MCS 3285 Stereo Receiver Review

The leader of the J.C. Penney MCS audio component series is the Model 3285, a digital-synthesis AM/FM stereo receiver rated to deliver up to 85 watts per channel into 8-ohm loads from 20 to 20,000 Hz with less than 0.005 per cent total harmonic distortion. Its front panel has no knobs or sliders. All functions are controlled by momentary-contact pushbuttons or large rectangular pushplates. The settings are indicated either by adjacent red LED’s or on one of the fluorescent display panels at the right of the controls.

The receiver’s dominant visual feature is its satin-silver-finished control panel, which occupies about 75 per cent of the front. There are a power switch, six program input selectors, and eight station-preset controls, each of which can be used for either an AM or an FM station. In addition, the entire group of presets can be switched to access a second bank of eight channels, for a total of sixteen AM or FM presets. The program sources include FM, AM, phono (for either an MC or MM cartridge), and two tape recorders.

Pressing the tune button causes the tuned frequency to change up or down, according to which end is pressed. Like many other digital-synthesis receivers, the Model 3285 can be set for auto scan (in either direction) when its tuning button is pressed momentarily; scanning stops only when a signal of sufficient strength is encountered.

Otherwise, the tuning advances by a single increment (0.2 MHz for FM, 10 kHz for AM) with each touch of the button or at a rapid rate while the button is held in.

The lower left portion of the control panel contains fourteen small buttons for such functions as the output connections (either main or remote speakers), audio filters (subsonic and high), an FM-multiplex filter, FM mute, i.f. bandwidth (wide or narrow), and stereo or mono mode selection. Other buttons mute the audio by 20 dB, select the MM or MC phono input, interconnect tape decks for dubbing from either one to the other, and change the scale of the fluorescent output-power display.

Another group of similar small buttons controls the various memory functions of the receiver. The tuning-processor buttons are used to enter a frequency into memory, to select memory banks Nos. 1-8 or 9-16, and to activate either the auto scan or preset scan mode. The latter mode causes the receiver to step through all the preset channels, playing each for 5 seconds and moving on unless the corresponding preset button is pressed. There is also an acoustic memory system in the Model 3285 that stores the settings of the filters and tone controls for subsequent recall at the touch of a button. There are two acoustic memory buttons, designated A and B, permitting instant recall of either of two sets of tone-control/filter settings. A defeat button disengages the filters and returns the tone controls to their flat settings.

Completing the front-panel controls are pushplates (like the tuning and input selectors) for the bass and treble tone controls, the balance control, and volume. Pressing one end of any of these controls causes its corresponding function to change up or down in small discrete steps similar to the detented steps of a typical knob-operated control.

The right quarter of the panel is devoted to the displays, which (together with the LED’s associated with the various controls) give a clear, unambiguous indication of the receiver’s operating status. At the top is a frequency readout using blue-white fluorescent numerals about 3/8 inch high. Five red lights show signal strength, and below them are an indicator for stereo FM broadcasts and one marked quartz locked, which shows that a station has been acquired and is tuned correctly.

In the center of the display group is the power-output readout, calibrated for each channel over a range of 0.02 to 150 watts into 8 ohms. The power-scale button multiplies these calibrations by 0.1 for increased display resolution at lower listening levels. At the bottom are the volume and tone readouts. The volume setting is shown both as a two-digit value of attenuation, reading in decibels from 0 (maximum volume) to 79 (the minimum audible volume setting), and as an illuminated bar graph. There is also a “volume-off” position in which the readout shows two half-size zeros.

The tone- and balance-control settings are shown as illuminated vertical (tone-con-trol) and horizontal (balance) bar graphs, each centered on a “flat” or "balanced" point. Each touch of one of these controls adds one more bar to its display; holding the pushplate in causes the function to increase or decrease in steps to its limit.

Except for the silver control panel, the exterior of the receiver is finished in very dark gray. The only front-panel feature other than the controls and indicators is a stereo headphone jack. The rear apron contains the usual input and output jacks, binding posts for connecting two pairs of speakers, and binding posts for FM and AM antennas (there is a hinged and pivoted AM ferrite-rod antenna). One of the two a.c. convenience outlets is switched.

The J.C. Penney Model 3285 is 19 inches wide, 15 inches deep, and 5-3/4 inches high, and it weighs about 30 pounds. Price: $599.95.

Laboratory Measurements

The Model 3285 is a rather large and heavy receiver, and its effective convection cooling—with air entering through the bottom grille, passing over the heat-sink fins, and exiting through the top-plate grille—kept the exterior at comfortable temperatures during our tests. Driving 8-ohm loads at 1,000 Hz, the amplifier outputs clipped at 100 watts per channel for a clipping headroom of 0.71 dB. The output into 4 ohms was almost the same, 98 watts per channel, and into 2-ohm loads the power output at clipping was 50 watts per channel. The short-term (dynamic) power output was 125 watts into 8 ohms, 116 watts into 4 ohms, and 58 watts into 2 ohms, for an 8-ohm dynamic headroom of 1.67 dB.

At 1,000 Hz (8 ohms) the distortion was 0.003 per cent from 0.1 to 1 watt output, rising gently to 0.008 per cent at 40 watts and 0.011 per cent at 100 watts. The 4-ohm distortion was only slightly higher, from 0.003 per cent at 1 watt to 0.008 per cent at 20 watts and 0.05 per cent at 85 watts. Even 2-ohm operation did not increase the distortion significantly; it ranged from 0.007 per cent at 0.1 watt to 0.018 per cent at 20 watts and 0.071 per cent at 40 watts.

The 8-ohm distortion at the rated 85 watts output was less than 0.02 per cent over most of the midrange (from 50 to 5,000 Hz), reaching 0.036 per cent at 20 Hz and 0.04 per cent at 20,000 Hz. The distortion curves at half and one-tenth power were similar in shape but with lower values. At about 8 watts (—10 dB) output, for example, the distortion was between 0.005 and 0.02 per cent over the entire audio range.

The sensitivity of the amplifier for a 1-watt reference output was 16.5 millivolts (mV) for aux and 0.23 mV for phono (MM). The signal-to-noise ratio (S/N) was the same for both inputs, a very good 83 dB (A-weighted). The MC sensitivity was about ten times higher than the MM sensitivity. The phono (MM) overload input was between 131 and 157 mV over the 20- to 20,000-Hz range. The MM input termination was 47,000 ohms, shunted by a capacitance of 100 picofarads.

At input frequencies of 18,000 and 19.000 Hz the IHF IM (intermodulation) distortion was very low, with a second-order component at 1,000 Hz that was 95 dB below 85 watts. The third-order components at 17,000 and 20,000 Hz were each 90 dB below the rated power. The amplifier’s slew factor was greater than 25 (our measurement limit), and it was stable with various reactive loads. When we tried to drive a high-level 10,000-Hz square wave into a low-impedance reactive load, the internal protective relay always shut down the amplifier before any damage could occur. Operation was restored automatically when the signal was reduced or removed.

The tone controls had reasonable characteristics, although the midrange level was shifted by several decibels when both controls were set to their extremes (about ± 12 dB for the bass and ± 10 dB for the treble). The frequency response was extremely flat (less than 0.2 dB overall variation from 20 to 20,000 Hz) when the tone controls were set to their middle positions. The subsonic filter reduced the response by about 2.5 dB at 20 Hz. The high filter cut the response by 3 dB at 4,500 Hz, with a 6-dB-per-oc-tave slope at higher frequencies. The phono equalization was nearly perfect, within 0.1 dB of the ideal RIAA response from 20 to 10.000 Hz and down only 0.5 dB at 20,000 Hz. It was completely unaffected by cartridge inductance.

Since many FM-tuner performance parameters are affected by i.f. bandwidth, we measured the FM section using both wide and narrow bandwidth settings. The mono usable sensitivity was 12 dBf (2.2 microvolts, or μV) in wide and 11 dB (2 μV) in narrow. In the wide-band mode the stereo threshold was 23.3 dBf (8 μV), but in the narrow-band mode it was only 12.4 dBf (2.3 μV). The more important 50-dB quieting sensitivity was almost the same for both conditions: wide-band, 15 dBf (3 μV) for mono and 37.7 dBf (42 μV) for stereo; narrow-band, 13.8 dBf (2.7 μV) for mono and 36.6 dBf (37 μV) for stereo.

At an input level of 65 dBf (1,000 mV), the tuner distortion was 0.11 per cent for mono and 0.15 per cent for stereo with the wide i.f. bandwidth, and with the narrow bandwidth the distortion readings were 0.135 and 0.2 per cent, respectively. The noise level in the tuner output was not affected significantly by the i.f. bandwidth, measuring —76 dB for mono in either the wide or narrow mode. In stereo the noise was either —72.5 dB (wide) or —70 dB (narrow). When we measured the IHF IM distortion of the tuner, which was typical of most good tuners we have measured in this way (using modulating frequencies of 14,000 and 15,000 Hz), the distortion components in the narrow-band mode were typically about 4 to 5 dB higher than in the wide-band mode (though they were negligible in either case).

The stereo FM frequency response was flat within ±0.5 dB from 30 to 10,000 Hz, rising to + 1.5 dB at 15,000 Hz (despite this high-frequency rise, the 19-kHz pilot carrier was suppressed to a safely low —65 dB). The stereo channel separation was unusually uniform, measuring between 38 and 41 dB over the full 30- to 15,000-Hz range in the wide-band mode and between 30 and 33 dB over that same range in the narrowband mode.

As expected, the capture ratio was affected by the i.f. bandwidth. In wide-band it was a very good 1 dB at 45 dBf (100 μV), and it was 2 dB with the narrow bandwidth. The respective AM-rejection measurements were 55 and 60 dB. Naturally, selectivity was very much a function of bandwidth, with alternate-channel measurements of 77 dB and 49 dB for narrow- and wide-band conditions, respectively. Adjacent-channel readings were 7 and 4.3 dB, respectively. The FM image rejection was 76 dB. The muting and stereo-threshold signal levels were approximately the same. The FM-tuner hum level was —63.5 dB (predominantly at 60 Hz). The AM-tuner frequency response was down 6 dB (from the relatively flat midrange level) at 26 and 2,350 Hz.

Comment

Clearly, the J.C. Penney Model 3285 is a lot of receiver, with almost every control or operating feature one could desire (loudness compensation was just about the only noticeable omission, and most people would hardly miss it, especially with the memory tone controls). More to the point, everything on the receiver worked just as it was meant to. We experienced absolutely no bugs or quirks in either its measurement or its operation. Although we usually make no mention of the fact, since it is a function of our test setup and has no bearing on a product’s suitability for home system use, most receivers and amplifiers exhibit some degree of instability under certain test conditions where we require simultaneous access to the input and output circuits. This can greatly complicate the measurement process. It was gratifying to find no trace of this effect during our testing of the Model 3285.

The performance measurement figures speak for themselves—this is a first-rate receiver. It is distinguished from its peers largely by its knobless control design. We have seen this tried before, usually with some sacrifice of either performance or convenience, but this receiver was every bit as easy to use as any with conventional controls. And the excellent circuit-status display gives an accurate visual depiction of the actual settings of the controls.

Over the past several years we have tested several J.C. Penney receivers, and it is interesting that all of them have been very competent performers, hardly what we would expect from a mass-market retailer that does not specifically court audio enthusiasts. We have also noted a growing sophistication in the design of each new generation of Penney receivers. The Model 3285 takes another sizable step in the same direction, and it is quite attractively priced as well.

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