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Passive attenuator impedance question

Hi,

I would like to build passive attenuators between my DAC and Amp (to reduce potential degradation in the DAC's digital volume control).

The DAC's output impedance is 100 Ohms and the Amp's input impedance is 100K. Using a 9K/1K resistor network I can achieve the desired 20dB attenuation. If my understanding is right, this attenuator will present itself as a 10K load to the DAC and an output impedance of 1K to the Amp. Both DAC-->Attenuator and Attenuator-->Amp will have a nice 100x impedance ratio. I read in another thread that > 10x is preferable.

Do you think these resistor values (9K/1K) are good, or should I go lower or higher? Obviously I am looking for optimal sonics. I realize the exact values will be system dependent; I'm just looking for some direction.

Thanks,
gmudunuri

Showing 3 responses by zd542

zd542
5,339 posts
 
I don't think you'll benefit in any way by using a passive volume control. I know that when you lower the volume on your dac, you loose some resolution. I've done quite a bit of testing, along with a few other audiophiles that were curious, as well. Using a very detailed system, we couldn't hear any difference whatsoever between low and high settings. I think you're far more likely to lower SQ than raise it. To be fair, we only used Wadia products for our testing. However, I wouldn't expect different results if we tried other brands.
zd542
5,339 posts
 
"07-06-15: Georgelofi

If this is happening Zd542 the dacs volume control is "bit stripping" in the digital domain, this will not happen with a passive volume control in the analog domain."

I know.

"I know that when you lower the volume on your dac, you loose some resolution. I've done quite a bit of testing, along with a few other audiophiles that were curious, as well. Using a very detailed system, we couldn't hear any difference whatsoever between low and high settings. I think you're far more likely to lower SQ than raise it."
zd542
5,339 posts
 
The 121 and 321, I believe are from Wadia's current offerings. I've never used either one, so I really can't comment on how they sound. But I have had many Wadia products over the years, and still have an 861SE and a 302. The owners manuals say to keep the volume above 67 for best sound quality. They also have dip switches (861's are internal, and the 302's are external) that allow you to alter the overall gain so that you can keep the volume setting as high as possible.

Just to make sure we are talking about the same thing, when I did the test, the idea was to see if we could hear a reduction in SQ at volume settings below the recommended 67. Throughout the day of testing, no one, including myself, could hear any difference whatsoever, regardless of low low we set the volume.

Taking the above into consideration, my advice to the OP is to see if you have a problem that needs to be fixed before you start. If you hear a noticeable difference at lower volumes, then it may make sense to try a passive volume control. But if you can't hear a difference, putting the volume control in the signal path, can't do anything positive.
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