Hi everyone
I’ve just got the above CDP for a reasonable price. After studying the design, I came up with some ideas for modification as follows.
1. The analog and digital sections share the same power supply. I plan to insert a new power supply for the digital section with a separate transformer. This is straight forward.
2. The player has 4 dac chip AD1860, two for each channel in parralel. Here I plan to convert the configuration into dual differential. The design utilizes the internal opamp for IV. I am not sure on some points here:
(i) to convert from parallel to dual differential some suggest to invert the data line for one of the two DA chip in each channel and then replace the external analog stage with a pair of line level transformers. IV is already done inside the chips. Does this scheme actually work?
(ii) for the analog stage using 1:1 transformers do I need to terminate the primary or secondary windings? If yes what is the recomended resistor value? I plan to use some Edcor 600:600 that were left over from other project. I think I may need to lower the Vout from dac chip by adding an extra resistor in parallel with the internal resistor of i/v too.
Any comments or suggestions are welcome. I have included part of the schematic.
I’ve just got the above CDP for a reasonable price. After studying the design, I came up with some ideas for modification as follows.
1. The analog and digital sections share the same power supply. I plan to insert a new power supply for the digital section with a separate transformer. This is straight forward.
2. The player has 4 dac chip AD1860, two for each channel in parralel. Here I plan to convert the configuration into dual differential. The design utilizes the internal opamp for IV. I am not sure on some points here:
(i) to convert from parallel to dual differential some suggest to invert the data line for one of the two DA chip in each channel and then replace the external analog stage with a pair of line level transformers. IV is already done inside the chips. Does this scheme actually work?
(ii) for the analog stage using 1:1 transformers do I need to terminate the primary or secondary windings? If yes what is the recomended resistor value? I plan to use some Edcor 600:600 that were left over from other project. I think I may need to lower the Vout from dac chip by adding an extra resistor in parallel with the internal resistor of i/v too.
Any comments or suggestions are welcome. I have included part of the schematic.
Attachments
The No2 will require a dedicated IC, I am not sure how to call it... Denon called it AL24. It is an IC that will provide left channel DATA+ and DATA-, and the right channel DATA+ and DATA- that will feed the dual differential DAC's. But, any similarity with an analog differential terminology should, in fact, be avoided here.
Anyhow, I have attached the schematics for Denon DCD1650R.... have a look🙂
Anyhow, I have attached the schematics for Denon DCD1650R.... have a look🙂
The solution using 74HC04 IC seems to work when I try modelling the inverted data signal.
For example with 4 bit sample size
0000 —>invert—> 1111
0001 —>invert—> 1110
0010 —>invert—> 1101
0011 —>invert—> 1100
...
1111 —>invert—> 0000
For example with 4 bit sample size
0000 —>invert—> 1111
0001 —>invert—> 1110
0010 —>invert—> 1101
0011 —>invert—> 1100
...
1111 —>invert—> 0000
CDP-990 w 4x AD860N-O
I bought one of these locally a couple of months ago (CDP-990 w 4x AD860N-O). It had sat for a while and needed some love (and a used low mileage laser) It is a very nice sounding unit. I am sure I could squeeze a little more out of it with some upgrades (Like caps, etc), but am sure I would mess it up if I tried these mods. Would be curious how this goes though. Good luck! 😎
I bought one of these locally a couple of months ago (CDP-990 w 4x AD860N-O). It had sat for a while and needed some love (and a used low mileage laser) It is a very nice sounding unit. I am sure I could squeeze a little more out of it with some upgrades (Like caps, etc), but am sure I would mess it up if I tried these mods. Would be curious how this goes though. Good luck! 😎
@Dogchow
It’s a decent player but Sony made compromise to cut cost in the power supply.
I like the clocking arrangement of this player. Sony has this CXD8097 chip dedicated to clock management. It feeds clock signal to the dac chip and the digital filter. This should help with lowering jitter.
The analog section run at +/-5v, while they could do it with +/-12v for the opamp including the analog supplies for ad1860 chips.
The digital filter and other digital circuits share the same +5v power supply with the analog section. This is what I plan to mod first i.e. to power it separately.
Changing analog power to +/-12v will involve cutting many pcb traces.
This is mainly for fun since a Denon dcd-1650az with 4 pcm1704 in dual differential mode can be had for less than 300 bucks
It’s a decent player but Sony made compromise to cut cost in the power supply.
I like the clocking arrangement of this player. Sony has this CXD8097 chip dedicated to clock management. It feeds clock signal to the dac chip and the digital filter. This should help with lowering jitter.
The analog section run at +/-5v, while they could do it with +/-12v for the opamp including the analog supplies for ad1860 chips.
The digital filter and other digital circuits share the same +5v power supply with the analog section. This is what I plan to mod first i.e. to power it separately.
Changing analog power to +/-12v will involve cutting many pcb traces.
This is mainly for fun since a Denon dcd-1650az with 4 pcm1704 in dual differential mode can be had for less than 300 bucks
Hello Quan Tran
"It’s a decent player but Sony made compromise to cut cost in the power supply."
I don't disagree. I would love to find a cheap 338 / 557ESD or similar. I will eventually break down and buy one on ebay etc. I think the 4 AD D/A's greatly improve the sound quality over a similar CDP-790 US model. I also have a Arcam CD73 with the Wolfson D/A's which is also bright and happy.
If you can make yours better, I am on board as a spectator. If I tried the engineering you discuss, I would likely start a small fire. I am a good mechanic but no engineer. 😀
"It’s a decent player but Sony made compromise to cut cost in the power supply."
I don't disagree. I would love to find a cheap 338 / 557ESD or similar. I will eventually break down and buy one on ebay etc. I think the 4 AD D/A's greatly improve the sound quality over a similar CDP-790 US model. I also have a Arcam CD73 with the Wolfson D/A's which is also bright and happy.
If you can make yours better, I am on board as a spectator. If I tried the engineering you discuss, I would likely start a small fire. I am a good mechanic but no engineer. 😀
Sure, I will report back the result after implementing the modification. I think the DC coupling cap can be removed as the service manual indicate 0v at the opamp output. I have yet to measure the actual DC level here.
AD1860 has I-out capability, why not install your own I/V stage? Both chips' I-out pins can be paralleled simply by tying them together. I'm not sure going differential/balanced will be a step up.
The analog section of this player is quite ok with two RC5532DD opamp for filtering and buffering. Filter caps are good quality. The output coupling caps were suitably chosen by sony. I tried to replace them with blackgate FK which only sound brighter but not any better than the original so I put back the original Elna Duorex II.
I also tried to replace the ceramic bypass caps with RIFA polypropylene. This also cause the sound brighter so I put back the ceramic caps.
Only the separate power supply for clock section is a REAL significant improvement.
I also tried to replace the ceramic bypass caps with RIFA polypropylene. This also cause the sound brighter so I put back the ceramic caps.
Only the separate power supply for clock section is a REAL significant improvement.