| zuus |
I have a Derek Shek NOS DAC and got curious so I thought I would remove the ref resistor (a variable one on this DAC). The data sheet says it is optional, but when I remove it, despite getting music at much reduced volume I also get a kind of digital noise. The resistor is set to 1.47kohm and gives 4.35v at the output pins, perhaps a little high??
Does anybody have any thoughts on this, do I have a faulty DAC?.
Regards,
Mark |
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| maxlorenz |
Hi Mark:
I'm not a technical guy but I'll try to help :angel: | quote: | | The data sheet says it is optional |
Which data sheet? Philips data sheet or your DAC's data sheet?
AFAIK, Rref is mandatory for the DAC to work. It must fix Vref between 2 and 2.2VDC for proper functioning and lack of (excess :D ) HF noise. Maybe it says "variable R is optional IF you swap it for a fixed one!". For fixed Rref I believe it got to be between 0.6 and 0.7/Rload.
If you let it without Rref you will get oscilation and much HF noise. (Did I say it well, guys? :( )
Use hi quality R for Rref and Rload. I use Riken-Ohm (it is said that they sound warm due to higher noise but I don't care!)
| quote: | | The resistor is set to 1.47kohm and gives 4.35v at the output pins, |
Do you mean Rload (signal to ground) is 1K47? Yes 4.35 is a bit high. Something between 3.6-3.85VDC looks better to my non-expert eyes (and even that could throw UHF noise to the next stage) .
There is plenty of info here. Also search for Philips TDA1543 data sheet.
Good luck.
M
PS: you have your output DC blocking cap, don't you? |
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| zuus |
| quote: | Originally posted by maxlorenz
Hi Mark:
I'm not a technical guy but I'll try to help :angel:
Which data sheet? Philips data sheet or your DAC's data sheet?
AFAIK, Rref is mandatory for the DAC to work. It must fix Vref between 2 and 2.2VDC for proper functioning and lack of (excess :D ) HF noise. Maybe it says "variable R is optional IF you swap it for a fixed one!". For fixed Rref I believe it got to be between 0.6 and 0.7/Rload.
If you let it without Rref you will get oscilation and much HF noise. (Did I say it well, guys? :( )
Use hi quality R for Rref and Rload. I use Riken-Ohm (it is said that they sound warm due to higher noise but I don't care!)
Do you mean Rload (signal to ground) is 1K47? Yes 4.35 is a bit high. Something between 3.6-3.85VDC looks better to my non-expert eyes (and even that could throw UHF noise to the next stage) .
There is plenty of info here. Also search for Philips TDA1543 data sheet.
Good luck.
M
PS: you have your output DC blocking cap, don't you? |
The TDA1543 data sheet (the DAC doesn't have one), says Rref is optional (if I read correct). I gather from what you say that if I replace the adjustable with a fixed one, that would be an improvement. Rload is (for left and right) 2.7Kohm (to give standard output level I guess). So the 4.35 on these is too high then?
Also yes I do have dc blocking caps (3.3uF RIFA (whoever they are)), too low??
Kind Regards,
Mark |
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