Here we've got a nice Kenwood C2 pre-amplifier. The unit came in for an overall recap and OPAMP upgrade. Leestereo of Audiokarma was very helpful with additional OPAMP information from his Kenwood C1 rebuild, big thanks to him and his work, truly top notch.
open-booked main PCB assembly
Each stage has its own power supply, where as the electrolytic were replaced with high temp long Panasonic FR/FC capacitors, I prefer this application vs a audio grade. In a power supply were looking for an extremely reliable capacitor, the Panasonic FR/FC series deliveries just that.
Note that the phono/tone/flat amp stages feed a 18.6-18.5Vdc rail to each OPAMP quadrant. the rated parameters of the NJM4580 and NJM2068 OPAMPs are 2-18Vdc. For continued longevity of the OPAMPS D13/14/11/12 should be replaced with a 16-17Vdc zener to drop that operating 18.5-6vdc rail voltage.
The following OPAMPS were upgraded along with new gold contact 8 pin DIP sockets for future rolling;
Phono - NJM2068DD
EQ stage - NJM4580DD
Tone Control - NJM4580DD
Filter stage - NJM4580DD
For all other electrolytic Elna Silmic or Bi-Polar MUSE ES were utilized, all low value lyrics were replaced with a polypropylene ECW Panasonic film capacitor.
I have to say, pairing this C2 with a Nikko 440 Alpha amplifier is quite impressive. There was a notable difference between the the original 2041DD JRC OPAMP and the NJM2068DD OPAMP. Impressed….
Excellent job on recapping and upgrade and thank you for the pictures and information! I got a Kenwood C-2 Pre-amp about a month ago and I have been testing various ways of running it in my system. I was considering doing some op-amp upgrades, do you think this pre-amp would benefit from discrete opamp designs, such as Burson Audio's V5 & V6 OPA series? If you had two pairs of mono and dual V5-OPAs on hand, where is the best location from the 4 options. BTW, most people are too lazy to add sockets, but like you I also add sockets to almost anything I can, especially if I plan on measuring various hardware scenarios. I even have both full and half can oscillator sockets! Keep up the good work, sorry for the 2 year delayed praise, lol. If bored check out my website that is also heavily audio based: www.zosoncsu.com
ReplyDeleteKeep up the great work!