Digital Volume Controls

StingRay

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Yes that's right. The 'power' level coming out to the speakers will be exactly the same.

There is a widespread misunderstanding between gain and power. Power is only added at the output (last) stage of the amplifier in order to drive the speakers properly.
The rest of the circuit will be providing voltage gain tempered with the attenuation of whatever is used to control the volume, be it a digital chip or a potentiometer.
I see what you are saying but what if the input is low, there may not be enough volume on the amp, say I reduce the DAC to 5%, the amp. may run out of volume.
 

MartinC

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I'm only using a digital volume control or so I thought. Not sure what difference it makes. I have active speakers.

If you have two options for volume adjustment in the digital domain then I guess it depends which has the better implementation then. If one was 24 bit and the other 32 bit I'd use the latter for example. Or go with whichever is most convenient if you can't tell and difference in quality terms :).
 

StingRay

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If you have two options for volume adjustment in the digital domain then I guess it depends which has the better implementation then. If one was 24 bit and the other 32 bit I'd use the latter for example. Or go with whichever is most convenient if you can't tell and difference in quality terms :).
Its usually recommended that the DAC is 100% volume and then the volume is controlled on the amp. Controlling the volume on my DAC, is not very easy, as it to have large steps, whilst on my actives remote I can adjust it finely. My other DAC does not even have a remote. Putting my actives on full volume, would be quite risky, as it's extremely loud, as I found out by mistake once and it was not even full volume.
 

MartinC

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Its usually recommended that the DAC is 100% volume and then the volume is controlled on the amp.

I'd suggest you're referring to old advice, considering poorer volume adjustment in the digital domain and assuming analogue adjustment further along the signal path. The modern situation is more nuanced as per the discussion above.
 

andrew s

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Even with an ideal digital volume control the best S/N ratio is with the DAC at 100% and the analogue attenuation placed as late as possible in the chain. This is especially true at low levels as the analogue control reduces the signal and noise in step (excepting for a buffer stage) while this is not the case for the digital attenuator where all the analogue upstream noise persists as the volume is decreased.

This is why Benchmark introduced the DAC3 B (without a volume control) and the analogue LA4 preamp to match the low noise of the AHB2 power amp. It also important to have matching i input and output levels along the chain for best performance.

Regards Andrew
 

StingRay

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I'd suggest you're referring to old advice, considering poorer volume adjustment in the digital domain and assuming analogue adjustment further along the signal path. The modern situation is more nuanced as per the discussion above.
I will continue to use my DACs in pure DAC mode. Control the volume on my active speakers.

I have read the preamps in budget DACs are not that good.
 
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Alan

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Every system is different, every DAC is different as well.

My DAC has no 'pre amp', just a sophisticated digital control; an attenuator. It would never need to amplify: it outputs a frankly ridiculous 4V plus over RCA and in excess of 6V on XLR. Most amplifiers need how much for maximum output again?

So in the context of a system like mine, with minimal to negligible losses from the DAC even close to maximum attenuation, digital volume control is an elegant solution. My system still sounds better with really good analogue pre-amplifier in the circuit, it buffers the source beautifully. Which is why I keep the pre amplifier volume at a 'halfway' position (as I said, I wouldn't want to run the DAC at 100% even at this level).
 

MartinC

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I have read the preamps in budget DACs are not that good.

For DACs that adjust volume in the digital domain, the output stage will usually be identical whether attenuation is applied or not.

From a quick Google it looks like your DAC probably adjusts volume in the analogue domain, which is very different.
 

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Digital volume control isn't lossless though. Here's a good demonstration with measurement what happens when you lower volume level on Linn Akurate DSM Katalyst:


About halfway down the first post to see the measurements and loss of resolution while using digital volume control. The post is quite readable with google translate.

So an absolute purist way to adjust volume would probably be as transparent as possible analog volume control, possibly passive one like Khozmo or Goldpoint. Benchmark LA4/HPA4 should be perfectly transparent also.
 

MartinC

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The thing to remember when considering limitations of digital volume adjustment is that analogue volume adjustment isn't perfect either.

For myself I use a digital volume control as there is no viable alternative with my current setup.
 
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StingRay

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For DACs that adjust volume in the digital domain, the output stage will usually be identical whether attenuation is applied or not.

From a quick Google it looks like your DAC probably adjusts volume in the analogue domain, which is very different.
Not according to some users, it's in the digital domain. You are referring to my Soncoz DAC?