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Old 8th March 2008, 05:07 AM   #1
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Default Want to bypass opamps in Sony Cd player

As a test DIY project, before I open up my SACD player I've opened up an old Sony 5 disc changer. I want to bypass the opamps, but I'm having a hard time determining which chip is the DAC.

I've got a CXP50116, which appears to control the display on the CD player.

I've got a CXD2500BQ, which might be a DAC, but I can't tell.

I have a CXD2560M (24pins), which I cannot find a datasheet for.

I have one final small chip which the number is rubbed off. It looks like it says "PULSE" and CXD25678 OR CX02567B or something. The number is really difficult to read so I could be way off. It's a 28 pin chip.

All of these are surface mount btw.

Any idea which of these is the DAC, and which pin I can pull L and R audio off of to wire to capacitors and then to two new chassis-mounted RCA jacks? The plan is to use a tube preamp stage between this CD player and my amp.

Thanks!

Charles.
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Old 8th March 2008, 07:39 AM   #2
Mooly is offline Mooly  United Kingdom
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Hi. The 2500 is a digital servo, EFM and error correction processor + a lot more besides, e.g. variable speed playback if machine has that option. You need a circuit diagram ! You can't really just bypass or eliminate opamps, the output from the DAC is TOTALLY unsuitable to feed direct into an amplifier. Further the opamps are usually used to implement a "reconstructive" low pass filter, and without this this the audio signal will be grossly distorted.
Regards Karl
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Old 8th March 2008, 10:03 AM   #3
poynton is offline poynton  United Kingdom
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Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)
I agree ... not a good starting point.

CXD256xx are differential output DACs with noise shaper and are not an easy option even if you find a diagram. Filtering is required.

Try and find an old Marantz or Philips (not bitstream)


Andy
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Old 8th March 2008, 02:14 PM   #4
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Basically I want to replicate the "Swenson Mod" for the SCD-CE595 on this cheaper POS CDP-C27 player. URL here: http://www.head-fi.org/forums/f6/mod...-ce595-206856/

This is basically my practice mod before I open up my SACD player.

Why would this mod work on one DAC but not another?

Thanks.

Charles.
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Old 8th March 2008, 05:12 PM   #5
Mooly is offline Mooly  United Kingdom
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Charles, I don't think you're comparing like for like. Your old Sony almost certainly uses a DAC that provides a current output and this is converted via an OpAmp to a voltage (I/V convertor). All these stages are required. From here there will probably be another OpAmp that is used for implementing the low pass filter. I quickly looked at the link you provided and the first thing mentioned is that this mod is possible because the output from this particular DAC is a voltage source, not current. If you can provide a circuit for the SACD player we might be able to advise better.
Regards Karl
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Old 9th March 2008, 06:45 AM   #6
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Well, if that's the case... I might be more interested in adding an SPDIF output to the old 5 disc changer and using an external DAC.

I guess I just got excited between the SACD player mod and the Playstation mods on this site and decided to see if I could hack this old player as well. Looks impossible, so I guess I'll put it back together and just mod the SACD player.

Charles.
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