I just completed the mod. All I can say initially is Wow, what a substantial difference in the sound. I listened to some FM and 2 albums (Heartsfield and the Beatles blue album). Vert crisp, clean highs and smooth bass. I have the complete Kenwood Basic system I purchased new several decades ago; C1 pre-amp, M2 amp, GE-1100 equalizer, T1 tuner, X1 cassette, KD-72B turntable and an odd ball Pioneer RT-707 reel, with Bose 901's. My only issue I had was I ordered the wrong caps for the Flat amp C25 and C26 so I reused the original caps. I checked and double checked the list before I placed the order with Mouser and still missed them; right size wrong type (should be Nichion Muse). I don't know if the originals have that much effect on the overall sound. I will order the correct ones with my next order and replace them. One other notable issue are the 1uF Panasonic stacked polyester film capacitors are no longer available. Neither Mouser or DigiKey carries them. They went out of production in 2015. I was able to find some Nissie ones on eBay but had to buy a lot of 25. Parts on Mouser were $36.78 (I order a second set of different opamps to try also) and the eBay order was $10.99. Not a bad investment for so much better sound and cheaper than overpaying for a C2 pre-amp on eBay.
The instructions included up in thread are very good and provide all the detail needed to complete the mod. The only missing component in the directions was the cap on the bottom of the large board but that was it. What made it a bit easier before I started was lay out 4 sheets of paper and labeled them power supply, tone amp, flat amp and phono. Place all the parts outlined in the directions on the appropriate paper and then start removing the components for each section. Insert the new parts, solder and inspect. Move to the next section. Keep in mind with the caps the long lead is the '+' side and the zeners have to be installed in the correct orientation and the boards are marked as such. Other than that, parts can be install in either direction.
You'll need a good solder sucker, soldering iron, solder, and needle nose pliers. A good LED flashlight, and magnifying glass to check your soldering is a must. I think there is about 120 or so points to solder so it takes quite a bit of time. Take breaks and pay attention to details. DO NOT rush. The last thing you want is sparks flying when you plug in and hit the power switch. If you lack good soldering skills I would not suggest diving into this mod until you practice on something else. You want to make quick joints so you don't overheat the components especially the tiny caps, resistors and zeners.
Let me know if you need any info. I'll help as much as I can. It was a fun little project. I'm glad I did it. Even my wife can tell the difference and that made it worth while
I also want to thank Leestereo for all the upfront work to make this mod a reality. Thank you.
Dave
