Sony CDP950 Tweaking Problem with XO clock upgrade - diyAudio
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Old 11th January 2013, 09:08 PM   #1
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Default Sony CDP950 Tweaking Problem with XO clock upgrade

Hi everybody!

Sorry to bother you guys with my lame thread. I am new around and would like some advice in order to try to adress my issue.
I have successfully conducted a very satisfying upgrade of my father's old CDP950 after having read Fikus (the Polish Mad Professor) blog for quite some time.

So far I've replaced all caps mainly with OsCon SEPC (I found them to have the best sound), PSU Caps with KA Nichicons, Diodes with old cascading Vishays for smooth response, changed the Voltage regulators for brand new ones, and bypassed all output resistor network to go directly to the RCA from the Opamp output (upgraded too) through Roderstein blue axial 47uF. Of course I have also switched the crapy ceramic around the DAC for 5 pairs of 220nF+1 pair of 470nF+1 pair of Tantal 2.2 uF ( la Fikus...mind the polarity of these two last ones, Plus sign must be farther from DAC on BOTH sides otherwise you'll hear something is wrong!!)...

Here's some pics of the (partialy) finished project

IMG_0865.jpg
IMG_0870.jpg
IMG_0864.jpg

The resulting sound is already AMAZING and VERY improved compared to the original player, with all subective parameters moving from a very dull sound to a super dynamic and very spacialized Hi End sound. Cool!

BUT I have bumped into an issue trying to upgrade the clock. I have bought a chinese low jitter clock with the correct frequency of 16.9344 MHz. I have connected the board to a 5V direct from Voltage regulator (to the board plus input) and Ground Output to player ground. I have successfully measured the target frequency on the output connection. I know this is not a long term solution, I will build a dedicated Regulator for this card at 8VDC, but I wanted to conduct some tests.

IMG_0873.jpg

In order to implement this low jitter clock, I have removed the stock Quartz, and both caps (18pf) from the board. So basically I should have been just able to get the CD working just by connecting the new clock to one both holes, more or less. Well neither worked for me. I have tried to get some documentation but haven't been able to find a proper way to connect the clock board.

The problem comes from the fact that I have two ICs to clock, the CXD1088 (Digital filter) on which both sides of the stock Quartz are connected (pins 27 for XIN and 26 for XOUT) but WITHOUT a parallel resistor (as stated in most installation manuals), AND the CXD1125 (DSP) through a serial resistor of 1K (R524) (on pin 53 XTAI of the DSP).

I have tried every possible configuration for wiring the clock, bringing the clock signal to both XIN, XOUT, either sides of the serial resistor (R524), adding a parallel resistor of 470 Ohms... none solution seems to work. So I have tried to use my brain a little.

CDP950.jpg

It comes to my mind that the CXD1125 is fed a clock signal from the XOUT pin of the CXD1088. This means that both XIN of CXD1088 and XTAI of CXD1125 are in opposing phase and there is no way that I can connect to both XIN and XTAI with the same clock, except if I put an inverter of some kind between XIN and XOUT of the CXD1088.

What puzzles me is that according to what I've read so far on the Internet, nobody seems to have had similar difficulties mounting this type of clock, but from what I understand by reading the Sony technical drawing, it is not as straightforward as I would have hoped on this particular Sony player.

Am I missing something here or is there really a trick to get both ICs clocked properly?

I would appreciate if someone could put me in the right direction to find a proper wiring.

Thanks guys, any comment would be much appreciated!!

Phil
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Old 12th January 2013, 12:48 PM   #2
oshifis is offline oshifis  Hungary
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The new clock signal should go to the Digital Filter CXD1088 XIN pin 27. The XOUT signal feeds the DSP through the 1k resistor. There is an inverter internally between pin 27 and pin 26. Only the capacitors should be removed (as you did). Use a twisted wire and connect the GND close to XIN. I would not connect the GND at the power input terminal since might cause a ground loop.

Edit: Tantalum capacitors are very poor for audio. Also the upper two capacitos can be the same value. I recommend 470nF also for the MSB.

Last edited by oshifis; 12th January 2013 at 12:53 PM.
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Old 12th January 2013, 01:13 PM   #3
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Hey dear Oshifis !

THANKS a million for your advice!!!

This really help!!! Ok so I start to understand. The problem I had came from poor cabling only. I will try again with proper voltage and PSU for the clock board, will leave the ground as close as possible to XIN and will use twisted pair for clock/ground.

About the tantalum, I believe you, but Fikus states rather differently along with Arcam player implementation for this specific pair of coupling caps. I will give a try to your suggestion anyway!!

THANKS!!!!!!!!!!!!!!
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Old 12th January 2013, 01:50 PM   #4
oshifis is offline oshifis  Hungary
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Quote:
Originally Posted by lefuneste View Post
...will leave the ground as close as possible to XIN and will use twisted pair for clock/ground.
Pin 28 seems the best for this purpose I am a big fan of the TDA1541A so I am very interested in your results. Have you considered replacing your DAC chip from TDA1541 to the A version?

About the tantalum: just knock it with the grip of a screwdriver, and you'll hear the difference They are microphonic like hell...

Last edited by oshifis; 12th January 2013 at 01:53 PM.
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Old 12th January 2013, 04:23 PM   #5
dacen is offline dacen  Norway
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oshifis
I am certain that you mean Pin 27 on the DF as you mentioned in the earlier post. At least that is my opinion as well.
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Old 12th January 2013, 07:11 PM   #6
oshifis is offline oshifis  Hungary
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I mean pin 27 XO input, pin 28 GND. Sorry for the confusion.
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Old 12th January 2013, 08:59 PM   #7
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As a mater of fact Oshifis, I have ordered a used TDA A version in China yesterday evening as I plan to do the NOS modification as well. Let's hope its not a fake one... I'll see how it works out to do just a straight switch first from my stock non A TDA (Fikus' favorite apparently). I will also change oscillator cap for a silver mica which is on its way. These mods won't bring much but just for the principle I'll give them a try.

I am mainly waiting for new opamps at the moment, but due to a postal employee stealing my parcels (6 since September), I have been waiting for the last 3 months to get these damned opamps (dual OP627AU, Dual AD797BR & OP2604AP). For the moment I am still using stock opamps 5532 which are rather not "up to date"

By the way, I have seen on the Sony tech doc that there is an EMPHASIS stage in parallel of the opamps. This stage is "switchable" but I don't have such an option neither on the remote control nor on the player itself. It's really a mystery.

I would like to remove as many as possible useless gimmicks. Any idea what I should remove here as some resistors in parallel are necessary for the opamps operation? I have spent the last 3 days looking for an explanation of such a stage but I couldn't even start to find an answer. This stage seems driven by several cascading transistors and seems to act on the opamps.

It looks really pathetic and I doubt that it's necessary to have 3 transistors there, not mentioning the power consumption that I'd rather give to the TDA...

Emphasis.jpg

Any clue what this stage does?

Last edited by lefuneste; 12th January 2013 at 09:23 PM.
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Old 13th January 2013, 11:34 AM   #8
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http://wiki.hydrogenaudio.org/index.php?title=Pre-emphasis#Pre-emphasis_on_audio_CD

Extra filter comprising R501, C508 and C509, is switched in by Q500. R521 and R502 maintain correct DC conditions. Q520 and Q522 switch on Q500. A bit complicated, but the switching has to be done quickly and smoothly, without injecting noise.

More a blind alley than a gimmick. Are you sure your favourite CD has no pre-emphasis applied? Power consumption isn't a concern. Snip the entire filter and switch if you don't want it.

Muting isn't a gimmick either. I like to insert my own noise between tracks. Music always sounds better in contrast to ten seconds of nails poured into a bucket.
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Old 13th January 2013, 12:14 PM   #9
oshifis is offline oshifis  Hungary
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Phil,

You should check this other thread:

Mod CDP SONY 950

(done the search for you )
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Old 13th January 2013, 03:40 PM   #10
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You guys are incredible!! Many thanks for your replies...

PlasticIsGood, thanks for your help in identifying the useless components, I wasn't sure where to cut between the R500/C507 and the Emphasis stage (R501/R502 and below). Now everything is clearer.
Well actually to answer your question, with more than 6 thousands CD, I had no idea what this pre-emphasis thing was about, but it really reminds me of Dolby B/C NR era and my good old Sony Walkman that I had to carry around with 10 kg of tapes!! Wow almost stone age technology now!! This whole circuit goes down the tube indeed. For the mute stage, it is currently bypassed, but speaking with you makes me think that I may re-enact its usefulness when I move to NOS decoding, switching it on when on pause in order to avoid noise when not decoding (look for NOS hack you'll see what I mean).

Oshifis thanks for the link, I had already checked this thread, but did not look beyond the supercap discussion. Actually I figured the use of this part on my own Ha! But the thread seems longer than I thought, I'll have a look.
For your information, I have just decided to build a discrete JFet output stage as a first step toward lampization. (http://lampizator.eu/LAMPIZATOR/FETI...JFET_CDout.pdf). It seems quite cheap to build and sounds promising. I will order the parts this afternoon. Also I have spent last night deeply checking Caps parameters, and I believe that my choice of same value Nichicon KT series for pre Voltage Reg is wrong as ripple current values are lower than on stock caps (VX) for the + and - 5V. For the -15V I took a KT 50V rated instead of 35V stock, so this compensates and gives me same max ripple tolerance. Still I will try to put better suited caps there.
So I have ordered new high ripple caps with over-sized values for all 3 stages. NCC KY series for the -15V line, will be a 35V 1800uF and Rubycon YXG 25V 5600uF (slightly larger with 18mm diameter instead of 16mm original VX but it should fit right) for the +- 5V lines. It took me quite some time to pin point the best possible caps for sizing, highest possible ripple tolerance and if possible higher capacitance out of what ebay has to offer. Mouser would be too complicated right now for France unfortunately as they have almost everything in stock...
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