Kenwood Basic C2 Preamp #1 - $250 (Hubbard)

Kenwood Basic C2 Preamplifier #1

I'm selling two of these. See my other listing for the second unit.

This has low self-noise and distortion and wide frequency response. The phono preamp supports MM and MC cartridges and has 5 impedance settings.

Looks good, with the exception of a few dings in the top edge of the front panel. Works great, except that the right channel is a little louder than the left channel. This may be related to the volume pot or something else that I didn't address. It sounds really good. Many hours of work have gone into restoring and improving the performance of this unit. 

I will sell this with the matching Basic M1D power amp for $500 total (that one is listed separately as well).

I am an electrical engineer and have done the following work:

• Replaced polarized electrolytic capacitors with Panasonic FC or FR (105°C), Panasonic film, or WIMA film, as appropriate. Most of this was done in 2013, and the unit has seen very little use since then. The other work was done in October 2026.
• Replaced bipolar electrolytic caps with Nichicon Muse ES.
• Replaced NJM4560DN op-amp in phono preamp with NJM4580DD in a DIP socket. This has lower noise than the original.
• Replaced NJM4560DN op-amp on the control board and the filter board with NJM2068DD. These has less noise than the original.
• Replaced (4) JFETs in the phono preamp input stage with a precisely matched set of the same model. Two of the originals had failed.
• Replaced (4) 20V zener diodes with 18V. This brings the voltage rails on the op-amps to ~17.2V so that they will last longer. (The op amps are rated for 18V maximum and the original design exceeded that limit.)
• Replaced (4) rectifier diodes with UF4005. These are faster and more robust than the originals.
• Replaced most ceramic capacitors with WIMA polypropylene film or TDK type C0G ceramic, as appropriate. Did not replace: 2 caps across the power supply input; 2 caps on the back side of the headphone preamp; 2 caps on the balance board.
• Bypassed the balance pot with (2) 180 kohm metal-film resistors. The pot had failed and there is not a drop-in replacement; this is a typical mod on these units. The pot is still in place but is disconnected.
• Replaced resistors in the signal path, on the main board only, with Vishay Dale Type CCF 1% metal film. This might provide a small reduction in noise, particularly in the phono preamp.
• Cleaned all switches and potentiometers with appropriate DeoxIT products.
• Removed, disassembled, and thoroughly cleaned the Tape, Source, and Phono selector switches. Each has 52 solder joints and six moving contacts. This part of the project required several hours, but (at least for the Tape and Source switches) is essential to prevent crackling and dropouts. It is not sufficient to spray DeoxIT from the outside of the switch.
• Cleaned all RCA jacks, inside and out, with DeoxIT.
• Tested all inputs, outputs, and switch positions.
• Cleaned exterior. 

 Partial specifications:

• Input Sensitivity/Impedance/Signal-to-Noise Ratio (IHF A Curve)
  • Phono MM: 2.5 mV/30 k, 47 k, 100 k ohms/88 dB
  • Phono MC: 200 µV/100 ohms, 200 ohms/70 dB
  • CD, AUX, TUNER, TAPE: 150 mV/47 k ohms/110 dB
• Signal-to-Noise Ratio Unweighted at 50 mW (DIN)
  • Phono MM & MC: 73 dB
  • CD, AUX, TUNER, TAPE: 79 dB
• Maximum Input Voltage for Phono MM: 200 mV, T.H.D. 0.002%
• Maximum Input Voltage for Phono MC: 15 mV, T.H.D. 0.002%
• Frequency Response
  • Phono MM & MC: 20 Hz - 20 kHz ± 0.3 dB
  • CD, AUX, TUNER, TAPE: 1 Hz - 350 kHz (– 3 dB)
• Tone Control
  • BASS turnover: 400 Hz: 100 Hz ± 10 dB
  • turnover: 200 Hz: 50 Hz ± 10 dB
  • TREBLE turnover: 3 kHz: 10 kHz ± 10 dB
  • turnover: 6 kHz: 20 kHz ± 10 dB
• Filter
  • Subsonic: 18 Hz, 12 dB/Octave
  • Low: 40 Hz, 12 dB/Octave
  • Subsonic + Low: 58 Hz, 12 dB/Octave
  • High: 8 kHz, 12 dB/Octave
• Transient Response
  • Rise Time: 1.0 µs
• Total Harmonic Distortion
  • CD, AUX, TUNER, TAPE
    • 20 Hz - 20 kHz: 0.001% at 1 V Output
  • Phono MM & MC
    • 20 Hz-20 kHz: 0.002%
• Output Voltage & Impedance
  • TAPE REC: 150 mV, 220 ohms
  • PRE OUT: 1,000 mV, 100 ohms
• Loudness Control
  • (at VOLUME - 30 dB): 100 Hz, + 6 dB
  • (at VOLUME - 40 dB): 100 Hz, + 9 dB

I can demonstrate this unit in Hubbard. I am available most evenings, and some other times, Monday through Saturday. Click the “more ads by this seller” link to see other items I’m selling.

Keywords: amp, amps, power amp, Rotel, Pioneer, Marantz, Sony, Denon, NAD, Sansui, Yamaha, preamplifier