Passive attenuator impedance question

"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."

Regarding "bit stripping," I would not extrapolate experience with Wadia models to models from other manufacturers, and perhaps even between different Wadia models.

The manual for the Wadia 121 states as follows:

Does the Wadia Volume Control compromise resolution?

The Wadia 121 Decoding Computer uses the latest generation of Wadia’s proprietary digital volume control. The volume level can be varied in the digital domain by means of mathematical manipulation of the signal, eliminating the distortion and noise that are inevitable with even the best analog volume controls. While conventional thinking indicates that reducing the volume digitally can sacrifice low level resolution, Wadia has created an innovative solution. Wadia’s patented digital filtering algorithm produces a 32-bit output. This high-resolution signal is then used in the computations that in turn reduce the volume level. This new signal is fed directly to the DAC chips. Through this innovative method, the Wadia 121 Decoding Computer maintains high resolution even at the lowest volume control settings.

While the manual for the 321 has no such statement but says:

A Volume Setting of 88% on the Wadia 321 will provide optimum performance when it is connected to a Preamplifier (Integrated Amplifier or Receiver).

Best regards,
-- Al

Mr G- Something that may be of interest to you: (http://www.partsconnexion.com/controls_attenuator_khozmo_series.html)

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.

Just a few thoughts as I'm a passive guy ... your impedance's are fine as Al has confirmed but we don't know anything about the V/out of the source and your V/in of the amp



Because you've eliminated the ... Pre which usually takes the responsibility of driving the IC to the amp ... your source is now the driving everything



I think the IC between the Passive's output and the amp's input is much more critical than the Digital vs Analog volume control debate



The IC from your passive attenuator should be very low in capacitance and as short as possible to keep from rolling off the highs ... Al can expound on this and the V/out V/in through the passive



On the digital vs analog volume control debate ... all volume control/attenuators sound best at full volume as they have little or no resistance in the circuit to degrade the sound when set to FULL



If a digital volume controls throws away bits and compromises the sound ... then I say a analogue volume controls have to many resistors or resistance in the circuit at low volume to attenuate the volume and compromises the sound equally ... 6 of one a half dozen of another



I cheat ... after my source I use a Burson class A no neg feedback buffer feeding the volume controls in my Phase Linear D500 to do the driving



The P/Linear's volume controls are a compromise but I also have a modded P/L D500 which I've bypassed the V/Controls on and will be using a Slagle auto former set up that I'm just finishing up



The Slagle A/F doesn't suffer the bit drop out of the digital V/C or the resistance issues of a typical resistor based passive V/control and it does a better job of shifting less as you turn the V/C up or down



Something not mentioned or considered is the shift in impedance as the V/C is turned up and down and again Al can easily explain this better than I