Hi, I was looking at the Wimm vibe link amplifier for using with the optical out on a audio source such as tv or internet radio streamer and was wondering if using the remote on the source to reduce volume will reduce the bit depth being delivered to the Wiim and will this be noticeable in practical terms.
https://www.wiimhome.com/wiimvibelink/overview
I could of course use the analog volume dial on the Wiim amp, but that would mean no remote control which may be annoying at times.
Does digital volume reduction affect bit depth
Does digital volume reduction affect bit depth
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- BrendanGartner
New here - Posts: 6 Joined: Thu Jan 16, 2025 1:17 am
Re: Does digital volume reduction affect bit depth
Personal bug bear.. bits don't have a depth!
In PCM digital audio coding, bits form words. More bits means longer words... so the correct term is Word Length.
So, does digital volume reduction affect word length?
The answer is both yes, and no.
No because the wordlength remains the same. If 24 bits go into the digital volume control, 24 bits will come out, too.
But yes if you're interested in the number of active bits representing the audio amplitude.
In a digital volume control, each sample word is multiplied by a number to adjust the audio data amplitude. X2 makes it 6dB louder. X0.5 makes it 6dB quieter... and so on.
It is critically important to note that any multiplication process must be followed by redithering to avoid quantising distortion.
If the volume is turned down, by multiplying by a small number, fewer bits remain active, so you could argue that the word length is effectively being reduced.... which I think is the crux of your question.
So the D-A after a gain reduction process might be converting 24 active bits at full volume, but only 16 or 12 active bits at a reduced volume.
To understand the implications of that we need to know what the difference is between a 24 bit signal and a 16 bit signal?
An audiophool would say (incorrectly) 'resolution', but an engineer would say signal-to-noise ratio (SNR).
In a 24 bit signal the SNR is about 141dB, whereas it's around 93dB in a 16 bit signal, and about 69dB in a 12 bit signal.
So, from that you can see that if you turn down a digital volume control the SNR reduces and, in effect, the signal gets noisier.
Is that a problem?
No!
EXACTLY the same thing happens when using an analogue volume control, and for exactly the same reason.
Both analogue and digital systems have a fixed noise floor. In analogue systems its due mostly to the Johnson noise of the electronics. In digital systems its due to dithering.
If you reduce the amplitude of the audio in either domain, the range between peak audio level and noise floor reduces, so the SNR is reduced.
And that's it. The laws of physics (and communications theory) apply in both digital and analogue domains
Both analogue and digital volume controls do exactly the same thing and have exactly the same side-effects. Audio resolution is not lost, but a quieter signal is closer to the noise floor so will sound a little noisier, in both analogue and digital systems.
So feel free to use the digital remote control on your Wiim. It will work perfectly, just as an analogue volume control would — but better, actually, because the stereo tracking will be significantly better, especially at extreme settings, and the dither noisefloor of a 24 bit D-A converter is potentially lower than the noisefloor of an analogue preamp!
In PCM digital audio coding, bits form words. More bits means longer words... so the correct term is Word Length.
So, does digital volume reduction affect word length?
The answer is both yes, and no.
No because the wordlength remains the same. If 24 bits go into the digital volume control, 24 bits will come out, too.
But yes if you're interested in the number of active bits representing the audio amplitude.
In a digital volume control, each sample word is multiplied by a number to adjust the audio data amplitude. X2 makes it 6dB louder. X0.5 makes it 6dB quieter... and so on.
It is critically important to note that any multiplication process must be followed by redithering to avoid quantising distortion.
If the volume is turned down, by multiplying by a small number, fewer bits remain active, so you could argue that the word length is effectively being reduced.... which I think is the crux of your question.
So the D-A after a gain reduction process might be converting 24 active bits at full volume, but only 16 or 12 active bits at a reduced volume.
To understand the implications of that we need to know what the difference is between a 24 bit signal and a 16 bit signal?
An audiophool would say (incorrectly) 'resolution', but an engineer would say signal-to-noise ratio (SNR).
In a 24 bit signal the SNR is about 141dB, whereas it's around 93dB in a 16 bit signal, and about 69dB in a 12 bit signal.
So, from that you can see that if you turn down a digital volume control the SNR reduces and, in effect, the signal gets noisier.
Is that a problem?
No!
EXACTLY the same thing happens when using an analogue volume control, and for exactly the same reason.
Both analogue and digital systems have a fixed noise floor. In analogue systems its due mostly to the Johnson noise of the electronics. In digital systems its due to dithering.
If you reduce the amplitude of the audio in either domain, the range between peak audio level and noise floor reduces, so the SNR is reduced.
And that's it. The laws of physics (and communications theory) apply in both digital and analogue domains
Both analogue and digital volume controls do exactly the same thing and have exactly the same side-effects. Audio resolution is not lost, but a quieter signal is closer to the noise floor so will sound a little noisier, in both analogue and digital systems.
So feel free to use the digital remote control on your Wiim. It will work perfectly, just as an analogue volume control would — but better, actually, because the stereo tracking will be significantly better, especially at extreme settings, and the dither noisefloor of a 24 bit D-A converter is potentially lower than the noisefloor of an analogue preamp!
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- Hugh Robjohns
Moderator -
Posts: 43700 Joined: Fri Jul 25, 2003 12:00 am
Location: Worcestershire, UK
Contact:
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
Re: Does digital volume reduction affect bit depth
Thanks Hugh, that’s good to know. I think I’ll go for the Tangent Ampster instead of the Wiim, it might not be the same quality but works out about half the price and seems to get good reviews.
Many thanks and best regards.
Many thanks and best regards.
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- BrendanGartner
New here - Posts: 6 Joined: Thu Jan 16, 2025 1:17 am