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The final truth about DSP Volume Control in Roon

DrCWO

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In the net I found a lot of discussions regarding the quality of Roon DSP volume control.

The discussions revolve around whether it is better to use the device volume, the DAC volume, or
an analogue volume control. One of these threads for example here:
https://community.roonlabs.com/t/better-volumecontrol/126279/13

My concern was to find out the truth about DSP volume control in Roon by measurements just
to know and to let you know.

Please see all the details in the attached whitepaper.
 

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  • Whitepaper Roon DSP Volume Measurements.pdf
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PaulD

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For those who are time-poor, from the paper:

---
Conclusion

The DSP volume control inside the Roon Bridge is as perfect as can be.

The noise floor remains at -178dB, regardless of which attenuation is set for the DSP volume. This means that even at volumes down to -50dB the dynamic at the output is higher as the signal to noise ratio of the best DACs and power amplifiers. No other issues like intermodulation artefacts between the two frequencies or other distortions have been found. The dither is very well done with a completely flat response.

My conclusion is that there is nothing at all to worry about DSP volume in the Roon Bridge. No analogue volume control in the word can deliver these results. The thermal noise of a potentiometer or an analogue ladder attenuator will be much higher than the -178dB the DSP volume control of Roon delivers.

My recommendation: Use DSP Volume whenever possible.[/QUOTE
---

Generally matches the conclusions of other papers I have seen about digital volume controls. :D
 
Last edited:

solderdude

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In the net I found a lot of discussions regarding the quality of Roon DSP volume control.

The discussions revolve around whether it is better to use the device volume, the DAC volume, or
an analogue volume control. One of these threads for example here:
https://community.roonlabs.com/t/better-volumecontrol/126279/13

My concern was to find out the truth about DSP volume control in Roon by measurements just
to know and to let you know.

Please see all the details in the attached whitepaper.

I read:

12dB, to one fourth of the perceived volume
but:
-10dB is about 1/2 perceived volume.
-20dB is about 1/4 perceived volume

-12dB is 1/4 of the signal but not 1/4th of pereceived volume.
 
Last edited:

marcom22

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Excellent work!!!! thanks so much. I quote now for Jriver if it's possible. :)
 
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The final truth about properly implemented DVC is in fact an...old truth (outside the world of audiophile BS, off course).

Anyway excellent work and analysis ;)
 

voodooless

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The discussions revolve around whether it is better to use the device volume, the DAC volume, or
an analogue volume control.

Nice work. However you did not fully resolve all issues. You’ve definitely resolved the digital part, but did not compare to an analogue volume control. Difference is that with the digital one, you are always noise limited to the clean bits a DAC can provide, so about 20 to 22 bits on state of art DAC’s. Analogue volume controls also scale the noise floor. The big question is obviously, does it matter? In the vast majority of cases, it doesn’t, but you can come up with some use cases where is might make a difference. Very high efficiency headphones or compression drivers come to mind.

edit: just saw you mentioned as much in your final words :cool:
 

3125b

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you are always noise limited to the clean bits a DAC can provide
That's what I have found too.
Did a series of simple 1kHz tests at ~50mV with a Windows PC -> Topping E30 -> JDS Atom chain, only using one volume control at a time.
Here are the results:
versuch verstärker.jpgwindows.jpgdac.jpg
With this reasonably budget chain the noise floor of the DAC becomes the (slightly more) limiting part if digital volume control, regardless wich one, is used.
 

JohnYang1997

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Analogue volume attenuates the noise noise of the DAC, digital volume doesn't.
As long as digital volume is higher bit than the actual effective bits of the DAC, it will not add anything bad. There will be no better digital volume.
 

PeteL

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Nice work. However you did not fully resolve all issues. You’ve definitely resolved the digital part, but did not compare to an analogue volume control. Difference is that with the digital one, you are always noise limited to the clean bits a DAC can provide, so about 20 to 22 bits on state of art DAC’s. Analogue volume controls also scale the noise floor. The big question is obviously, does it matter? In the vast majority of cases, it doesn’t, but you can come up with some use cases where is might make a difference. Very high efficiency headphones or compression drivers come to mind.

edit: just saw you mentioned as much in your final words :cool:
Yes, that's assuming optimal gain structure, I admit I didn't fully read yet, but there are definitely use cases where huge digital attenuation followed by high gain will deliver audible hiss, when you have 100 steps of digital volume and you find that it's already too loud at 10%, can't be good, The problem is not the digital volume so much, if you have no other way to control it's a problem, and yes, the main thing is that sensitivity of earphones/headphones are litterally all over the place. Analog volume control are useful gain switches too, sometimes it's the right thing to do.
edit: yes, after reading, the statement is true, even 50 dB attenuation beats the dynamic range of the best amps, but the problem is than there are plenty of situations that you can only use a small fraction of that dynamic range. Bottom line, we all know the conclusion, the basic Idea is this, you'll never attenuate the noise floor with digital attenuation, it will stay fixed, you can just bring the content closer to it.
 
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Branden Fitelson

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thank you -- these questions have been on my mind lately (along with questions about Roon EQ). it's great to see them answered so definitively.
 

phoenixdogfan

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For those who are time-poor, from the paper:

---
Conclusion

The DSP volume control inside the Roon Bridge is as perfect as can be.

The noise floor remains at -178dB, regardless of which attenuation is set for the DSP volume. This means that even at volumes down to -50dB the dynamic at the output is higher as the signal to noise ratio of the best DACs and power amplifiers. No other issues like intermodulation artefacts between the two frequencies or other distortions have been found. The dither is very well done with a completely flat response.

My conclusion is that there is nothing at all to worry about DSP volume in the Roon Bridge. No analogue volume control in the word can deliver these results. The thermal noise of a potentiometer or an analogue ladder attenuator will be much higher than the -178dB the DSP volume control of Roon delivers.

My recommendation: Use DSP Volume whenever possible.[/QUOTE
---

Generally matches the conclusions of other papers I have seen about digital volume controls. :D
Would be nice to know how applicable this is to other software using digital volume controls such as JRiver and Foobar.
 

RayDunzl

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Would be nice to know how applicable this is to other software using digital volume controls such as JRiver and Foobar.

Do you know how a digital signal is attenuated?
 
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