Lordy, if its in the C1 it is almost certainly in the C2 as well. I will have to admit right now that it was my fault about the volume level thing. I guess I had the gain / volume level one of the two turned down. Levels are great now. Hope someone chimes in about the resistor change as well as the op amp swaps..Thanks Anti_Skate.I'm not sure about the c2 but in the c1 there was a resistor change when swapping the op amps. Presumably to change the gain of the amp to match the original circuit.
...On the EQ amp there was a 4560DN JRC.... Now, on the flat amp there is a JO41DD JRC (I have not replaced it yet).
In the C1 preamplifier, it is the output load resistors (R41/R42) for the final op amp that are changed to 56.2kohm resistors. This will not affect the gain of the circuit. In the C2, the corresponding resistors are R55/R56 and they are already specified as 56kohm.I'm not sure about the c2 but in the c1 there was a resistor change when swapping the op amps. Presumably to change the gain of the amp to match the original circuit.
OK, after looking again I did find that the "Eq Amp" was the phono section..Took me a while to put it together in my head as I kept looking for the phono section that did not exist so thank you for replying so I know my thinking and reading of the schematic are verified. This is where you recommend a NJM4580DD op amp if my reading of the thread is correct. The other three op amps should be NJM2068DD. If I am reading correctly. Please tell me I am right..I have a slew of op amps now that I ordered wrong somehow. I think I was reading multiple threads at different times as I wrote down the parts I needed. Thanks Leestereo.In the C2 schematic, Kenwood refers to the phono op amp as the "Eq Amp". The flat amp (i.e., line stage) is a 2041DD op amp.
Thank you as I have a C1 that I will restore as well using the information found here. I will not buy a "kit" for the C1 I want to go full tilt upgrade on this one..In the C1 preamplifier, it is the output load resistors (R41/R42) for the final op amp that are changed to 56.2kohm resistors. This will not affect the gain of the circuit. In the C2, the corresponding resistors are R55/R56 and they are already specified as 56kohm.
...This is where you recommend a NJM4580DD op amp if my reading of the thread is correct. The other three op amps should be NJM2068DD...
At this point you have lead me completely thru all I need to know Leestereo. Thank you so.Yes, I suggest using a 4580DD for the phono stage since it has a lower noise specification in a RIAA circuit. And the Flat Amp, Tone Amp and the Filter Amp can all use the 2068DD. Note that if you want to use the aforementioned op amps, you should also replace the 20V zener diodes at D11-D14 with precision (2%) 16V BZX85B zeners to lower the rail voltages (the stock rail voltage is ~18.6V which is too high, even for the stock 4560 op amp).
Glad to help, vsat88.
How do you like your restored/upgraded C1 & C2?