Hi…
This is what I did..
1-I removed the “X” opamp and replaced it with a ad8620
2-Added some extra caps in the small p.s board in the player.
The d-25 has this “Dual ground sense operational amplifier “ ->
http://www.rohm.com/products/databoo...df/ba10358.pdf I found this by chance while trying to salvage a d-25 to repair a d-555… since it is a cheap opamp I thought that maybe it could be replaced. And I did…(without really knowing what the purpose of this opamp is..but I assumed is the analog output)
the player feeds 6v to the opamp (measured using pin 4 and 8).. now the weird part is …the d8620 is not supposed to work with this voltage and the player shouldn’t sound at all…right??..well..it does sound fine.. but now I think that maybe this opamp is not the output one (otherwise it would sound like crap because the low voltage …right??)
After replacing the opamp I noticed a slight lost of volume from the headphone jack (it still has more that necessary..), I also noticed a “increase” (small) of the bass and I don’t know if that makes it to sound a little more relaxed in the highs, but it sounds a little more “round”…not that sharp, I mean….. and maybe it added a little hiss sound (“detail”?? in bad recordings..)
I also added 2 extra 150uf caps in the power supply (now total is 450uf) so maybe that is the reason for the bass change….could be …
Sorry my approach is so un-scientific…I wish I could give more details
i will try to intall the old opamp and compare again....
m.