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Author Topic: Trying to understand digital volume  (Read 657 times)

zonka

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Trying to understand digital volume
« on: May 06, 2018, 02:42:40 pm »

Can anyone verify if I'm understanding this correctly:  Since the program pads zeros to tracks (all of mine play at 32 bits), then when I'm dropping the internal volume (JRiver program volume) by, let's say, -10db then I'm not losing any useful bits of information - meaning there is no useful degradation of sound quality.

Is this right?

How far would I have to drop the volume (in dbs) to start affecting sound quality?

Thanks for helping me understand:)
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RD James

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Re: Trying to understand digital volume
« Reply #1 on: May 06, 2018, 05:34:33 pm »

As long as you have TPDF dither enabled, there is no loss of quality when reducing the volume in Media Center.
 
The main difference between digital and analog volume control - and this is simplified - is that when you reduce the volume level digitally you are reducing the signal but not the noise. So SNR drops as the volume level drops.
With analog volume control, you are reducing both the signal and the noise floor when you reduce the volume - so SNR remains the same.
 
Now that's not strictly accurate - there are limits on how much you can reduce the volume in the analog domain before it actually does start to affect the SNR, and a high-end DAC will have a noise floor which is essentially as low as you could possibly have with an analog setup anyway due to thermal noise limits.
Digital volume controls are "perfect" while typical analog volume controls may not track linearly, and each channel may not track identically - so you may run into balance issues at low volumes with an analog volume control.
 
If you want to get technical about it, every 6dB is a bit, so if you have a 24-bit DAC and reduce the volume by 48dB it will now be performing like a 16-bit DAC operating at full volume - though a "24-bit" or "32-bit" DAC is probably more like 20-22 bit depending on how high-end it is, so you really have less than 48dB of attenuation.
 
Whether you're going to notice this or not really depends on the amplifier that your DAC is connected to.
If it's got an excessive amount of gain so that a significant volume reduction is required, you may find that there's a noticeable hiss from the amplifier during silent parts.
If the gain is well-matched to your setup, you won't need much volume reduction digitally and the noise floor should be quieter.
 
If you find that you need significant volume reduction digitally, and you are in the lowest gain mode of your amplifier, you may find in-line attenuators useful.
These apply a fixed analog volume reduction, which allows the digital volume level to be set that much higher. (10dB attenuator = +10dB digital volume - or almost 2-bits).
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