Modding a cheap sony CD player- good results! (long)

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Hey all you crazy modders out there, just thought i'd share my experience...

I bought a cheap sony CDP-212 for $NZ100 (~$US50) because it was a good transport, it would play even the most destroyed CDs without a hitch; and I am a poor student! However, it was a little harsh I thought, with a bit of sibilance on hi-hats and "S" sounds that had me reaching for the tone control on my tube amp (home made of course!)

After reading heaps of NGs and this site (what a great resource!) I went for it and did some hacking around.

The player has two PCBs, the main board directly behind the display and buttons with the audio and control circuitry marked CDP 212-312; and a small board at the rear of the player with transformer, filter caps and RCA jacks.

Stage 1.
The unit used a single flat plastic cable for power and audio connections to the back of the unit- A separate audio cable was added direct from the RCA jacks to the main board. Two SMD resistors were bypassed by this so I shoved a couple of metal film ones in.

The power supply was (hopefully) improved, with more caps added and beefier diodes. I tried schottky diodes but they werent happy and gave me wierd voltage readings. The 7V rail had a 10000uF and a 2000uF across it, this was bypassed with a 0.1uF polyester. The -40V rail had a 100uF across it, this was doubled, and a 0.1uF bypass was added.

Stage 2.
The DAC in this player is a ???2565 or something, the chip has been coated to make it impossible to read. This feeds into two 4558 dual-op-amps (see pic), through a couple of 100uF caps, muting transistors (circled) and then about 5 cm along the PCB to the aforementioned ribbon cable. Most components except the big caps are SMD which is a pain. The muting transistors turned into dust when I tried to unsolder them!

Just for a laugh, I drowned both crystals in a blob of epoxy resin. (Hey they vibrate right?!)

According to the datasheet for the 4558, the outputs are at pin 1 and pin7, which here fed directly into the 100uF cap. After reading 0.05 and 0.02 VDC across these caps, I felt pretty safe in subbing a 0.15uF film cap, which should easily block this level of DC. I connected the other end of the caps directly to the RCA jacks.

The results? A definite improvement for $15 in components. The sibilance is gone, the sound is a lot more "real" but i'm not going to crap on about imaging or anyhting, just that the sound is a little better, more realistic and easy to listen to. Better bass too. I tested it with a bit of Ben Harper at various stages throught the mods, and the last ones made the most difference to the sound. There is a slight click at turn on now, but I leave it on all the time anyway so no worries. All in all, I am quite pleased...

As always, YMMV, and you may fry your machine by trying any of these mods. At one stage I had no sound and I was a little stressed. :D :D
 

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After having my @ss seriously flamed on that peculiar medium that is usenet, I should add:

My 0.15uF DC decoupling caps are too small if your preamp has an input impedance of less than ~50k. It may cause some lossof lower frequencies. A cap of a few uF would be much better. Still I dont see the need for a 100uF, that seems huge!

Also the power supply can probably be left alone: Apparently bypassing the electrolytic caps with a film cap doesnt always shunt the high frequency noise to ground: it may cause some strange oscillation instead yadda yadda yadda. The thing which gets me is some of these guys who said this seemed as clueless as me; you have to wonder whether their urban legend that this is bad is just the same as my urban legend that this is good?!!? :D

I still stand by the claim that this player has a noticeably improved sound.
 
My CD player wants modding too. Never don this before, though.

What do you mean the schottky diodes gave you weird power supply voltages? I would have thought they would be great with their lack of reverse recovery and therefore quietness. Also what is the deal with removing the mute transistors? Are they shunted across the line and therefore add distortion or something?

GP.
 
Shifty:

glad to hear you've taken the plunge and dove right in with both feet! I'm sorry to hear you got a negative response on usenet though... I haven't been on there in years, but not for any particular reason. I do feel that this forum has a much better sense of community though!

You might want to consider replacing the 4558's. I recently modded my Sony DVP-NS500V, and replaced a 4558 opamps with AD8620. Though, I feel you might get more bang for the buck with an OPA2134, especially if you find the sound on the dry side... the OPA part sounds to my ear more musical, lush and full (as if those words can really convey what I hear... heh), whereas the AD part seems to have a slightly dry analytical sound, but is somewhat more transparent. Also, on my 500V, I just shorted the output cap instead of replacing it, with no problems. I suggest the opamp swap first to see what kind of DC offset you're left with, but if it's just a few millivolts, I recommend going DC coupled. There are more details on modding the Sony players here: http://www.diyaudio.com/forums/showthread.php?s=&threadid=3971

Check out the diyaudio wiki, and you'll find my guide to SMD soldering, which I hope will help you deal with those little SMD critters in the future. You might also find out how to read the part number off that DAC ;) which is probably a relabelled AKM part.

Cheers,
 
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