less wooden cabinet.
Panasonic also has a Model SA-40 AM /stereo-FM receiver rated at 12 W /ch cont. power into 8 ohms and priced at $220. Model SA-60 is an AM / stereo-FM receiver rated at 22'/2 W /ch cont. power into 8 ohms and priced at $280. The Model SA-50 is the same as the SA-60 except without AM; its price is $250. There is also the Model SA-6500 AM /stereo-FM receiver rated at 50 W /ch cont. power into 8 ohms and priced at $400. The Model SA-4000 is a stereo-FM receiver with push-button and automatic tuning; power rating is 60 W /ch cont. power into 8 ohms; the price is $990. Pioneer has a number of additional AM /stereo-FM receivers in its line.
The Model SX-440 has 12 W /ch cont. power output into 8 ohms and is priced at $200, with cabinet. The Model SX-770 has 15 W /ch cont. power output into 8 ohms and is priced at $250, with cabinet. The Model SX-990 has a power output of 28 W /ch cont. into 8 ohms at a price of $300. The Model SX-9000 is rated at 50 W /ch cont. power output into 8 ohms and is priced at $500. The Model SX-2500 is rated at 84 W /ch cont. power into 8 ohms and is priced at $550. This model also features automatic signal-seeking tuning in the tuner section.
Sansui also has a rather extensive line of AM /stereo-FM receivers. Model 350 is rated at 18 W /ch cont. power output into 8 ohms at a price of $200. The Model 1000X has 34 W /ch cont. power output into 8 ohms at a price of $270, with wood cabinet. The Model 4000 has 45 W /ch cont. power output into 8 ohms at $350, less wood cabinet. The Model 5000A has an output of 55 W /ch cont. into 8 ohms and is priced at $400, less wood cabinet.
Scott also has a Model 631 AM /stereo-FM receiver which is rated at 18 W /ch cont. power into 8 ohms and priced at $200. The Model 342C is a stereo-FM receiver rated at 25 W /ch cont. power into 8 ohms and priced at $270. The Model 382C is the same, but with AM, at a price of $300. The Model 386 AM /stereo-FM receiver is rated at 35 W /ch cont. power into 8 ohms and is priced at $390. Sherwood also has, in addition to the receiver tested, a Model S-7500 AM /stereo-FM receiver with a rated output power of 40 W /ch cont. into 8 ohms, priced at $340 with a metal cabinet. The Model S-8500 is the same except without AM; it is priced at $300. There is also a Model S-7900 rated at 48 W /ch cont. into 8 ohms and priced at $440 with metal cabinet. The Model S-8900 is the same except without AM; price is $400. There is also the Model SEL-200 stereo-FM receiver rated at 42 1/2 W /ch cont. into 8 ohms priced at $599 with metal cabinet. Walnut cabinets are available at extra cost.
Sony also has a number of other AM /stereo-FM receivers available. The Model STR-222 is rated at 8 W /ch cont. power into 8 ohms and is priced at $150. There is the Model STR-6040 which is rated at 15 W /ch cont. power into 8 ohms and priced at $200. The Model STR-6065 is rated at 70 W /ch cont. power into 8 ohms and is priced at $400. Cabinets are available for all receivers at additional cost.
In addition to the models covered above, most of the manufacturers have a selection of other amplifiers, control amplifiers, and tuners to meet just about any user requirement.
-Milton S. Snitzer /Tech. Editor
Also see: Testing Hi-fi Equipment--Part 1--Test Equipment Required