Pointers on upgrading CDP output stage. - diyAudio
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Old 9th February 2008, 08:09 PM   #1
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Default Pointers on upgrading CDP output stage.

As usual I have been sifting through threads for a few days and seem no closer to an answer than when I started. I have a Proton AC 420 CD player that has just joined the family, though very basic (and old) its performance is suprisingly good. The down side is that the trebble is a little unrefined and bass a little lean. Popping the cover has revealed 5 op amps clustered around an oddball Yamaha SLC-A iG-15630 DAC. The OP amps are all JRC's 1x 2068D, 2X 4558D, and 2x 4560D. I have found threads that recomend replacing the 4560D for instance with a Philips NE5532 but have found other threads that consider the 5532 rubbish and instead recomend implementing the OPA 2604. Also as time goes by "great" op amps become "ok", then finally "crap" so I am also looking for some more current recomendations.

Thanks in advance!
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Old 10th February 2008, 07:26 AM   #2
Mooly is offline Mooly  United Kingdom
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Hi, There seem to be a lot of threads about output stages and Opamps at the moment. I am not familiar at all with your player but as for the Op-Amps you might improve the performance, all depends on the rest of the player really. That 2068D that does sound an oldie ? Is it a single or dual inline package ? It's probably used in the servo parts of the circuit rather than audio stages. The 4558 is a dual 741 and the 4560 is, if memory serves correctly similar but with a bit more "umpty" It would drive low impedance loads better. Does it have a headphone socket ? If you want a play, remove the 4558 and 4560 and fit sockets. Try replacing both with TLO72 as these are cheap and suprisingly capable for high quality audio. You wont do any harm, I just wonder about the 4560, it,s extra output capability is there for a reason. Can you tell what it feeds, is it headphones or is it in the servo section. If servo leave it be. If you like what you hear the OPA2604 remains a favorite.
Regards Karl
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Old 10th February 2008, 02:20 PM   #3
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Hi Karl, yep this baby has an output for headphones, I haven't traced the board to figure which set of OPamps drives that output. There certainly are a lot of op amps in there especialy sice the data sheets show at least 4 of them as dual op amps, they are all dual inline packages. I wish I could dig up some info on the DAC, I found like 2 sites that mention it but they are not in english and I couldn't translate. The author of the thread posted a pic of his player a Memorex cd-4000 and it has the identical internals as the Proton AC 420! Well, web hooplah aside my ears enjoy this player very much, stereo separation, imaging and detail are improved over my AMC cd8b, with the nod going to the AMC for smoother highs and deeper bass.
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Old 12th February 2008, 09:55 PM   #4
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An honest correction, not just applying the defribulator to my dying thread. I have a Yamaha ym3020 DAC in the Proton, got confused by my own handwriting. I just wish I could find a proper datasheet for the DAC so I could determine analog out puts for left and right channels, not a very popular DAC unfortunately.
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Old 13th February 2008, 02:28 PM   #5
maxpou is offline maxpou  Canada
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Hi S.Spielbergo,
i make some research on the net i found only this datasheet for your DAC. A TL072 is a good choice, i replaced a 4558 for TL072 and there was a big change, the high are soft and the bass has good attack. good luck! Maxpou
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File Type: pdf ym3020.pdf (80.3 KB, 119 views)
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Old 14th February 2008, 04:55 PM   #6
kevinkr is offline kevinkr  United States
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Try the LM4562, it will happily replace the 4558 and probably the 4560 as well. And it is much more sonically capable imho than the 2604 one of my previous favorites. Look for other possible improvements to the audio path, power supplies, etc.

The LM4562 is available from digikey in both dip and soic packages, currently it is about as close to sota as an audio op-amp gets.
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Old 15th February 2008, 10:43 AM   #7
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I'm going to put in an order with Digikey today, LM4562 and TL072 have made the list along with the venerable NE5532a and two others. Thanks for the suggestions. I'm still trying to map out the board a little so I can see what we have between the DAC output and rca jacks. Anybody know what values are common for the bypass caps just prior to the rca connections, i'd like to give them the heave-ho but all I can find near the rca's are a pair of 4.7uf electrolytics and a few tiny tantulums that I can't read very well.
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Old 15th February 2008, 11:31 AM   #8
Mooly is offline Mooly  United Kingdom
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Good to hear you're having a go. I have not tried the LM4562 myself so can't comment on that, the OPA2604 has a distortion spectrum that is of the "right" type for audio, that is the even harmonics predominate over odd and this can make for a more "musical" sound. The amounts produced are vanishingly small anyway, but the ear does seem to pick up on this. Just as an aside, I used the NE5532 and 5534 some years ago in a rather specialised piece of audio equipment and preamp combined, and the results were dissappointing, very "unmusical" and it was the NE5532/4s . As an engineer I hate it when you can't measure or pin down an effect like this. The prototype used TL072s and sounded wonderful, I broke the golden rule of changing a part without a full evaluation first. Anyway have fun and please let us know how you get on. Oh and change just the Opamps first and do a full listening test before you change any caps etc. Listen over a few days as "experimenter expectation" comes into play here. It's easy to decide that some part or mod WILL be better. Trust your ears and listen to a variety of music.
Karl
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Old 15th February 2008, 01:13 PM   #9
hobbitz is offline hobbitz  Thailand
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I have tried LM4562 and LME49860 and have found that LME49860 sounds better than LM4562.
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Old 15th February 2008, 01:38 PM   #10
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I got the recomendation for the LME49860 just before ordering so it is also on its way (and its just as well, I was below the minimum). I will be soldering in the sockets I grabbed from Radio Shack over the next day or so.I figure whatever IC is my #2 pick will go into the phono stage of my Proton AM 656 integrated amp. Your right though Mooly, its like working on a car you gotta pace yourself with the mods
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