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Old 2nd April 2008, 09:38 PM   #1
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Default Very Low Volume Level on DAC

I have built a nos-dac based on a TDA1543 chip. Now I've seen people powering this with different voltages like 5v, 8v or even 9v.
I've powered mine with 5v.
While the overall sound is already pretty good, the volume level is very low.
Could this be the low voltage I used (I believe 5v is recommended) or could this be a resistor thing... Hope you guys can help me out before I start to undo everything.

It's kind of the scheme from RJM

Thanks
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Old 3rd April 2008, 04:32 AM   #2
kevinkr is offline kevinkr  United States
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Sounds like you have insufficient gain after the dac. Are you using passive resistor based I/V or something else? I doubt there is anything wrong with your dac.
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Old 3rd April 2008, 09:00 AM   #3
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Sorry I thought I uploaded an scheme
Here is what I used
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Old 3rd April 2008, 12:59 PM   #4
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Could it perhaps be the fact that in the original scheme the dac voltage is 9v. I however used 5v but maintained the resistor values after the dac as in the scheme?

Sound of the dac is nice. I used the "normal" carbon 0,1w resistors
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Old 3rd April 2008, 02:18 PM   #5
oshifis is offline oshifis  Hungary
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Hey, I read the data sheet and it says the full scale output current is 2.3 mA and the output voltage compliance is +/-25mV. That permits an I/V resistor of maximum 10 ohms. Higher value will lead to distortion. That makes 23 mV peak-to-peak output voltage. You will need a gain stage of about 250 x or an 1:15 transformer after the I/V resistor. In the latter case you can omit the 10 ohms at the primary and put the existing 2.2k at the secondary (it gets transformed to 10 ohms seen by the primary). Then you can omit also the output capacitor and the 100k.

I use a Lundahl LL1678 1+1+1+1:16+16 in my DAC (although with TDA1541A and combined with tube).
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Old 3rd April 2008, 04:54 PM   #6
dddac is offline dddac  Germany
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Quote:
Originally posted by impulz2002
Could it perhaps be the fact that in the original scheme the dac voltage is 9v. I however used 5v but maintained the resistor values after the dac as in the scheme?

Sound of the dac is nice. I used the "normal" carbon 0,1w resistors

you better check what you have really done. Are those values really the ones? Volume should be fine. you will have 1.6V RMS at 0dB. Easy to check with a 100Hz testtone and a multimeter

but ONLY when you use 8 - 9 Volt. If you really have 5V and 2k2, it will CLIP your tweeters out. That is why I doubt heavily...

forget the datasheet compliancy thing. The TDA1543 sounds great when implemented right (see my website for more background)

measure a few things and let us hear !
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Old 3rd April 2008, 05:14 PM   #7
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Quote:
Originally posted by dddac



you better check what you have really done. Are those values really the ones? Volume should be fine. you will have 1.6V RMS at 0dB. Easy to check with a 100Hz testtone and a multimeter

but ONLY when you use 8 - 9 Volt. If you really have 5V and 2k2, it will CLIP your tweeters out. That is why I doubt heavily...

forget the datasheet compliancy thing. The TDA1543 sounds great when implemented right (see my website for more background)

measure a few things and let us hear !



I think I'm still sleeping. Thanks for the advice. Looked at it and I made a mistake. I used 1k as output resistors instead of 2k2.
Any advice regarding values for resistors to use and can I keep the 5v or is it better to make it 8v for the dac.
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Old 3rd April 2008, 05:21 PM   #8
dddac is offline dddac  Germany
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Quote:
Originally posted by impulz2002





I think I'm still sleeping. Thanks for the advice. Looked at it and I made a mistake. I used 1k as output resistors instead of 2k2.
Any advice regarding values for resistors to use and can I keep the 5v or is it better to make it 8v for the dac.

That makes much more sense now .... this implies the volume is 7dB lower which is clearly audible versus "normal" CD players....

try 8,5 Volt and 2k2 ? you will like it for sure !
Rref 1k5....

doede
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Old 3rd April 2008, 05:41 PM   #9
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Quote:
Originally posted by dddac



That makes much more sense now .... this implies the volume is 7dB lower which is clearly audible versus "normal" CD players....

try 8,5 Volt and 2k2 ? you will like it for sure !
Rref 1k5....

doede
Thanks.

Any advice on resistor value if I hang on to 5v. It doesn't need to be that loud, but now it's just too low. 820 maybe?
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