DACs & CAPs (Sony dvp-s7700 tweaking) - diyAudio
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Old 30th January 2007, 08:28 AM   #1
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Location: Bari
Default DACs & CAPs (Sony dvp-s7700 tweaking)

Hallo 'verybodies,
I ve resisted till now to tweaking my Sony DVP-s7700,also because it shows really good expensive component on its audio pcb... But the time as come...

I've just repalced the decoupling cap at the end of the signal track (47Uf SILMIC // polyester 0.2) with a Sprague 10Uf polypropilene rated for 400V ...
I'm always afraid by the cut on the lowest registers introduced by small decoupling caps, I think that I can live without the bass that the sprague have theaft...

Now the problem comes with another electrolytic that people at Sony decide to put beetween the dac (a sony cxd8799-t2) and the first stage of the BB opa2134.... also here there's a 47Uf cap.... I got another pair of that beautyfull SPRAGUE... do you think that at a DAC output a non polar cap can replace a polarized cap?

Also I wonder if anyone can predict how much bass the caps will thief in this position...
Also since that the op-amps present a dual rail supply (+9.3 and -9.4) do You think I can remove the capacitor on the output?

If anyone woul like to halp me to improve the sonic performance of this player I can post here the pics of the schematic and we can work on it togheter this will be helpfull!

Kind regards,

PS Excuse my horrible English!
PPS Anyone know anything about the empirical audio mods on the transport part of the player? I live in Italy and I can't ship to USA this player... ( shipping+ customs duties+ and mod cost will be a too much higher price for the player real value...)
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Old 31st January 2007, 03:43 PM   #2
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You can eliminate the output dc blocking capacitors. They are not necessary in the S7700. I don't recall at the moment if the coupling caps between dac & opamp are needed, but I think that they are, and in my S7000, I replaced them with Nichicon Muse(30 years as a tech, I can tell you that Nichicons are the best & most reliable lytics in the world) caps of the same or somewhat larger value. The best other mod I can recommend is to put at least 470uF of nice(i.e., Nichicon in my eyes) lytic cap on the supply rails directly at the OPA2134 chip pins, paralleled with as large a polystyrene cap as will fit. Also, you can gain some extra clarity by eliminating the series resistors and the muting transistors on the final output lines.
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Old 1st February 2007, 02:31 PM   #3
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Many thanks for Your reply stephen!
I've a pair of question for You...
You say that the coupling caps at the end of the circuit could be completely removed, this happendsince the OP-amps are supplied by a two rail psu?
Do You think is possible replace the caps beetween the DAC and the first op-amp stage with a non polarized one?
If, as I mind, the Sony DAC has on its output an integrated 20Uf capacitance I think that could be fine to replace the electrolitic silmic 47Uf with a polypropilene 10Uf non polar capacitor... The total capacitance given by the series should be slightly modified (respect the original) and will not affect the bass response but I don't know if in this position the circuit need a Polar Capacitor...I'm a bit scared by the difference beetween Polar VS Non-Polar... I really don't want to damage anything...

I've put a big Sprague 10000Uf 80V after the diode bridge in the PSU board, the total capacitance in the Psu is only 235Uf before the regualtors... (since the two SILMIC in series are only 470Uf)... this is really a small value!

I will use a pair of caps on the positive and negative rail on the op-amps: good Idea!
Also I wonder if could be a good idea replace the small diodes of the rectifier...
I search for the component datasheet and i find that these are simple diodes but with little voltage drop on it...
I don't know if upgrade to a fast recovery diodes would really enchance the sound... and if the little voltage drop is important in the psu layout and can't be modified.

Also from the service manual I see that only one is the muting transistor in this model (per channel) it has the drain connected to the signal path and it seem driven by another transistor that recive the command on its gate from the DAC itself... I think that remove it probably could affect the DVD use of the player...
Are you sure the muting transistor could be removed without any consequence?

Many thanks for Your Help!
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Old 1st February 2007, 03:58 PM   #4
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I will have to take a look at my S7000 service manual(same dac setup as the 7700) if I can remember to do that today at my shop, to answer the coupling cap question. I am pretty sure that the dac has positive & negative differential output for each channel, and that each has a dc voltage riding on it, as I think the whole dac chip is single ps. But, if these dc voltages are all equal, which they should be, it may be possible to eliminate the coupling caps to the output stages. This is most likely to be the case, but probably would be necessary to add either an offset voltage trimming circuit or a simple dc servo amp to each output stage. I think this would be quite a jump in sound quality. I will have to try it myself.
The audio section power supply pre & post regulator capacitance should be increased as much as space will permit, I say. And I did install IXYS soft-recovery diodes for rectification, as I always like to do in any audio ps.
On the muting xstor issue, again, I should have a look at the diagram. The main reason I like to eliminate them is to allow elimination of the series resistors. But if you keep at least a ten ohm or so series before the muting, it will negate any miniscule chance of drawing excessive output chip current. I think there is only a small chance that the muting xstors have a negative affect on the sound.
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Old 1st February 2007, 04:29 PM   #5
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I don't need to remove completely the cap after the dac (I will surely remove the ones on the output) I really would like to know if there'is any difference beetween polar and non-polar....
There's any good reason to prefer in this position a polar cap instead of a non polar polypropilene film one?

If You like there's a copy of the 7700 service manual here....
is divided in 4 rar archive for an easier download:


Thank You again
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Old 1st February 2007, 04:35 PM   #6
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I need to get going to the shop, so only have a minute right now.
There is no reason to stay with polarised caps in that position. Non-polar film caps are certainly superior. Non-polar or bipolar electrlytics, though, are usually inferior in sound to polar electrolytics. Which is why we always use film caps where they will physically fit!
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Old 1st February 2007, 04:41 PM   #7
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Thank you stephen...
I haven't too much confidence with the digital domain, also if this is in its analogue output...
Have a nice day...
I think in USA should be early morning... since here is around the 7 pm...
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Old 2nd February 2007, 03:34 AM   #8
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It's been so long since I'd looked inside an S7700, I'd forgotten that the dac chip is a little different than the S7000. Your machine has single ended voltage outputs from the dac, whereas my 7000 has differential current output. Since yours has a dc bias on the single ended dac outputs, you pretty much need to keep the dc blocking caps.
Since the shunt resistor after the cap is a high 330k, I don't think you will lose any audible bass at all with 10uf film caps. Should be perfectly fine & sound great.
I think you might also get some improvement in "blackness" of background(i.e., reducing noise & grunge on power supply lines) by replacing the +/-9v regulator control opamp to an opa2134ua or op275gs.
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Old 2nd February 2007, 07:46 AM   #9
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I've replaced the elctrolityc after the dac with a big polypropilene and remove the output cap the improvement is quite fantastic! Also the PSU op-amp (I'm a bit scared by de-solder it since it's has a SOIC package) will surely changed! And of course the DAC psu caps they are just 47UF I'm think to replace them with a better value ones...(Nichicon Muse of course, but I think will be hard to find them in Italy) Have You give a look at the transistor of muting in the output section? I give a better look at the 7700 layout and I think that the muting ones could be removed but what about these filter transistor beetween the two opamp stage???
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Old 2nd February 2007, 03:43 PM   #10
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I think I ended up with 470uF Nichicon caps on the dac chip's psu pins.
The muting xstor can definitely be eliminated, but I think the filter switching xstor should NOT be eliminated.
On the power supply board, I think I used 4700uf on each line, but then another 2200uf on the AU board, pre-regulator, and at least 2200uf right after the regulators.
Ebay seller "capacitor12" has a giant stock of extremely inexpensive Nichicon caps of many, many varieties, and I am quite sure he will ship overseas.
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