bhjazz Posted June 17, 2011 Report Share Posted June 17, 2011 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. Quote Link to comment Share on other sites More sharing options...
bhjazz Posted June 17, 2011 Author Report Share Posted June 17, 2011 Make that the JRC4558 opamp. Quote Link to comment Share on other sites More sharing options...
bhjazz Posted June 28, 2011 Author Report Share Posted June 28, 2011 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? Quote Link to comment Share on other sites More sharing options...
bhjazz Posted July 8, 2011 Author Report Share Posted July 8, 2011 (edited) 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, 2011 by bhjazz Quote Link to comment Share on other sites More sharing options...
mypasswordis Posted July 8, 2011 Report Share Posted July 8, 2011 Maybe ferrite beads? Quote Link to comment Share on other sites More sharing options...
cetoole Posted July 8, 2011 Report Share Posted July 8, 2011 Sure look like it. Quote Link to comment Share on other sites More sharing options...
Pars Posted July 8, 2011 Report Share Posted July 8, 2011 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. Quote Link to comment Share on other sites More sharing options...
bhjazz Posted July 8, 2011 Author Report Share Posted July 8, 2011 (edited) 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, 2011 by bhjazz Quote Link to comment Share on other sites More sharing options...
bhjazz Posted July 8, 2011 Author Report Share Posted July 8, 2011 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! Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted July 8, 2011 Report Share Posted July 8, 2011 quick question. Do you have measurement equipment to determine if removing stuff off the board causes problems? Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted July 8, 2011 Report Share Posted July 8, 2011 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. Quote Link to comment Share on other sites More sharing options...
bhjazz Posted July 8, 2011 Author Report Share Posted July 8, 2011 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. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted July 8, 2011 Report Share Posted July 8, 2011 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. Quote Link to comment Share on other sites More sharing options...
bhjazz Posted July 9, 2011 Author Report Share Posted July 9, 2011 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. Quote Link to comment Share on other sites More sharing options...
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