The suggested retail prices of the Kenwood C-1 and M-1 are $225 and $330, respectively.
The Sigma Drive circuit operates only on the speaker-A outputs, and the speaker-B terminals are two sets of conventional binding posts. On the rear of the M-1 are large insulated binding posts for the speaker outputs (including an extra pair of sigma sensor terminals for each of the speaker-A outputs), the input phono jacks, and three a.c. This allows the negative feedback to compensate for any losses or other undesired effects in a long speaker cable, and it requires either a special four-wire cable or the use of two wire pairs per speaker. The technique essentially extends the negative-feed-back path of the amplifier to the speaker terminals themselves instead of only to the amplifier output terminals, as is usually the case. The M-1 features the Sigma Drive circuit introduced by Kenwood a couple of years ago. It also has a front-panel headphone jack. The M-1 has no controls on its panel other than the square power button (with an adjacent pilot light) and two narrow pushbuttons for independent (not simultaneous) operation of two sets of speakers. Its response is rated at - 3 dB at 1 Hz and 300 kHz, with a slew rate of ± 100 volts per microsecond. Like the preamplifier, the M-1 is a wideband design. The dynamic-output rating of 210 watts per channel into 4 ohms implies a good current-delivery capability. Although the M-1 has no formal power rating for lower load impedances, Kenwood does specify its 1,000-Hz clipping-power and dynamic-power outputs into both 8 and 4 ohms, as well as the corresponding headroom ratings. The companion M-1 power amplifier carries a rating of 105 watts output into 8-ohm loads from 20 to 20,000 Hz with no more than 0.005 per cent total harmonic distortion. The rated output is 1 volt, with a maximum output of 5 volts before clipping sets in. They include distortion of less than 0.005 per cent at a 1-volt output from any signal source and a frequency response down by 3 dB at 1 Hz and 250 kHz. The performance specifications of the C-1 are impressive, especially in view of its modest price. convenience outlets, one of them unswitched. On the rear of the C-1 are phono jacks for the various signal inputs and outputs and for the two preamplifier output jacks. Unlike most loudness controls, this one acts independently of the volume setting. At the loudness knob's farthest counterclockwise setting the loudness compensation is off, and turning the knob progressively clockwise adds a low-frequency response boost. The other front-panel controls of the C-1 are a large volume control, small center-de-tented knobs for bass and treble tone controls and the balance control, and a loudness knob. The power switch is a large square button at the left of the panel. A smaller button turns on the subsonic filter, which rolls off the response at 6 dB per octave below 18 Hz. All signal selection is by means of narrow rectangular pushbuttons (mechanically interlocked) with red LED's above them to show when they are engaged.
There are input and output facilities for two tape decks, and selecting both simultaneously connects them for dubbing from deck A to deck B. The C-1 has inputs for two high-level sources (aux and tuner) and a single phono cartridge with front-panel switching for either a moving-magnet (MM) or a moving-coil (MC) type. The units are finished completely in flat black, with controls of the same color.
The M-1 power amplifier, the same width, almost exactly the same depth, and 4-7/16 inches high, weighs 20 pounds. The C-1 preamplifier, 17-5/16 inches wide, 12-7/8 inches deep, and about 3 inches high, weighs 9-1/2 pounds. The C-1 and M-1 are matched in size, appearance, and function, forming a very high-quality amplifier system of moderate cost.
Kenwood's Basic C-1 preamplifier and Basic M-1 power amplifier are part of its "Audio Purist" series of high-fidelity components.