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Old 3rd August 2013, 02:08 PM   #1
nottstu is offline nottstu  United Kingdom
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Default Improving sony cdp-c661

I have a Sony CDP-C661 CD multiplayer.

I know it's prety old now and it will never be sonically magnificent but I love the convenience of it's 5 disc turntable (my other sources include a modded marantz Ken Ishiwassname so something to approach that would be nirvana!).

Would anyone care to suggsst how I might improve the sonic output of the Sony so I can get more of the benefit of my ae1s and stuff while retaining operational benefits of the turntable.

NB - this is my last hope before succumbing to mp3s so you'll understand the importance!

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Old 3rd August 2013, 02:20 PM   #2
Mooly is offline Mooly  United Kingdom
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I would suggest (and I'm not familiar with the player) looking at replacing the stock opamps used in the output/filter sections. Try something like the OPA2604 (duals) or OPA604 (singles) or the OPA2134/134.

That will probably give the single biggest gain/change in audio quality based on my experience. As ever, the usual warning applies that just occasionally swapping opamps can be less than straightforward with regard to stability issues although I wouldn't really envisage any on a standard Sony which probably uses a totally conventional circuit. Beyond that and any output muting (if done with transistors) can be worth a look. A worthwhile mod is replacing these with suitable FETs as long as the voltage drive is suitable.
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Old 3rd August 2013, 02:22 PM   #3
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Would an external DAC be an option?
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Old 3rd August 2013, 03:38 PM   #4
nottstu is offline nottstu  United Kingdom
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Thanks guys.

I did wonder about an external DAC but it's an extra 13amp socket and I wasn't sure the expense could be justified with what I presume to be the mechanical/optical limitations of the Sony.

Any comments on that would be appreciated.
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Old 3rd August 2013, 10:23 PM   #5
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Manual free here if you register. There's a list of how that model varies from the machine you've got, somewhere, but I don't think you need it.

Erm...you'll need to think carefully before spending much money on it, IMO.

Its DAC appears to have no reputation and I can't find a datasheet. It is differential voltage output judging by the following circuit. You might like the sound of it, but at the moment you can't really tell.

The opamps are 4558. What you might replace them with is a matter of strategy. The supply to the audio stage is +10.9, -12.1, unregulated and with only rudimentary smoothing. As it is, replacement opamps should have very good PSRR to reject ripple and noise. If you add regulation with low dropout regs, you'll need opamps happy with +/-9V. If you don't regulate, you could improve with small chokes and extra caps without losing voltage.

Change all the ceramic caps in the audio stage for C0G (or NP0) unless that's what they already are (I doubt it). That would be easy, effective, and cheap.

Change the output caps to bipolar maybe. Depends on the quality of what's there. If I think there's a polar cap in my signal path, the sound deteriorates. A poor quality electrolytic actually does measurable damage.

The laser mech is common and OK. Easily replaceable if it croaks, AFAIK.

If you feel the changer gubbins are in good order and work well, the quality of its output is as good as anything else. It could be a machine that your friends laugh at, but actually they can't hear the difference.
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Old 5th August 2013, 07:43 AM   #6
nottstu is offline nottstu  United Kingdom
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All really helpful, thanks very much for such a full reply.
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