Digital vs analog volume control?

Jock Wu · « **on:** 31 Jan 2005, 01:34 am »

Which is to be preferred?

Thanks!

Regards,

Joe

TIC · « **Reply #1 on:** 31 Jan 2005, 04:02 am »

Analog.

Digital has the potential to lose resolution because it throws away bits in order to change the volume.

All popular wisdom that I've seen suggest that analog is the way to go.....

Enjoy,

TIC

Marbles · « **Reply #2 on:** 31 Jan 2005, 04:05 am »

Normally I'd say that's true, and certainly generally thats true, but as always there are exceptions.

Wadia (now out of business) had a digital volume control that's better than most analog controls.

And as always, there are varying degrees of quality when it comes to analog volume controls..

TIC · « **Reply #3 on:** 31 Jan 2005, 04:09 am »

Marbles,

You are correct. However, I can tell you, my Quad 99 CDP has an incredible analog volume control. It handily beat my buddy's $4000+ tube pre-amp for transparency. The Resolution Audio Opus 21 that I owned previously also had an excellent analog volume control.

I don't doubt that digital volume control can be very good, but it is certainly more difficult to implement than is a simple, hi-quality analog volume control.

Enjoy,

TIC

Marbles · « **Reply #4 on:** 31 Jan 2005, 04:16 am »

Tom, Jock Wu was very vague in his question.

I agree with your answer for most all instances, except the one I mentioned.

I have an analog volume control because it's the best one I've found among companies still in business.

I thought you gave him good advice....

Rob

TIC · « **Reply #5 on:** 31 Jan 2005, 04:24 am »

Hey Rob,

Do you use CD direct or do you use a pre-amp? Currently I use a single source system with the Quad 99 CDP as source and the Channel Islands VMB-1 as amps, with the Reference 3A MM DeCapos for speakers. It is a really nice, but simple system. The Quad will support other digital sources as it has digital inputs to work as an external DAC. I sometimes play my DVD player through the Quad when listening to music videos. It makes a great, but simple system.

BTW, I never felt comfortable spending what the high end Wadia stuff cost, so I never heard it in my system. I can say that the RA Opus 21 @ $3500 list was a great sounding CD player, but I wasn't comfortable with that many dollars in my CD only unit.

Enjoy,

TIC

Marbles · « **Reply #6 on:** 31 Jan 2005, 04:31 am »

Tom, I use a transformer based pre in my system, the Bent TX102. I use it because I have a CDP(well, a transport and DAC), a phono pre (and of course a Turntable) and I have an integrated 2 channel and HT system so I use the HT passthrough.

If I just had a CDP, I think I would find a great one and not worry about a pre.

PhilNYC · « **Reply #7 on:** 31 Jan 2005, 04:35 am »

Quote from: Marbles

Wadia (now out of business) had a digital volume control that's better than most analog controls..

I think Wadia is still in business...there has been some question about their financial health, but I hadn't heard of their doors finally being shut. At least their phones still work...

As far as their digital volume control works, my understanding is that all Wadia CDP/DACs upsample and use 24-bit words, so that they can "throw away bits" that weren't part of the original sample anyways...so the volume control isn't really any different technically from any other digital volume control in a CDP/DAC that upsamples and uses a 24-bit DAC chip. A lot of the difference comes from how much the Wadia CDPs/DACs upsample (I believe the top of the line DAC oversamples by 32x)...

Marbles · « **Reply #8 on:** 31 Jan 2005, 04:38 am »

I stand corrected on their financial health...must have been a rumour I heard..sorry about that..

CSMR · « **Reply #9 on:** 31 Jan 2005, 04:41 am »

If you have a 16bit DAC and a 16bit source then to do digital volume control you have to throw away bits. But if you have a 24-bit DAC how are you throwing away bits?
I am sure that DACs lose some resolution when functioning at a lower level - whether because of bit-depth or not.
When you put an analog volume control in the chain you must also lose something.
The question is which is normally more detrimental.

PhilNYC · « **Reply #10 on:** 31 Jan 2005, 04:54 am »

Quote from: CSMR

If you have a 16bit DAC and a 16bit source then to do digital volume control you have to throw away bits. But if you have a 24-bit DAC how are you throwing away bits?

A digital volume control "bit shifts" everything down one bit, so you throw away the lowest bit (resulting in a 3db drop in volume). When you upsample something from 16/44.1 to 24/XXX, you are essentially adding 8 bits to your data...but the method for controlling volume is the same regardless of whether you are using a 16-bit DAC or 24-bit DAC. It's just that with a 24-bit DAC, that lowest bit a far smaller portion of the 24-bit word than the lowest bit of a 16-bit word (by something like 1/512). So a company like Wadia can claim that the loss of resolution due to its digital volume control is inconsequential relative to a digital volume control of a 16-bit DAC...

CSMR · « **Reply #11 on:** 31 Jan 2005, 05:13 am »

Yes, I see that with upsampling, the lower bits can have some significance. My point is that the loss of resolution would be inconsequential not only relative to digital volume control on a 16 bit DAC but relative to the (16bit) resolution of the source.

Jock Wu · « **Reply #12 on:** 31 Jan 2005, 12:50 pm »

Thanks for the replies, guys.

My interest stems from looking at pre-amps that have HT bypass...allowing the HT processor to control volume. Then I come across the Talk Hurricane 3.1B http://www.talkelectronics.com/hurricane_3_1.htm which allows one to connect multi-ch in from an HT processor/SACD/DVD-A and then control the volume, using the Hurricane, in the analog domain.

I was also looking at the Bel Canto Pre6 multi-ch pre-amp, but this seems to function like the usual HT bypass.

Cheers!

Joe