What is the advantage of the volume control design in Zodiac DACs?

This is the next of the series of video-posts in which Igor Levin talks about Antelope Audio technologies.
It is time to discuss Antelope’s D/A converters (DACs) and in particular the design of the volume control.
In this post Igor talks about the specifics of the volume control within Zodiac DACs and explains why Antelope implements it in the analog part and not in the digital. The result is a much more accurate stereo placement of the audio especially in the lower listening volumes.

For more details about the benefits of the volume control design in Zodiac DACs watch the short video and please, feel free to share your opinion.

The important thing to know is that, in all of the Zodiac families the volume adjustment is always done in the analog way. Because cheaper DACs and not only cheaper, many of the competitors’ DACs, when you adjust the volume, you’re not doing it with an analog potentiometer, you are changing the signal digitally. It’s actually changing the digital numbers that are being fed to the D/A converter. It’s doing it with the digital mathematics and that is not thought to be as good. It’s better to convert it at the highest level possible and then reduce the level using analog potentiometers because when you take the numbers and reduced them numerically by multiplying them by a smaller number, you’re losing the resolution, you’re losing some of the Bits. So that’s why, in professional products the adjustment of the volume should be done in the analog way, not done digitally.
So, in Zodiac Classic, in Zodiac Plus & in Zodiac Gold, these are analog adjustments. In Zodiac Classic or in Zodiac Plus, that’s a potentiometer that you’re turning. In Zodiac Gold, we’ve moved up another notch. Potentiometers, they’re sort of… again it’s an analog device, which has to be calibrated, providing different resistance for a different angle of rotation. But it’s really hard to get the left and the right channel tracking perfectly because it’s a mechanical alignment issue. So, as a result, as you lower the volume, sometimes the stereo-tracking gets to be affected and so sometimes at the lower listening volumes, like minus forty dB, the tracking of left and the right channel… – they can misalign as much as two- three dB’s. That’s significant.
When you use the pot, it’s best to keep the levels towards the top range, say between zero to twenty dB’s and not to go down too much. So, when we were doing Gold, to avoid that issue that has to do with the mechanical tracking of the pots, we went to a relay based volume adjustment. In this case, precision resistors are used to establish the level and the relays, which are electronically operated switches, basically step between each level in steps, in one decibel steps, but each step… The quality and the precision of each step is determined by a 0.1 percent accurate resistor and so as a result you’re talking about… a dB tracking which is 0.05dB less than one tenth of a dB mis-tracking, whereas, in a conventional pot you could have several dB mis-trackings. So we’re talking about improvement that’s a hundred times or more in terms of accuracy.
So, that’s why in Gold, we use relays. That’s also very unique. There’s very few worldwide DAC products that use relay stepping and there’s virtually none in the same format. Now, we have a unique small format that makes it very convenient to hold it in a desktop, to move it around, you know, to go along with your laptop. So, to have, in such small format, relay-based stepping is very very cool.