Kenwood KN-6644 (c. 1971)
The TRIO KN-6644 was sold under the Kenwood name in some markets. It's one of the more obscure pieces of early-1970s quadraphonic hardware. It's described as a "Surround Sonic quadrixer," a 4-channel preamplifier/processor that let you enjoy 2-channel sources with 4-channel realism. The period price was ¥49,800.
The KN-6644 is flexible. It supported all four playback circuit systems of the era: discrete, quadrix, delay, and a combination of quadrix plus delay. The unit included encoder and decoder circuits, so you could encode 4-channel sources for recording onto 2-channel media, or decode 2-channel sources into 4-channel playback. It also had a direction switch to rotate the front image (front, back, left, right), a rear position control, and a mixing knob that moved the rear sound field forward or backward without physically moving speakers. In Hall 1 mode, a delay component was added to the quadrix signal for a concert-hall-like tone. In Hall 2 mode, only the delayed component played from the rear speakers.
The Audio Database entry gives the fullest technical picture. Input sensitivity was rated at 200mV/30kΩ for both 2-channel and 4-channel Aux/Tape inputs. Maximum power output was 4V for both 2-channel and 4-channel, and maximum output was 4.5V (High). Frequency response in 4-channel mode was 20 Hz to 20 kHz +0/-1dB for both front and rear. In 2-channel mode, front was ±1dB and rear was +1/-2dB. Signal-to-noise was 75dB front in both modes, 70dB rear in 2-channel, and 75dB rear in 4-channel. Delay time ran 20-35 m/sec, reverberation time 0 to 2.3 seconds, and power consumption was 20W. It measured 495 x 134 x 271 mm and weighed 6.9 kg.
Surviving documentation is thin. The unit appears in Russian marketplace listings, where it's described as "extremely rare" and a "masterpiece from TRIO," with one current asking price around 230,590₽. A Russian forum entry calls it a "stereo/quadro preamplifier, equalizer." No owner reviews with detailed listening impressions, no production quantities, and no service history are documented. Its position in the TRIO/Kenwood lineup relative to the KA, KR, and Supreme series is also unrecorded.
What's known in brief:
- Quadrixer preamplifier, 4-channel, c. 1971 — ¥49,800
- Supports discrete, quadrix, delay, and quadrix+delay playback
- Encoder/decoder circuits for 4↔2 channel conversion
- Direction switch, rear position control, mixing knob
- 20W power consumption; 495 x 134 x 271 mm; 6.9 kg
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