Kenwood KA 8000 (1978)
A high-performance stereo integrated amplifier
Overview
The Kenwood KA 8000 is a stereo integrated amplifier manufactured by Kenwood and released in 1978. The amplifier is part of the KA series and features a sophisticated design focused on minimizing signal path distortion through full DC coupling and a unique Σ drive system that extends negative feedback to the speaker input terminals.
Specifications
| Rated Output (20 Hz to 20 kHz, Both Channel Operation, 8 Ω) | 55W + 55W |
| Rated output (1 kHz, 4 Ω) | 110W + 110W |
| Rated output (1 kHz, 8 Ω) | 85W + 85W |
| Total Harmonic Distortion (Tuner/AUX/Tape, 20Hz-20kHz at rated output, 8 Ω) | 0.009% |
| Total harmonic distortion (Phono to SP, 20Hz-20kHz at rated output, 8 Ω) | 0.02% |
| Total harmonic distortion (Tuner/AUX/Tape, 1 kHz at rated output, 8 Ω) | 0.004% |
| Total harmonic distortion (Tuner/AUX/Tape, 20Hz-20kHz at 1/2 rated output, 8 Ω) | 0.008% |
| Intermodulation distortion factor (60Hz:7kHz=4:1, rated output, 8 Ω) | 0.009% |
| Frequency characteristic (Tuner/AUX/Tape → SP, DC on) | DC ~ 400 kHz -3dB |
| Frequency characteristic (Tuner/AUX/Tape → SP, DC off) | 18 Hz to 400 kHz -3dB |
| Output Bandwidth (IHF, 8 Ω at 0.03% distortion) | 5 Hz to 65 kHz |
| Damping factor (100 Hz, 8 Ω) | 100 |
| Input Sensitivity / Impedance (Phono MM) | 2.5mV/47k Ω |
| Input Sensitivity / Impedance (Phono MC) | 0.2mV/100 Ω |
| Input Sensitivity / Impedance (Tuner/AUX/Tape) | 150mV/47k Ω |
| Signal-to-noise ratio (IHF-A, Phono MM) | 84 dB |
| Signal-to-noise ratio (IHF-A, Phono MC) | 64 dB |
| Signal-to-noise ratio (IHF-A, Tuner/AUX/Tape) | 105 dB |
| Tone control (Bass, 100 Hz) | ± 7.5 dB |
| Tone control (Treble, 10 kHz) | ± 7.5 dB |
| Loudness control (Volume -30dB) | +10dB(100Hz) |
| Subsonic filter (-3dB) | 18 Hz, 6dB/oct. |
| Rise time (Tuner/AUX/Tape → SP) | 1 μs |
| Slew rate (Tuner/AUX/Tape → SP) | ± 100 V / μs |
| Phono maximum allowable input (Rec out, 1 kHz, 0.01% distortion) | MM: 220 mV; MC: 8 mV |
| Phono RIAA deviation | 30 Hz to 20 kHz ± 0.3 dB |
| Output Level / Impedance (Tape rec) | 150mV/220 Ω |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Rated power consumption | 160W |
| Power outlet (switch interlocked) | 2 systems |
| Power outlet (switch not linked) | 1 system |
| External dimensions | Width 440 x Height 123 x Depth 375 mm |
| Weight | 13.5kg |
Design
The Kenwood KA 8000 uses a pre-main amplifier design with Σ drive, a system that treats the speaker cable as internal amplifier wiring and applies feedback directly at the speaker input terminal to reduce distortion. It is a straight DC amplifier with no coupling capacitors in the signal path from input to output, including the feedback loop. The amplifier employs a cascode-connected FET differential input stage, direct-coupled ICL, OCL, and DC power amplification, and a high-gain power amplifier section. The power supply uses a dual-wound transformer and four 10,000 μF capacitors with independent left/right channel regulation. The MM/MC phono stage uses low-noise ICs and a gain switch (35.6 dB for MM, 57.6 dB for MC) without requiring plug changes. The tone control uses a main tone system with an operational amplifier, and the unit includes a fader system with preset volume and dual-color illumination.
Market
The Kenwood KA 8000 has been listed for sale at CAD $400.00 Estimated market value ranges from $400 to $800 depending on condition and restoration quality.
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