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Sony CDP-950 Mods - NOS mod produces a lot of noise when CD not playing
Sony CDP-950 Mods - NOS mod produces a lot of noise when CD not playing
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Old 18th April 2019, 07:35 PM   #21
ianp is offline ianp  United States
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Old 18th April 2019, 09:30 PM   #22
dreamth is offline dreamth  Romania
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I think i know a better mod for this player, which is actually NO NOS mod, but a smart attitude about this player so that you get the best sound with minimal intervention.
Keep in mind that This player has a very similar platform as the cd750 and the same chipset as Nakamichi cdp-2e which is highly sought after.I will tell you to do the same as in CDP-750 that i have and shown here:
Best way to mod cheap cd-players-enhancing the noise
Just ignore the comments as that was an early trial within a different setup and with different op-amp as i/v)(lm4562-failed!)

JUST do this:

1.Modify the decoupling capacitors for the MSB...LSB as described by this guy:

Building the ultimate NOS DAC using TDA1541A
Better ask him the exact values for every bit cause i can't find the post where he mentioned it.I just made it a bit bigger, like 1uf/470nf/220nf...


2.Configure the i/v stage approximately as in cdp227es which means that you'll be loosing 1vRMS. That is NO problem, on the contrary, 2V RMS is way too much and it will help with the rest of the mods.

Just bear in mind that ALL the classic players ignored one simple measure which is described in AD797 datasheet which is to add 100 ohms in series with the output of I/V stage before the feedback filter, between pins 1/7 and r404 and r504.That does A LOT!


3.Add a 10k resistor from the output of that resistor to ground.
After R404 and R504(2k7) add some 1n...3.9 nf capacitance to ground, preferably FKP Wima or other good capacitor.


4.Replace the i/v opamps with LM6172.
5.Remove completely the active filter and ground pin 3/5 of that section in each op amp unless you really know what to do with the remaining op-amp.

I also removed the deemphasis network(i like more highs and muting transistors but that depend on their quality.I just don't care about the noise between tracks.Some players don't have any noise by default.
If you're using headphones, Replace CPC450 and CPC550 with a suitable feedback divider if you have high impedance headphones and the volume is not enough,remove the 33k/18k divider and replace the 33k with 1k...3k3.Add 220pf...1nF from the 10k pot tap to the ground .
If you're able to replace the njm4556 (headphones op-amp)with njm2043 or lm4562 you can use that as a variable line output.




Just double the capacitors with Panasonic FC or better ,as in my photos, unless they are dried.
Enjoy your very fast i/v converter with an equal fast amplifier or headphones amp like tpa6120 !
Don't worry about the NOS guys.They are wrong.I am right!
Attached Images
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File Type: png ad797iv2.png (105.4 KB, 24 views)

Last edited by dreamth; 18th April 2019 at 09:40 PM.
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