A quick tune up...

I have finally got around to getting the lid off the S300...

With the service manual handy, I checked the bias current setting. It is meant to be set such that you have 75mV between the test points. On one channel I had 63mV, the other 42mV. A quick twiddle of the pots got the setting to within 1mV of 75 (it's very difficult to get precisely right), and believe that I've extracted a little improvement that way (unsurprising really...). It has improved transparency a little.

For those of you who are technically inclined (and own class AB amps), it might be worth checking and, if necessary, setting the bias current.

A quick inspection of some of the componentry and construction also shows some room for improvement. The four big decoupling caps per channel are Nichicon CEs, which are a fairly basic electrolytic, and the smaller caps are Elnas. A few judicious replacements with Stargets, Black Gates or Panasonic FCs as appropriate should improve matters a little. Also, the connections from preamp board to poweramp boards are with rather long pieces of wire... shorter runs of higher quality wire (are you listening WM?) should benefit... same goes for the RCA inputs. Also, some ERS to shield the pot motor and the front panel psu and electronics from the signal circuitry could help too.

 

ignore me
i read decoupling as coupling

 

Who ?, what ?, where ?, I think you have the wrong person sir, your assumption of atoms forumulated into drawn stands of possible ferrious substanices could possibly have ANY effect is spurious at best, as for being a 'Fellow' of certified edicational standards, I feel sir you are grossly misleading the memebers of this forum & should at once forwith withdraw said ' pure conjectured, unsubstanicated, nah malicious totally unfounded and uncorroberated piece of information at once, you cad & bounder sir, you'll be having us believing that dac 64's are valve like next

 

That'll be a yes then?

 

I was wondering, as I did actually read your original post and vaguely wondered...

Before reaching my own conclusion to ignore you.

 

Most do