That's right. A few upgrades and tweaks for the old gal.

On the list will be opamps, wiring reroutes and upgrades, power supply changes.

First up, I'm going to remove these JRC4735B opamps (assuming I have correctly identified them) and replace them with...dunno. After reading up a bit it appears that these are part of the problem with this player sounding so dark. I'll have to do some comparisons, but it seems like an OPA2134 could be a candidate, or an AD8610 (or 20). Guesses? I'll have to check the pinouts to be sure.

Make that the JRC4558 opamp.

I'm not seeing a lot of praise for the OPA2134, but am seeing some good things about the OPA627/637. As for the AD8620, reviews seems to be the same as they were before: rather clean sound, and can be too steril with the wrong associated circuit. I may just solder in a few sockets and roll these until the rest of the changes are made.

Additionally, it doesn't look like these are biased to Class A, but I'll have to poke around at the traces to figure that out. I'm doubting it, though.

Opamp preferences, anyone?

Any guess what parts L901 and L902 are? Measured, they don't seem to be...anything. They are on the output path to the RCAs on the back panel. I assume they are some kind of output cap. Guesses?

Edited July 8, 201115 yr by bhjazz

Maybe ferrite beads?

Sure look like it.

Yep. L normally signifies an inductor of some type, and those do look like ferrite beads. C is normally used to denote a capacitor, and R a resistor.

Ah. Sweet. Thanks, guys! That makes sense since the photo is of the corner of the power supply board (and the audio circuit runs along side the power supply.)

Edited July 8, 201115 yr by bhjazz

Quick question: If I get the audio portions of the circuit off of the PW board, do I still need the ferrites? Doesn't seem like it would hurt anything, but I'm just curious. Thanks!

quick question. Do you have measurement equipment to determine if removing stuff off the board causes problems?

The ferrites remove high frequency trash, and may keep the output

opamps from oscillating under some conditions. If you are going to

replace the entire output section, then you can remove them, but

they are there to limit stuff over 100khz.

quick question. Do you have measurement equipment to determine if removing stuff off the board causes problems?

File my answer under "I wish" or "Hell, no"! Good point. I don't think a typical DMM would fit that classification.

The ferrites remove high frequency trash, and may keep the output

opamps from oscillating under some conditions. If you are going to

replace the entire output section, then you can remove them, but

they are there to limit stuff over 100khz.

OK. I'll leave them in, then. Thanks.

So, these are more of a subjective, "yeah, sounds better leave it in"? Seems like a lot of guessing to me, hope you have really good ears.

Well, I'm no expert. That's why I ask here. I'll still A/B the suggestions, but I like to have a general path to follow. In the end, it's still a $150 CD player so experimentation is just experiementation.