Ive dropped the 2 lme 49720's in this morning and run through a couple of cd's so far. Made sure I used the zap strap so i didn't fry the chip with static and used a sucker to desolder the lm833's, couldn't get any braid locally so ive sacked that for now. I'll order some though and give it a go when the cd371 arrives.
Didn't get any sockets either, again something i'll do to the 371.
Re the iron I use, its a precision gold a55kj. not a top dollar iron by any means, but really nice to use, with 3 user selectable temp settings which have made this project abit easier with the smallest tip. I did have a maplins blue temperature controlled iron which was ok, this one is much better.have steady hands, but crap eyesight, must invest in a magnifier at some point.....
There is quite a difference with the new op amps, it seems easier to listen to if that makes sense, no need to strain to follow an instrument, its just there. Marginally better imaging, marginally better depth. More subtle. Less shouty.
Bass is much more controlled, and that signature early cd screech seems to be much improved. Details are easier to pick up and follow.
It seems more natural, more atmospheric. The little details are there. Especially at the top on things like ride cymbals and the like.
I looked at the datasheet for both the original and new op amps, the lme's thd is quoted as 0.00003%, the lm833n is quoted as 0.002% so there is a pretty good explanation for what i seem to be hearing, in terms of it sounding more natural.
If its oscillating I cant tell, only way to see would be to scope it.
Neil Young's harmonica on his unplugged album isn't wince inducing now
I'd say mod number 2 is a successful upgrade over standard rather than just being a sideways move which is always a possibility.
Next step, maybe a set of regs?, change the 1541 decoupling caps?, swap out all the axial caps on the board? swap out the nichicon fw lytic output caps for something else?, clock upgrade?
I have read people have removed the muting transistors, but im not sure why as they dont seem to be in the signal path on rhe cct in the service manual, they appear to drop off the track that goes to the sockets rather than the signal going through them and out. So i cant see any point in doing that unless someone knows better and ive missed something fundamental which is entirely possible
Suggestions welcome on step 3
Im finding this quite an enjoyable little side project