The final truth about DSP Volume Control in Roon

[Mulder]

I'm not a technician, and I have some difficulty understanding what's written in this thread. So, if you will, I have a question about something I do not understand as a pure amateur when it comes to these things. But as I understand it, a digital volume control in ROON (or any other program) only lowers the signal strength that leaves the computer or streamer and enters the DAC. The signal-to-noise ratio in the DAC is the same regardless? Or? So the noise floor mentioned in the white paper that started this thread, does it say anything at all about the signal noise ratio in the DAC? Or is the digital volume-control in a DAC just another software volume control, but just in another place than ROON or any other computer software? Or in other words: which is better - a software-based volume control, or a volume control in the DAC? Can that question be answered in the way that happens in the current wite-paper? Can anyone explain in a less technical way how this is connected?

 

[JohnYang1997]

I'm not a technician, and I have some difficulty understanding what's written in this thread. So, if you will, I have a question about something I do not understand as a pure amateur when it comes to these things. But as I understand it, a digital volume control in ROON (or any other program) only lowers the signal strength that leaves the computer or streamer and enters the DAC. The signal-to-noise ratio in the DAC is the same regardless? Or? So the noise floor mentioned in the white paper that started this thread, does it say anything at all about the signal noise ratio in the DAC? Or is the digital volume-control in a DAC just another software volume control, but just in another place than ROON or any other computer software? Or in other words: which is better - a software-based volume control, or a volume control in the DAC? Can that question be answered in the way that happens in the current wite-paper? Can anyone explain in a less technical way how this is connected?

For best performance, get a better DAC with lower noise floor and higher SNR or get a high performing analogue preamp after the DAC.

If the context is limited to digital volume control, an ideal digital volume control needs to have 2 or more bits than the actual measured ENOB of the DAC output. Meaning, 24bit fixed point is good enough. It also means that any 24bit or higher bit dac's own volume control is also good enough.
Even though when you use digital volume control you always lose SNR when you attenuate. An attenuation of 6dB always leads to SNR-6dB.

TLDR, DAC's own volume control is the perfect digital volume control. Add low noise preamp to reserve SNR when attenuate.

 

[bennetng]

a software-based volume control, or a volume control in the DAC? Can that question be answered in the way that happens in the current wite-paper? Can anyone explain in a less technical way how this is connected?

Did you try this?
https://www.audiosciencereview.com/...y-of-software-volume-control.5922/post-172865

 

[danadam]

Kind of a divergent topic, but what is your intuition on 25 bits for floating point? I believe that the IEEE spec is a 23 bit mantissa, 8 bit exponent, and 1 sign bit. That would simplistically give you 24 bits of precision when comparing to something like fixed point. I could possibly see how the lowest exponent bit could be considered an additional bit. Thoughts?

@mansr answer: https://sourceforge.net/p/sox/bugs/292/#3d10

The reported value can be understood as the number of bits a signed fixed-point format would require to represent the the range -1 to +1 with the same worst-case precision. For floating-point formats, the worst precision is at the ends of this range. Starting at +1.0 (0x3f800000), expressing the next smaller value (0x3f7fffff) as signed fixed-point does indeed require 25 bits.
Alternatively, consider the 24-bit signed integer representation. Its maximum value (0x7fffff) as a 32-bit float is 0x4afffffe. The adjacent float values differ by 0.5. It follows that the floating-point format has a precision equivalent to 25-bit signed integer.

 

[bennetng]

@mansr answer: https://sourceforge.net/p/sox/bugs/292/#3d10

I didn't know mansr also answered this. I read the same page before 2020 and only read Robs' answer.

 

[GWolfman]

Thanks.

 

[Dennis_FL]

So I can get Nirvana by Roon-->DAC-->Amp-->Speakers and hopefully not blow up the house fiddlin' with the DSP volume.

I can sell my AVR receiver. What to do with my sub and my Tchaikovsky 1812 recording?

 

[tuckers]

@DrCWO,
Wow, thanks for using my original post on the Roon forum as a jumping off point

Part of the reason to make that post was to prompt discussion about Roon's volume control, as I didn't think they explained the function completely in their support and KB areas.

Since I use only digital attenuation in my system which needs to occur before my DAC, this was an important topic to me. I have the Holo May dac, which has no inbuilt volume attenuation. I also play a lot of DSD files and use parametric EQ for my 100db efficient open baffle speakers. Roon is the only reasonable solution I found that can apply EQ to DSD files without converting to PCM. Using the Headroom Management attenuation (up to -30db) in the EQ also allows me to have some pure DSD attenuation that send the data to the DAC for pure DSD playback. The May plays DSD directly in NOS mode.

The Roon volume control converts DSD to PCM. So I only use it when I need more than -30db. Which is quiet listening at night for me most of the time, and since its at such a low volume, I am less concerned about such things. Just my solution. With PCM files, I'm totally fine with Roons volume control.

 

[voodooless]

Roon is the only reasonable solution I found that can apply EQ to DSD files without converting to PCM.

How would it do that? You cannot do anything with DSD data without conversion to multibit.

 

[tuckers]

How would it do that? You cannot do anything with DSD data without conversion to multibit.

From the Kitsune Website:

DSD IS NATIVELY SUPPORTED FOR THE FIRST TIME ON THIS R2R DISCRETE DAC
HOLO Audio is the world’s first to support DSD natively on R2R DAC, so far the only one. This is not the DSD converted to PCM before digital-analog converter, but directly by the discrete components of the DSD digital to analog converter. Supported currently on MAC (DOP)and Linux (DOP), and Windows/PC (Direct Native and DOP).

https://www.kitsunehifi.com/product/holo-audio-may-dac/

 

[voodooless]

The statement was about Roon, not a DAC.

 

[Mulder]

From the Kitsune Website:


https://www.kitsunehifi.com/product/holo-audio-may-dac/

But why would the DSP in ROON works differently because of this DAC. It must be converted in ROON to PCM. In the ROON DSP

 

[m8o]

My conclusion is that there is nothing at all to worry about DSP volume in the Roon Bridge

Shouldn't it read "... in the Roon Core"? DSP volume is done in the Core, no? Or have I been mistaken all this time? (which is always a possibility)

 

[tuckers]

Shouldn't it read "... in the Roon Core"? DSP volume is done in the Core, no? Or have I been mistaken all this time? (which is always a possibility)

On Roon Endpoints (perhaps not Chromecast or other methods) the volume control is done locally on the hardware, not the Core. However, it is Roon's DSP algorithm on the local device. I have confirmed this with support when I was having issues with DSP etc.

 

[m8o]

On Roon Endpoints (perhaps not Chromecast or other methods) the volume control is done locally on the hardware, not the Core. However, it is Roon's DSP algorithm on the local device. I have confirmed this with support when I was having issues with DSP etc.

Thank you for taking the time to set me straight.

 

[Zenek73]

Hello
To be honest I would feel more safe having physical knob than only tablet controlling volume...
The thred is really complex for me even if I thought I know sth more than usually abut audio
Currently I have cheap active speakers with MF DAC - so I shoulde be worried about such image (green sign of audiophile death)? Only 16b as input data and not very high-end DAC 24/96 (and tbh I believe I dont need sth more bit-rich).

 

[DrCWO]

Green is all OK and far from audiophile death
You always get it if DSP volume is in the signal chain. It only means that the output of Roon is no more bit perfect. You always loose bit perfect output if you apply any DSP. I think this is easy to understand.
The question is how many bits reach your ears? Best current DACs give 21Bits. Applying DSP volume of -12dB means you loose 2Bits out of 24! This is still less than you loose with the best DAC on this planet!
And think of your amplifier. If it is able to deliver 16Bit it will be good. Sure AHB2 from Benchmark delivers more but this is not your scenario.

So no worries about the green dot!
I live happily with it since a long time and I am very far away from audiophile death.

Edit:
If you look at MF MX-DAC review here you learn hat it delivers 17Bit. I don’t know which model you own. So you have seven Bit to loose until you will encounter audible degradation, this is a DSP volume of -42dB

 

[Dennis_FL]

Roon still reduces signal path from lossless to high quality when using volume control under 100%. I use a convolution filter and it also reduces signal path quality in addition to converting DSD to PCM. But as directly above, it sounds great !!!!

I try not not look at the color of the dot.

 

[DrCWO]

Roon still reduces signal path from lossless to high quality when using volume control under 100%. I use a convolution filter and it also reduces signal path quality in addition to converting DSD to PCM. But as directly above, it sounds great !!!!

I try not not look at the color of the dot.

It is a display only
An analog volume control also reduces volume in regard to noise and adds much more unwanted issues.
Please make sure you enabled the Clipping Indicator in the DSP Headroom settings if you use convolution. if it shows a red dot (instead of a green one) you should enter some negative value in Headroom Management to make sure you get no clipping.
Best DrCWO

 

[Tafelberg]

Related question: What happens if I'm using a dac connected to a PC or Mac, and I use the computer's volume control to turn down the volume, while playing a 16-bit file. Does Windows or Mac internally attenuate at 16-bit resolution, or are things upsampled by the OS?

Was this question ever answered? I have the same question... is there any loss of music 'quality' if you use the Windows volume controller to control the volume?