A Compact and Very Unconventional Amplifier
Technics Model SE-C001 stereo/mono power amplifier, in metal case. Dimensions: 11 3/4 by 2 inches (front panel), 8 1/4 inches deep plus clearance for heat sink (at least 1 1/2 inches) and on/off switch. Price: $360. Warranty: "limited," two years parts and labor.
Manufacturer: Matsushita Electric Co., Japan; U.S. distributor: Panasonic Co., Div. of Matsushita Electric Corp. of America, 1 Panasonic Way, Secaucus, N.J. 07094.
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Technics Model SE-001 Power Amplifier
Stereo (unstrapped)
Manufacturer's rated power 16 dBW (40 watts)/ch.
Power output at clipping (both channels driven)
into 8 ohms 17 3/4 dBW (52 watts)/ch.
into 4 ohms 16 1/2 dBW (45.5 watts)/ch.
into 16 ohms 15 3/4 dBW (33 watts)/ch.
Dynamic headroom (at 1 kHz) 0 dB
Frequency response
+0,-'V. dB, <10 Hz to 38.8 kHz
+0,-3 dB, <10 Hz to 260 kHz
Input characteristics (re 0 dBW; noise A-weighted)
sensitivity 150 mV S/N ratio 90 1/2 dB
Harmonic distortion
Mono
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An unusual beast, this amplifier. In the first place, Technics has designed a switching power supply for it to dispense with the traditional bulky transformer that otherwise would tend to swell it beyond its modular-micro format. In the second place, the company includes a strapping feature to convert the SE-001's basically stereo circuitry for mono operation-a feature common in public-address and other commercial-application amps but not in home gear. And both aspects of the design have some rather surprising ramifications.
The switching power supply leaves some residual of its switching frequencies in the output, which therefore would make unweighted noise measurements (ours are A-weighted) appear poor. The switching frequency always is above 20 kHz, so it is (at least in theory) inaudible. The exact frequency changes somewhat, depending on how hard the amp is driven; it showed up anywhere between 21 and 27 kHz in the bench tests at DSL. The amp gets noticeably warmer than most contemporary power amps, though you should be able to avoid outright misadventure by heeding Technics' warnings about allowing the SE-001 proper ventilation and keeping it from sources of heat. There does seem to be current limiting in the design.
Note that maximum output power into a 4-ohm load is a little less-not more-than that into an 8-ohm load, though the actual power level in both cases is above Technics' rating of 40 watts per channel.
When a strapping switch on the bottom of the amp is used to convert it to mono use, more surprises show up. As it turns out, however, the surprises are occasioned less by actual performance than by Technics' specs-which, on paper, make it appear that the mono strapping is almost worthless. We might assume that the feature was provided so that owners wanting to increase the power of their systems could buy a second amp and use each-strapped--for one channel of the stereo pair. But Technics' own power claim in the mono mode is a mere 1 1/2 dB above the per-channel stereo rating. Big deal! On the bench, however, it turns out that clipping power is 2 dB higher into 8 ohms and 5 1/4 higher into 16. (The mono mode is not intended for use with 4-ohm loads.) And with music the difference is even more dramatic. In stereo, the amp actually produces 1 1/4 dB less power before clipping the music-simulating tone bursts of the dynamic-headroom measurement than it does before clipping the steady tones of the regular clipping test; in mono, the dynamic headroom is 1/4 dB above the steady-state clipping level.
So the per-channel power the amp can deliver into 8-ohm loads is 45 watts stereo and 85 watts mono with sine waves and the equivalent of 40 watts stereo and 90 watts mono with the simulated music! In other words (and despite the implications of Technics' specs), you can effectively double the power by adding a second amp.
The oddities made us wonder what we would hear when we used the SE-001 in a listening system. Not to worry: It sounds just as it should. While we would not attribute any distinction to it, its sound is as clean and well defined as that of any regular moderate-power amp (separate or built into a receiver) with which it would occur to Ls to compare the Technics. Distortion is very low (and essentially the same in both operation modes) and generally remains low even if we consider the power-supply switching frequency as "distortion." Checks of intermodulation at high frequencies-which we thought might be aggravated by the switching frequency-were all below 0.075% and dropped to the level of the harmonic-distortion measurements by the time the test tones had descended into the 10-kHz region.
It should be fairly obvious that we don't know quite what to make of this design. Like all the Technics micros, it is elegantly sharp-edged in style and features gold-plated input contacts and non-scratch feet that can be folded down to tilt the amp upward for a better view of its power metering. And somehow the omission of an on/off switch (which Technics expects will be supplied by your-and preferably their preamp) lends some special "feel." But the unconventional behavior of the circuitry is harder to assess. We liked what we heard, and perhaps that is all that need be said.
Also see:
Mitsubishi Model M-T01 cassette deck (review, Jun. 1979)
Technics Model SU-001 stereo preamplifier (review)