| Justcallmedad |
Resume of Sony CDP players mod's “dead” thread.
Dead thread.
I am working around the output stage of a Sony CDP player XB940 SACD, the XA50/30/20 and XB940/920/720 are similar (VC24+ CXD2562Q or CXD8735N - DAC chip’s). I tested various configurations (OP-Amp’s / discrete) the last one uses a trans former to unbalance the output, but it can be used in balance mode. The sound is really very "natural" and the design is quite simple.
The first and easiest way to improve this player is to bypass the “current pulse chips”, so you get the DSD directly from the dac in a differential voltage mode, both at 2.5V dc, I think you have already seen this in a few sites (VSE, LC-Audio etc...) For the output stage, there are various possibilities : Op-Amp, discrete differential to single ended, transformer…
The goal was also to unbalance the dac outputs, to make them compatible with my preamp/crossover or at least to get the choice between balanced or unbalanced outputs.
About the current pulse converters :
Lars Clausen (In another thread) :
“This is SONY's own explanation of the Current Pulse Converter. ...
Sony’s engineers for the "Extremely high Standard" (ES) series created other decisive factors for excellent sound quality: the Current Pulse D/A Converter and R-Core Transformer. Unlike standard D/A converters, the new Current Pulse D/A Converter does not use a voltage-pulse output. Instead it operates with current-pulse output for constant signal quality. Changes in voltage amplitude (e.g. from mains fluctuations) are eliminated and harmonic distortion is minimised. The R-Core Transformer on the other hand ensures a stable voltage supply independent of load. “
My own tests on them :
The current pulse converters are very sensitive to their supply (+7,-7V) and their reference. I tested in this way, after the current pulse converters, with battery power supplies and batteries for the reference, (battery for the reference was the biggest improvement), this modification is not as effective in the reproduce sound quality as the one I describe here, and is more complicated and difficult to implement. Well… I must say that I didn’t test it with a jocko homo I/V converter...
In order to “try” the signal directly at the output of the dac, and to achieve a smooth filtering, the first and simple way, was to use a “good” op amp. The AD826 or AD828 are among the best ones for this application in my knowledge and the less tricky to implement. I prefer the AD828 (Gv>2) but the AD826 with a current sink of 5mA to V-. will give you about the same results. I didn’t tested the most recent ones from Analog Devices…
This simple mod, bypassing the current-chips and a few Burr Brown op amps improved greatly the sound in all the ways !
Here there is the diagram for picking up the balance bit stream output of the Vc24+ at the input of the “current pulse converters”. Thanks Elso, Ergo, Christer for the thread and VSE for diagram.
About the same subject :
Christer’s thread.
Out-picking.
For the output VC24+ output resistors I choose a rather high value 39 kohms. I tested 4,7k, 10k, 22k, 33k, 39k, It’s seems that high values (> 30 kohms) sound best. Difficult to say more, without the schematic of the VC24+… But now than the global design is defined I will do more accurate listening tests on it.
My first “evaluation designs :
XB-output1.
The DAC output offset between +out and –out, is not 0V but a few mV, and moreover, change according to the playing mode CD (pcm) or SACD (bit stream).
So in this second schematic I implemented a dc-servo.
XB-output2.
Extremely satisfied by these firsts improvements, I went further and carried out a very simple circuit based on fet followers.
Fet evaluation schematic.
The sound was astonishing real, natural, when you reach this degree of transparency, sometimes in some cd’s you wonder whether certain noises come from ! Your room ? Are they recorded ? Until you listen the track once more…
Following these encouraging results I refined the design to make it reliable in the player, now it includes a dc-servo. and a transformer.
Fet with dc-servo.
Fet final schematic.
Fet final schematic xfr-less.
The version I prefer, is the fet one with servo and transformer, the op amp version is not very far in terms of "very very good reproduction", but the last fet version with transformer is simply real, well... much more real.
Actually I use the transformer, to unbalance the output (my crossover input is unbalanced). I tested the schematic below, with just one "leg" the +output, and I increase R101/110 to about 390 Ohms to get 0V dc in the output. It's just a very little better than the transfo version, but unfortunately a little bit noisy, well i can hear it with my ears near the horn of my TAD's (of course, noise is cancelled in the balanced mode).
Noise in my 20 kHz FFT is at -114 dB in CD mode and balanced, about -130 dB in SACD mode.
Fet's are matched by pairs and about 9 mA of Idss.
Transfos are LUNDAHL LL5402, because I have 2 of them from an unused audio distribution amplifier, and their characteristics seems to match my requirements. I will test next days an LL7902.
I am not very qualified in transformers : brands… , low/high “copper”, amorphous… etc… Jensen’s and Lundahl seems to be good devices, as they are rather expensive I can’t make a lot of tests, so some advises are welcome.
The output impedance of the fet followers is about 30 ohms, but it's better not to load them at less than 3 kOhms.
For these first evaluations I used batteries.
I tested rather quickly an emitter and a source follower power supply (capacitor multiplying) after a schottky rectifier and an RCRC network, it seems not to be far from batteries, but I need more listening tests to go further. I will work on it after building the output stage on a pcb, and having chosen the right transformer.
I am trying too, a discrete differential input, differential/single ended output, to solve the noise and in a lesser way the filtering (in the single ended mode), as well as to get rid of the transformer. But it is for in a few weeks, for now I will continue to improve and complete this fet design, and use it later as reference.
Elso :
“Many things could be done to improve the Sony: powersupply, bypassing, other opamps etc. etc. The many SMD parts discourage me from doing it…”
Yes I know… But the modification is worth the sorrow! And with a dedicated pcb, just 8 wires from the dac…
Useful links :
Toshiba FET’s.
LUNDAHL transformers.
JENSEN transformers.
Analog Devices datasheets.
By the way… Have a look to the AD826/828 simplified diagrams VAS, output… |
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| EUVL |
Richard,
Great effort, useful information. Many thanks !!
A few pictures would make the thread even more perfect. : )
Keep it up,
Patrick |
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| pro |
Hi Richard,
in the photo the output tranny of my XB720. They directly couple the dac to RCA, just with 8 68hom resistors and a 1.6n cap.
You can also see the Tent's clock and the discrete regulator for the dac. Dac and clock both has their own PS and regulator.
The sound of this CDP is very good, bur actually I prefer the sound of a Teac VRDS8 with a discrete fet IV and output stage, and Kwak's clock. Much more impressive, expecially in the bass side, but anyway the Sony in his price class is really a very well sounding CDP.
Ciao. |
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| ergo |
To prove that I'm not in hibernation either ;)
My Sony CDP-XB930
Ergo
PS. There are some real breaktrough I have made but it'll be for a week or so and then I'll get my own web iste up and I will explain.... |
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| EUVL |
I saw a Tent Clock and 2 Borbely Buffers, right ?
Battery powered ??
Patrick |
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| ergo |
| quote: | Originally posted by EUVL
I saw a Tent Clock and 2 Borbely Buffers, right ?
Battery powered ??
Patrick |
No, the power for Borbely buffers comes from the original PS. This is a point that needs addiotional tweaking.
The breakthrough is related to combination of CDP-XB930 and Behringer DCX2496 digital crossover. Part of it can be seen in the upper left corner of the pic. |
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| Justcallmedad |
Hi, Michele,
Can you specify the type of transformer, its
wiring, caracteristics-datasheet ?
Wich is the load value you use in the secondary ? Volume pot, input stage ?
Wich ratio is the transformer ?
I recovered an old "Elektor" PCM63 converter, with which I would like to carry out some tests. I will be interested in having a look at your I/V converter, for later, when I will finished this project , so if you can say some more …
Thanks. |
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| rbroer |
Good stuff Richard. :)
Keep the updates coming :cool: |
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| Justcallmedad |
I am looking for a test disc, CD and SACD layers, with sine waves at various frequencies and levels, if possible from 0 dBFS to –60 –80 dBFS and silence. I need it to measure and tune the circuit as well as I could.
I have just a "CD test disc" with 1kHz tone at -16 db. I recorded a few years ago a "complete CD test with a digital generator but unfortunately the XB940 doesn't play the CD'R !
I try a Google search ... Nothing in SACD, except some papers from Philips and Sony, both without sales mode indication, and going back to a few years.
If someone knows an easy way to get them... or others !
This W.E. I hope! I will work on the pcb with a complete set of outputs :
Xfr-Balanced, Xfr-Unbalanced, and Fet-direct-Out-Balanced at 0V-dc.
For the transformerless unbalanced circuit, I must design a completely new circuit, it will be for later... |
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| rha61 |
Hi Richard
in your first evaluation , why do you bias the AD826 (5mA) and not the AD828
Was it after listening ?
alain |
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| Justcallmedad |
Hi, Alain,
This circuit was just intended to test the VC24+ output, bypassing the current pulse chips, it was the easiest way to do it, I tested the AD826 with and without the current source a few times, and yes there is an improvement. When I tested the AD828 I tested first without the J511 current source, and the sound was the same as the AD826 with the J511, I tried the 828 + the current source and I didn’t notice a real change. As it was not really better, just a little less noisy (2dB) on the test bench, I didn’t went further, or intended more listenings, because I had already in mind the fet design. If the fet design had not been so promising, I would be turned over on this circuit, and carried out more tests, particularly on this point, it is always necessary to repeat the listenings and to be sure of all contacts of my "wishboard" to confirm the improvements.
If I have time soon I will re-test this point, and hold you informed.
These 2 devices are very close, they differ at first sight by their voltage noise and the compensation capacitor, “Cf” on the simplified datasheet diagram.
However you can carry out these tests, just a J511 or a fet device (3/5mA Idss) between the output and V-. For the AD828 devices be careful in supply bypassing and ground connections, they are prone to oscillations.
Nothing! about the SACD test disc ? Post #10 |
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| futiboho |
| could you please advise where I can get the original full schematic of the XB940 in order to start with the recommended modifications??? |
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| Justcallmedad |
I am working around the power supply for this circuit, the problem is to find the best way to build a suitable one from the existing Sony transformer, I would like an RCRC or LCRC filtering before “reg” but the lack of voltage at the existing transformer 2*13V RMS is not enough for this , maybe a voltage doubler, or changing the transformer, I will work on these various possibilities next days, another possibility would be to install batteries with a simple charger circuit… Patrick => ;-)
I hope scanning soon the XB940 schematics… |
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| Elso Kwak |
| quote: | Originally posted by Justcallmedad
I am working around the power supply for this circuit, the problem is to find the best way to build a suitable one from the existing Sony transformer, I would like an RCRC or LCRC filtering before “reg” but the lack of voltage at the existing transformer 2*13V RMS is not enough for this , maybe a voltage doubler, or changing the transformer, I will work on these various possibilities next days, another possibility would be to install batteries with a simple charger circuit… Patrick => ;-)
I hope scanning soon the XB940 schematics… |
Hi Justcallmedad,
A CLC filter has neglectable voltage drop. No need to scan the maual as I have sent a complete manual as PDF file to futiboho.
:cool: |
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| Justcallmedad |
Hi, Elso,
Thanks for the pdf’s, it will be interesting that you attached them in this thread, that could be useful for people interested by this mod.
The LCRC or RCRC is for me the solution to avoid transient current spikes on the transformer, rectifiers, and 1st capacitor, so less noise (wideband noise), very difficult to remove it afterwards.
Of course the L after C helps a lot, but is it enough ? Once you have ”wideband noise” difficult to remove, no ?
Maybe I am wrong, or more precisely, maybe there is no difference in listening, did you tested this (CLC vs. LC or RC) ?
P.S. I liked very much your KISS project ! :cheerful: |
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| Elso Kwak |
| quote: | Originally posted by Justcallmedad
Hi, Elso,
Thanks for the pdf’s, it will be interesting that you attached them in this thread, that could be useful for people interested by this mod. |
That file is 7MB big so impossible to post here on the forum| quote: |
The LCRC or RCRC is for me the solution to avoid transient current spikes on the transformer, rectifiers, and 1st capacitor, so less noise (wideband noise), very difficult to remove it afterwards.
Of course the L after C helps a lot, but is it enough ? Once you have ”wideband noise” difficult to remove, no ?
Maybe I am wrong, or more precisely, maybe there is no difference in listening, did you tested this (CLC vs. LC or RC) ?
P.S. I liked very much your KISS project ! :cheerful: |
Though the transformer, rectifier and filter caps look like a simple circuit at first glance I am amazed every day how it can be inproved.
I tried a 10 Ohm resistor in series with the choke of the PI-filter in my DAC and it robbed the dynamics form the music.
Then I installed the 10-Ohm between the secondaries and the bridge rectifier and this had the same effect on me.
Interestingly a 1-Ohm resitor at this position is giving less "glare".
The type of transformer and wattage also seem to be important as a toroid has a wide bandwith passing crud (hash) from the mains into your circuit and vice versa. I tried an Amplimo 30 Watt and a Era 30 Watt dual bobbin type and the Era clearly won.
www.amplimo.com
www.era.de
An interestin article in the Audio Amateur pointed me to that.
I also experimented a lot with line filters, including the one advocated by Jon Rish. I could NOT corrobate his findings.
(Ultra)soft recovery diodes also help.
:cool: |
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| Justcallmedad |
Could you give some more details on your DAC power supply, L/C values, type of regulation (or not) after the Pi filter, choke resistance , did you tried soft recovery vs. schottky ?
Which ultra-soft recovery rectifiers did you use ?
Is it something like your clock7 supply ?
At the light of yours tests, maybe that would mean that this is not the inrush current in the first C that puts the "mess" on the audio, but rather the incoming “noise”, or as you pointed out, the out coming one !
I must say that if I can get good results with CLC and the Sony transformer, it will be the easier and cheapest way to go!
I will carry out some tests on it, this w.e., so the more ideas, the more results to understand what happens.
Have you mod an XB940 ? |
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| Elso Kwak |
| quote: | Originally posted by Justcallmedad
Could you give some more details on your DAC power supply, L/C values, type of regulation (or not) after the Pi filter, choke resistance , did you tried soft recovery vs. schottky ?
Which ultra-soft recovery rectifiers did you use ?
Is it something like your clock7 supply ?
At the light of yours tests, maybe that would mean that this is not the inrush current in the first C that puts the "mess" on the audio, but rather the incoming “noise”, or as you pointed out, the out coming one !
I must say that if I can get good results with CLC and the Sony transformer, it will be the easier and cheapest way to go!
I will carry out some tests on it, this w.e., so the more ideas, the more results to understand what happens.
Have you mod an XB940 ? |
Most answers can be found in this thread "high speed diodes" started by Fred.
http://www.diyaudio.com/forums/show...2539&highlight=
I never modded a Sony XB940.
My clock supplies are different from analog supplies used for linestages, DAC-IV-converters and for the TDA1543 I designed a special supply.
It's all on this forum. Press the lousy searchengine!:cool: |
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| Elso Kwak |
Hi,
I found back the Audio Amateur article showing a bandwidth graph for the Avel-Lindberg D-3022 toroid flat to nearly 200kHz and a Magnatek FD7-36 nearly 35dB down at that frequency. Please see Audio Amateur volume 4, 1995, page 36. It's the fourth article about the Jung regulator by Gary Galo. :cool: |
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| EUVL |
Elso,
What are your experiences with batteries as power supply ?
How do they compare with transformers ?
Patrick
PS Would be very grateful if you could send me a copy of the complete manual as well (ybpkwan@web.de). Many thanks. |
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| Elso Kwak |
| quote: | Originally posted by EUVL
Elso,
What are your experiences with batteries as power supply ?
How do they compare with transformers ?
Patrick
PS Would be very grateful if you could send me a copy of the complete manual as well (ybpkwan@web.de). Many thanks. |
I did experiments with batteries several times and posted the results on the Audio Asylum. Please do a search over there, AA has an excellent searchengine.
My experience is that batteries kill the dynamics of the music making it flat sounding. As an added "benefit" batteries always seems to go dead in the weekend when shops are closed.
Shall I propose that other forum members email you the manual as I have a pretty slow connection to the internet and sending the 7MB file takes 45 minutes for me.
:bawling: |
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| Pan2 |
Elso,
you know they have invented these rechargable thingys made of lead and stuff? ;).
Seriously though, did you find the lack of dynamics being the case even when batteries were bypassed with decent capacitance?
/Peter |
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| Justcallmedad |
Power supply first tests and listening…
I experiment quite a lot on the power supply… More precisely on a power supply for the output stage described in this thread and within the accuracy of my sound system. All the following comments on the settings and tunings apply on the power supply for this circuit within the XB940.
1) Transformer : I begun the test with a classic common toroidal transformer 2*12V no brand on it, the goal was to compare batteries to a power supply, and progressively tuning it to a battery level, keeping in mind to use later the sony “EI-analog” transformer.
2) Rectifiers : One of the most important parameters, I tried schottky, fast, ultrafast, soft recovery… After trying more than a dozen of them, what seems the most relevant to sound quality is the soft recovery and speed parameters, maybe the ta/tb in the trr. Schottky are not the best ones, like I thought, or even the amplitude of the reverse current. The ringing characteristic (frequency-amplitude) degrades considerably the quality. The best ones are the BYV27, MBR1100, RURD460, the last one sounded the best. I must say that the BYV27 are not bad, but depends enormously on the brand the batch… Philips are the best ones for this reference. Trying snubbers don’t solve the problem very much, and sometimes worse it. BTW if someone has an idea for SMD rectifier parts… I tried ES1D, BYG22D, MURS120T3, not so good performers as the preceding ones.
3) RC LC LCLC LCRC etc…: After various tests a simply RC sounds the best or almost equal to an LC filtering, in the best case L brings nothing more. ( I tried small L about 2.2mH DCR=0.5R.)
4) Active filtering : To achieve a final good filtering, and more specially noise filtering, I use a Mosfet “capacitor multiplier”.
The ground scheme is extremely important, maybe more, than the devices types or brands themselves and even the circuit. (Star ground / Decoupling caps position.)
In short:
Fast, ultra fast, hyper fast, soft recovery characteristic for rectifiers.
RC filtering, small R, 2 to 10R for followers preamplifiers (small currents/ class A)
Active filtering of noise. Ferrite beads sometimes well placed can help a lot… On this point maybe Charles Hansen or Jocko Homo could tell us more about the efficiency of ferrites over time?
This circuit doesn’t need an accurate regulation, the power supply must be stable and noiseless, that’s all.
The output is about a couple of volts lower than the input voltage (Essentially Vgs).
The second schematic use a TL431, for an adjustable V output.
After trying various designs, here the power supply schematics tuned by listening :
XB-940PS.
XB-940PS_Adj.
Ground scheme is quite difficult to optimize on this player and appears to be important on sound quality (air, emotion, softness) so as the pcb is not easy to modify, as just as ground wiring between pcboards, I wonder whether I will go for a floating output (no reference to player ground on the output stage). Just keep common ground for Clock and DAC, as the outputs are balanced… Just a little modification on the fet’s followers circuit… |
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| Justcallmedad |
What I felt about the ground layout and the ground distribution among the differents pcboards was right, so as it appears to me impossible to optimize the whole player on this point, It will take so much time to tune the ground distribution, listen, mod, listen, measure etc… taking off each time the pcboard modify it, re_putting it on the player, you see…
So, unless remaking all the pcboards, the solution, which not only solves the problem but moreover constitutes a very clear improvement, is to go to a floating mode at the output of the VC24+.
I tried this today and wow!!! The improvement is in the same order of magnitude than bypassing the current pulse converters. For those who have done it, they know what I mean.
I will post later the modifications to carry out on the output stage and power supply.
To test this mod I used the analog power supply trafo for the clock (like Sony did, but with my "reg" circuit:TL431/Mosfet).
To avoid common ground with the player, the easiest solution to test this mod was to re_use batteries, I don’t think the improvement is due to them, taking into account the tests carried out before, on the power supplies (no difference between them).
If I want to use the Sony analog trafo for the ouput stage, I must use the digital trafo (DAC supply) for the clock too, so ??? Maybe with a good supply circuit, it will be o.k. I’ll test this, tomorrow I hope.
If the results are not good, I will go for another trafo just for the clock.
M. Kohjin Yamada, find this link about the SACD test discs, many thanks.
Philips SACD test disc.
I need help on a TDS820 Tektronix scope, the model is discontinued and they don’t repair it any more, if someone in the forum can give me some advises or is related to Tektronix… The problem is in the VCO of the acquisition card, for some special measuring this model is very useful (6/8 Ghz). |
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| macboy |
| I believe someone asked about the service manual in pdf form. Download it from Sony here (7.00 MB PDF). As with all Sony service manuals, it includes block diagrams, schematics, parts lists, disassembly instructions, signal waveforms, etc. |
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| Cobra2 |
Where can you register to get access to other manuals..?
Arne K |
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| Elso Kwak |
| quote: | Originally posted by Pan
Elso,
you know they have invented these rechargable thingys made of lead and stuff? ;).
Seriously though, did you find the lack of dynamics being the case even when batteries were bypassed with decent capacitance?
/Peter |
Yes I also tried Nicads. Caps do not help much.
:bawling: |
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| EUVL |
> So, unless remaking all the pcboards, the solution, which not only solves the problem but moreover constitutes a very clear improvement, is to go to a floating mode at the output of the VC24+.
Richard,
Thank you again for the many useful information you are posting. I do not quite get what you mean though with flaoting the output of the VC24. Maybe I just wait for your final modification instructions. ;)
Patrick |
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| Justcallmedad |
Hi, macboy,
Many many thanks, a lot of people here will be very happy with your XB940 pdf schematics, me the first! I have paper copied this manual at least 6 times!
Hi, Patrick,
What I mean by floating output is to not reference to ground, the balanced outputs of the VC24+ (just get the common mode), because between the ground and the audio outputs +/- of this DAC appears out, unwanted “noises” (power supplies, clock, digital and RF signals) who interferes on the audio signal, the only way to get rid of this, is a perfect ground or not ground at all.
As it appears really very boring, difficult and fastidious to redraw all the ground scheme of this player unless redesigning all the pcboards, the easiest way, is to not use the player ground.
The solution in my design (audio-trafo output) is to reference the input fet’s at half the power supply by a resistor dividing network between V+ and V-, and connecting this power supply middle point to the gates of the input fet’s with 2 high value resistors (1 MEG). Of course the power supply is not connected to the player ground, for this, I use the analog-trafo of the player, providing a few mod’s, with a schematic it will be clearer, I’ll post it soon. (c.f. below)
Tested this last days:
- Digital trafo for DAC and Clock. One reg per “function” (no difference with a complete separate supply just for the clock! Even with batteries//capacitor, curious ???
- Analog power supply trafo for output stage (with no common ground with the player).
Always as good as on my last post, and same quality, with my power supply, but now that I have increased the “resolution” by just using common mode, I can hear a very little difference on batteries vs. my reg power supply on the analog output stage, it’s a little better (more involved, more on the stage with the musicians), with batteries. I will try to improve that the next days…
Updated schematics, when I end up with the analog power supply. |
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| EUVL |
Elso,
I remember you mentioning in one of the threads (can't find it now) that there are two clocks that need synchronising in a typical Sony, at 45mHz and 16.9 MHz. And you mentioned the Swoboda clock.
I had a look at the schematics of the XB940 yesterday (Thanks Richard), and saw 2 clocks at 45mHz, 27MHz and 12.5MHz, but they don't seems to be synchronised in any way.
Would you be kind enough to shred some light on the topic ?
Thanks,
Patrick |
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| Elso Kwak |
| quote: | Originally posted by EUVL
Elso,
I remember you mentioning in one of the threads (can't find it now) that there are two clocks that need synchronising in a typical Sony, at 45mHz and 16.9 MHz. And you mentioned the Swoboda clock.
I had a look at the schematics of the XB940 yesterday (Thanks Richard), and saw 2 clocks at 45mHz, 27MHz and 12.5MHz, but they don't seems to be synchronised in any way.
Would you be kind enough to shred some light on the topic ?
Thanks,
Patrick |
Hi Patrick,
There is a non-synchronised 45.1584MHz clock at the digital filter/DA converter (IC301)
There is a 27 MHz clock at the servo digital signal processor (IC607), also not synchronised.
The 12.5 MHz clock is for the system controller.
In my opinion it is worthwhile to replace the 45.1584 and 27 MHz clocs for sound improvement.
My comment about the synchronised clocks was for much older Sony models.
Please contact me by email for a working solution with my clock at these frequencies. |
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| EUVL |
> Please contact me by email for a working solution with my clock at these frequencies.
Elso,
Many thanks for the reply.
I already have a copy of your 45MHz version, so I guess I only need the 27MHz one. Am on business trip (in Eindhoven) so it won't be a few days. But surely will get in touch.
Cheers,
Patrick |
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| EUVL |
One year on, it is finally finished. Thanks to Richard for his insirations and motivations.
Sounds great to my ears (reference Meridian 508-24). No plans for further changes, at least for some time.
Great value for money at less than 500 Euros, including a second hand player from Ebay.
Patrick |
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| EUVL |
| With clock and buffer / filter removed. |
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| EUVL |
The modified PSU for the VC24+ on the Audio Board.
(CRC -- LM317 at 5.2V -- RC, plus Wenzel noise cancelation circuit at the Audio Board) |
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| EUVL |
The Perez buffer at 9mA bias, with a different filter (3rd order 100kHz passive). Dual mono, separate PSU's (current sourced discrete shunt regulators, +/- 15V). Balanced output.
Clock is Tent (gift from Richard with sincere thanks, otherwise no other reason), 8.4V NiMH battery powered with a separate current sourced shunt regulator in between. House in separate nickel plated aluminium housing (top left hand side).
Signal cables from DAC teflon twinax 75 ohm shielded, from clock 50 ohm telfon coax. |
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| av-trouvaille |
Hello,
Compliments, your modifications sure looks professional.
I'm about to install the Tent-clock in my XB940 and I read about this nice thread. Would you be willing to pass information on the output section that you've made? Or may be you would even have a spare set of pcb's left?
If you want to respond off-list you can mail me at: vrhff04_at_xs4all.nl (please replace _at_ by @).
Best regards, Arjen. |
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| av-trouvaille |
Hello Patrick,
In post 37 you write:
The Perez buffer at 9mA bias, with a different filter (3rd order 100kHz passive). Dual mono, separate PSU's (current sourced discrete shunt regulators, +/- 15V). Balanced output.
Would you mind sharing the schematic of the current sourced discrete shunt regulators, +/- 15V?
Best regards, Arjen
you can mail me off list when you prefer:
vrhff04_at_xs4all.nl
NB. please replace _at_ by @ |
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| systemerror909 |
Someone posted this a while ago, a link to sony schematics:
" Post #26
I believe someone asked about the service manual in pdf form. Download it from Sony here (7.00 MB PDF). As with all Sony service manuals, it includes block diagrams, schematics, parts lists, disassembly instructions, signal waveforms, etc."
I am trying the link, but it asks for login, etc and won't let me access anything. Really like to get ahold of some sony manuals, anyone help me out? |
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| trans322 |
I have read Christer's outpicking thread of the VC24+ and Mr. Perez's circuit modifications with great interest. But is there a discrepancy between the two? The outpicking diagram (which illustrates the junction between the DAC and the Current Pulse IC's) shows two tied in pairs.
The first pair: Pin 28 and Pin 25 off the Pulse chip input are tied after the resistors.
The 2nd pair: Pin 27 and Pin 24 are tied after the resistors.
This corresponds to tieing R2(-) and R1(+) together, and R2(+) and R1(-) as another pair.
This illustration (http://www.diyaudio.com/forums/atta...=&postid=255161) differs from the assignment of inputs in Richard's schematics where it is indicated that R1(-) and R1(+) are tied through resistors, and R2(-) and R2(+) are also tied; making the second half of the input.
My question is, which version is correct? Using the Sony service manual, this indicates, for example R1(-) and R1(+) are on pins 24 and 25 of the Current Pulse input.
Any thoughts or comments would be appreciated!
Trans32 |
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| futiboho |
As most of you seem quite experienced with sony xb 940, I would appreciate very much if you could advise on the following noise problem:
After some mods (LC XO Clock, Black gates on the audio board, 2 silver caps at the output and some power supply and ground micro-changes such as grounded copper plates for better separation, etc.) the CDP now operates normally but with very loud high-frequency noice like emergency train brakes or rather a hysterical scream, I guess at about 5-6 kHz.... It seems to me this is a digital noice, although I did not touch the digital board. The noice starts a second after I press play and is much louder (unbearable) than the music, which seems to sound OK.
Please note that earlier test with the clock only (w/o the rest of mods and the clock's own power supply, added later) was ok. I changed the chips, no diffrence, so it is not them.
Another Q: Is it really a good idea to do the LC ZapFilter mod (also hoping it may cure this crazy oscillation???)
Tips will be highly appreciated! |
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| cbachalo |
Has anyone noticed when they bypass the Sony SCD-1 or 777ES S-TACT that it is noisy?
Have you noticed a low level noise during quiet moments of a recording? It sounds like digital hash and a bit like birds chirping. It is quite intrusive with low level recordings or recordings with a lot of quiet like classical. Possibly some IM artifact? Whatever the S-TACT does, it appears to be removing this noise, since I do not hear it out of the stock outputs.
If you have heard this when bypassing the S-TACT, did you find a solution and what was it?
I have found that one channel is slightly noiser than the other which is helping me to pinpoint. I reversed the inputs to the VSE and the noisier channel followed the reversed input, so it is not the VSE causing the problem.
I have connected the outputs of the player directly to headphones and I still hear it, so I don't suspect IM distortion in the downstream components.
I had read somewhere that the VC-24 can get a little noisy when overloaded. Perhaps this is the issue since it is feeding into both my VSE as well as the S-TACT. I may remove the 4 331ohm pads to remove the S-TACT load and see if this solves the problem. Can I do this without impacting the operation of the player, other than disabling the stock outputs for DSD of course?
Do you think this will solve the problem, or will this problem only be solved by the S-TACT?
Thanks. |
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