Pre 1 preamp vs Topping Pre90

Hi Alan,

I’m of course no expert on these matters, but my reading suggests that using the digital volume control on my intended Gustard X26 III DAC, driving a P282 directly, would reduce bit depth by truncating digital data, especially at lower volumes, thus degrading resolution, dynamic range, and low-level detail. Is this not the case?

Cheers,

Ash

Ash wrote:
Hi Alan,

I’m of course no expert on these matters, but my reading suggests that using the digital volume control on my intended Gustard X26 III DAC, driving a P282 directly, would reduce bit depth by truncating digital data, especially at lower volumes, thus degrading resolution, dynamic range, and low-level detail. Is this not the case?

Cheers,

Ash

Hi @Ash

There is a bit of a misunderstanding generally about how digital volume controls work. I cant comment specifically on the Gustard as I dont know how its implemented, but here is a general comment.

The calculations for a digital volume control should be performed at higher bit depth than the actual recording you are playing, so 32 or 64 bit. I use Roon software and it uses 64 bits.

Doing this means that no resolution is lost. For info 16 bit has 65535 signal levels, 24 bit has 16,777,215 levels, 32 bit has 2,147,483,647 levels and 64 bit has 9,223,372,036,854,775,807 levels.

Also it should be noted that real world recordings simply dont acheive 24 bit resolution (SNR). 18 to 19 bit is about the best you will find.

Also that real world noise levels in the best electronics (dacs, surrounding amp circuitry etc) only reaches about 22/23 bit.

So "resolution" is a non issue with digital volume.

A real theoretical disadvantage of digital volume is as follows.

All electronics have a level of noise. A DAC will produce a certain level. When using a "perfect" analogue volume pot, when you turn it down both the music signal level *and* the inherent background noise of the source will turn down also. As such in theory it will maintain the signal to noise ratio.

Using a digital volume, when you turn it down the music signal level decreases but the inherent source background noise remains the same. As such signal to noise ratio decreases.

So that's a real theoretical disadvantage. Now let's step back into the real world.

Source electronics noise levels are now so low that this potential disadvantage is irrelevant. DACs are around 130dB SNR. The noise is completely inaudible and then some.

Analogue volume controls aren't perfect. They will *always* be noisier. They will have issues such as balance tracking (although much better with stepped ladder).

Power amplifiers will be the noisiest part of any signal chain as they have a lot of gain to raise the source signal to levels able to drive speakers. The power amp will be the limiting factor in most systems.

So, all the concerns about digital volume controls are moot in a real world system. If properly implemented they will always perform better than an analogue control.

The only reason to have a pre amp is if you have multiple sources (dac, streamer, turntable etc) and need to switch between them. Otherwise a DAC/streamer run directly into a power amp will perform better.

Just an aside, when recording and mixing music these days in the studio, A DAW (digital audio workstation) is usually used. The mixing volume level changes for each instrument is done with 64 bit digital volume control.

In conclusion, dont be concerned in any way about digital volume control. I would always use it in preference to analogue.

Hope that helps

Hi @Ash

I've looked at the Gustard, its a good performer and I wouldn't hesitate to use its own own volume control.

Alan March wrote:
…

Power amplifiers will be the noisiest part of any signal chain as they have a lot of gain to raise the source signal to levels able to drive speakers. The power amp will be the limiting factor in most systems.

If we are talking about distortion, then ^this^ is 100% not true.
If you are talking solely about noise, then maybe you;re correct… but unless one is putting their melon next to the tweeter, the noise is largely inaudible.

For distortion then maybe a SET amp with your speakers playing low, has the amps as the highest distortion in the chain.
But in general the speakers dominate distortion by orders of magnitude.
And certainly with any amp that is decent the speakers with distortion at say -30dB totally dominate.
If they are being played low and with distortion around -60, then still most decent amps have THD+N below -70dB.

Alan March wrote:
So, all the concerns about digital volume controls are moot in a real world system. If properly implemented they will always perform better than an analogue control.

Or at least well enough.
But a good preamp is also just dandy.

Alan March wrote:
The only reason to have a pre amp is if you have multiple sources (dac, streamer, turntable etc) and need to switch between them. Otherwise a DAC/streamer run directly into a power amp will perform better.

^I abide.^

Alan March wrote:
Just an aside, when recording and mixing music these days in the studio, A DAW (digital audio workstation) is usually used. The mixing volume level changes for each instrument is done with 64 bit digital volume control.

In conclusion, dont be concerned in any way about digital volume control. I would always use it in preference to analogue.

Hope that helps

^100%^

Holmz wrote:
If we are talking about distortion, then ^this^ is 100% not true.
If you are talking solely about noise, then maybe you;re correct… but unless one is putting their melon next to the tweeter, the noise is largely inaudible.

Erm...well...yes, I 100% agree. Speakers are horrible in terms of disrortion compared to electronics. However, we were talking specifically about noise. In this context, the speaker distortion issue applies just the same to analogue and digital volume controls.

Also it should be noted that amplifier noise becomes a very real audible issue when using high sensitivity speakers < 100dB such as horns.

Holmz wrote:
Or at least well enough.
But a good preamp is also just dandy.

No, correctly implemented digital volume will beat a simple analogue control every time. A hybrid control can be used to optimise SNR (see RME DACs), but that's not the case with typical pre amps.

Whilst the best pre amps are audibly transparant, there are a lot of pretty mediocre ones out there. Essentially, even the best pre amp can only add to noise, distortion and colouration. If you only have one source, i.e a DAC/streamer, then dont use a pre amp.

Yep - I just wasn’t sure if the OP was talking about noise or distortion or both.

Luckily I have an RME or two, and a relatively good preamp… as I need a preamp to switch between a TT and other gear.

Alan March wrote:
...
No, correctly implemented digital volume will beat a simple analogue control every time. A hybrid control can be used to optimise SNR (see RME DACs), but that's not the case with typical pre amps.
…

Not all of them may be correctly implemented though… how does one know?

Holmz wrote:

Not all of them may be correctly implemented though… how does one know?

Good question. Simple answer is that you dont know for sure unless you have test data. However, this is the same for any component, including analogue volume controls.

I have to say that I have never come across a defective digital volume control. I have seen some pretty mediocre pre amps.

What happened to the Pre 1 preamp? It's still not listed on your website, unless I'm mistaken.

Alan March wrote:
Hi @Ash

I've looked at the Gustard, its a good performer and I wouldn't hesitate to use its own own volume control.

Thanks for all of that, Alan. Given that my current plan is to play ALAC/DSD from my MacBook Pro, using Audirvana, USB C-B, a Gustard U18 DDC, HDMI into the Gustard X26 III DAC, and a CD transport (probably Audiolab 9000 CDT) through coaxial cable into the X26, then XLR into your P282, you’ve persuaded me not to buy your Pre1, at least in the first instance! Clayton Shaw has finally finished my Caladans, 6 months late, so hopefully I’ll have them in a month or so. As soon as I know when they’re arriving, I’ll get all the new electronics, so it can all burn/break in together!
Thanks again,
Ash