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Old 3rd October 2011, 06:33 AM   #71
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Maybe the ESS DAC sounds light in the voltage mode into a transformer because it really does not like the low impedance of it. How about adding National zero feedback buffers on each output and then going through a tranny (Audio Consulting trick). You could then use a low impedance tranny for less copper signal loss. Output impedance would be seriously low. Even if you used it as a 1 to 2 to get 4VRMS the output impedance would still be relatively low (assuming 40 ohm windings). Most DACs cannot drive a tranformer directly without some dynamics loss. This is what I have heard. The transparency is great, but once you add the buffer.....the slam and body is back. Of course, the execution of the power supply and bypassing for the buffers has to be top notch.
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Old 3rd October 2011, 10:52 AM   #72
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Quote:
Originally Posted by Ric Schultz View Post
Maybe the ESS DAC sounds light in the voltage mode into a transformer because it really does not like the low impedance of it.
Absolutely, the "it" being the transformer.

Quote:
Originally Posted by Ric Schultz View Post
How about adding National zero feedback buffers on each output and then going through a tranny (Audio Consulting trick). You could then use a low impedance tranny for less copper signal loss. Output impedance would be seriously low.
National LMH6321 comes to mind - and what you say is quite correct, but it is not the solution that I seek which is to eliminate active circuitry if possible.

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Originally Posted by Ric Schultz View Post
Most DACs cannot drive a tranformer directly without some dynamics loss. This is what I have heard. The transparency is great, but once you add the buffer.....the slam and body is back. Of course, the execution of the power supply and bypassing for the buffers has to be top notch.
Again I agree that low Z into the Primary is an advantage for the sonic reasons you describe. So we are on the same page. Most voltage DACs (the ones I like) have reasonably low output Z and I would recommend a transformer there. But alas the Sabre DAC is not an ideal voltage DAC.

Try my suggestion. I think you will be very pleased with the result for very little complexity. In my system the '95 with clocks on both MHz and 54MHz (80MHz) does not sound light weight tonally. The transparency is extraordinary.

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Of course, the execution of the power supply and bypassing for the buffers has to be top notch.
Exactly. You and I can play with active buffers, and do, but many more DIY'ers can do this little two resistor trick, right? Especially the fact that many of the Buffalo gang do use txs.

Cheers, Joe R.
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Last edited by Joe Rasmussen; 3rd October 2011 at 10:55 AM.
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Old 3rd October 2011, 12:27 PM   #73
Coris is offline Coris  Norway
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[QUOTE=Joe Rasmussen;2732608]I have now fitted two clocks on the BDP-95.

I have the 25MHz on the main/digital board and now replaced the 54MHz on the daughter board with an 80MHz clock.



Did you used something special oscillator as replacement for that 54Mhz one, or an standard one? What about to use an f. ex. 125Mhz clock in the place of that 80Mhz? Just try it...
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Old 3rd October 2011, 01:41 PM   #74
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Did you used something special oscillator as replacement for that 54Mhz one, or an standard one? What about to use an f. ex. 125Mhz clock in the place of that 80Mhz? Just try it...
A couple of things...

I used the Terra Firma Power Supply and it has a limited max current it can provide. So adding an extra oscillator presented a problem.

Most oscillators require increased current as the frequency increases. Just look up a few datasheets and you'll find that out. But I was able to source an 80MHz oscillator and measured 17mA - so that was just low enough to get by.

BTW, the chief purpose of the power supply is to supply low noise down to even sub-1Hertz - and this is even more important than the quality of the oscillator itself (but not recommending rubbish here). We've found that doing both clocks is necessary.

Cheers, Joe R.
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Old 3rd October 2011, 03:36 PM   #75
Coris is offline Coris  Norway
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Quote:
Originally Posted by Joe Rasmussen View Post
A couple of things...

I used the Terra Firma Power Supply and it has a limited max current it can provide. So adding an extra oscillator presented a problem.

Most oscillators require increased current as the frequency increases. Just look up a few datasheets and you'll find that out. But I was able to source an 80MHz oscillator and measured 17mA - so that was just low enough to get by.

BTW, the chief purpose of the power supply is to supply low noise down to even sub-1Hertz - and this is even more important than the quality of the oscillator itself (but not recommending rubbish here). We've found that doing both clocks is necessary.

Cheers, Joe R.

You can feed those oscillators from dedicated power supplies... I didn`t get exactly what you refer about problems because extra oscillators. It is also the best to build an dedicated power supply for that oscillator you want to use, in that place it have to be used... There are many low noise chips/regulators which can very well do this job.
Else, I just heard the sound difference when used in a DAC an 100ppm oscillator, and when used an 0,3ppm oscillator (with the same frequency and the power supply). I can tell you that is huge...
I have some more questions (with your permission): do you still use that original Oppo`s (analogue/serial) power supply in BDP95?. Did you trust it as a low noise one? Did you used the same original place Oppo chosen for their 54Mhz clock on the audio board (in the middle of the board)?
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Old 3rd October 2011, 11:26 PM   #76
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Quote:
Originally Posted by Coris View Post
I have some more questions (with your permission): do you still use that original Oppo`s (analogue/serial) power supply in BDP95?. Did you trust it as a low noise one? Did you used the same original place Oppo chosen for their 54Mhz clock on the audio board (in the middle of the board)?
The new clock supply has a totally independent power supply (even has its own power transformer wired straight to the IEC AC Input) that in this particular instance takes 30 Minutes to come on. No, nothing of the player's internals are used. And both 25MHz and 80MHz oscillators are our choice and wired in.

Cheers, Joe R.

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Last edited by Joe Rasmussen; 3rd October 2011 at 11:30 PM.
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Old 4th October 2011, 06:42 AM   #77
Coris is offline Coris  Norway
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[QUOTE=Joe Rasmussen;2733650]The new clock supply has a totally independent power supply (even has its own power transformer wired straight to the IEC AC Input) that in this particular instance takes 30 Minutes to come on. No, nothing of the player's internals are used. And both 25MHz and 80MHz oscillators are our choice and wired in.

Cheers, Joe R.


Fine! Thanks for the answers.
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Old 8th October 2011, 05:59 PM   #78
Coris is offline Coris  Norway
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IT IS RIGHT!
Changing the main clock 25Mhz of the main processor, leads to a big general improvement. The biggest improvement is in the image/video quality. A big increase in gradients, tonal details, colour details and details in general in both pictures and film/video. A big surprise!
Not at least a big improvement in sound. The same, more details and wider sound stage. More volume in the sound. Is hard to define... The clearness of every single sound is astonish.
I`ve used an so called standard oscillator, but a high precision one. An 0,5ppm from Digikey. Very low noise single chip 3,3v regulator dedicated to the oscillator and feed it from 8v original regulator as seen in the pictures here by.
I still have an 125Mhz clock on the audio board (ES9018)... It sounds just superb!

What is possible to happen if changing the rest of these very low quality Oppo`s oscillators in this "high end" BDP95...?
Why should need so many and big modifications this Oppo player for have that really high quality it is sold as? Do you have the answer Oppo company?
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Last edited by Coris; 8th October 2011 at 06:05 PM.
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Old 9th October 2011, 05:20 AM   #79
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Quote:
Originally Posted by Ric Schultz View Post
<SNIP>
Many people do this already. Look at the last pics of Coris's DAC. A ton of large value ceramics directly on top of the DAC chip.
<SNIP>
Question for Coris actually... what capacitors, make, model, package, and value, did you use for bypassing on top of the DAC back in post 49?

THANKS!

Greg in Mississippi
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Old 9th October 2011, 08:16 AM   #80
Coris is offline Coris  Norway
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Quote:
Originally Posted by Greg Stewart View Post
Question for Coris actually... what capacitors, make, model, package, and value, did you use for bypassing on top of the DAC back in post 49?

THANKS!

Greg in Mississippi
Hi
I`ve used in that place quite normal ceramic capacitors 100/6v. Is not a very special capacitor model/package in that case. I will not recommend to use an only one (big) capacitor for decoupling. A pack made of many small caps as shown in the picture is the best way...
Else, I`m not so satisfied about that arrangement right on the top of the chip, because the chip get warm a little bit, and that type of capacitors are not so happy to get warm in that way... But is quite difficult to find a better position in that design.... It think now that is better to mount the capacitor pack 1-2mm above the chip, not right on the chip.
I have now there 2x1000. The picture is a little bit old now... There is improvement in this way, but is not spectacular, if the another mods are not done yet... If we talk about this particular case (BDP95). The best over all result is when decoupling in this way too the I/V stage and specially the final stage... One can see a also the decoupling on I/V stage in that picture. For I/V stage I`ve used tantalum caps 220/20v (the orange ones) together with ceramics (100/16v). The tantalum caps (very low ESR) are a better choice for the I/V & final stage. Local regulators (with appropriate capacitors) are a must of course in this case, for best result.
One have to take in to consideration that large decoupling capacities mean some problems at power start up and shut down. There is a large start up current for the regulator (if a local regulator is use), and a large energy which left stored in that capacitors after power down. An adequate local voltage regulator with current limit protection will solve this very well.
This decoupling do not represent a issue for the main power supply.

If you want to go this "decoupling" way, you may want to do the another important mods before this one. This should be my choice, but you can of course chose another way...
Nice to hear from you about the finally results...

Last edited by Coris; 9th October 2011 at 08:26 AM.
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