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Analog vs digital volume control - case study with Mytek Stereo192-DSD DAC

Miska

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There has been a lot of discussion about different types of volume controls. For comparison purposes of one case I chose to use Mytek Stereo192-DSD DAC which has three different volume control modes; analog, digital and bypass. Signal routing is implemented using relays. DAC chip is ESS Sabre ES9016S in stereo mode (4 DACs in parallel per channel). ESS Sabre has 32-bit volume control and internal DSP pipeline so it has 8 bits more resolution than allowed by 24-bit external input. It also has higher output level than typical for increased dynamic range. I believe analog volume control chip is TI PGA2311, although the markings on the chip have been removed.

 

DAC was connected to iMac using Apple's Thunderbolt-to-Firewire adapter which also limits input resolution to 24-bit. Measurements were performed from the balanced outputs using typical 3 meter long XLR microphone cable (matches the typical DAC-to-power-amp case). For software volume control case

 

For built-in volume control, three levels were tested; -10, -60 and -96 dBFS. With software control it was possible to also use -120 dBFS setting. Source file is 44.1 kHz 32-bit PCM.

 

TPDF output dither for 24-bit target was used for testing built-in volume control case.

 


 

Results for the analog volume control.

 

-10 dBFS volume setting:

[ATTACH=CONFIG]21702[/ATTACH]

 

-60 dBFS volume setting:

[ATTACH=CONFIG]21703[/ATTACH]

 

-96 dBFS volume setting:

[ATTACH=CONFIG]21704[/ATTACH]

 


 

Results for the digital volume control.

 

-10 dBFS volume setting:

[ATTACH=CONFIG]21705[/ATTACH]

 

-60 dBFS volume setting:

[ATTACH=CONFIG]21706[/ATTACH]

 

-96 dBFS volume setting:

[ATTACH=CONFIG]21707[/ATTACH]

 


 

Results for DSD128 input and external software digital volume.

 

-10 dBFS volume setting:

[ATTACH=CONFIG]21708[/ATTACH]

 

-60 dBFS volume setting:

[ATTACH=CONFIG]21709[/ATTACH]

 

-96 dBFS volume setting:

[ATTACH=CONFIG]21710[/ATTACH]

 

-120 dBFS volume setting:

[ATTACH=CONFIG]21711[/ATTACH]

 


 

Results for 192/24 PCM input and external software digital volume with TPDF dither.

 

-60 dBFS volume setting:

[ATTACH=CONFIG]21712[/ATTACH]

 

-120 dBFS volume setting:

[ATTACH=CONFIG]21713[/ATTACH]



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Miska,

 

I agree with Dennis. Nice to see measurements.

 

So for this layperson with no technical expertise: The Mytek's digital volume control looks like it does a nice job. The -96 and -120 external software settings look like they do a good job also, but hard to see needing those levels of attenuation very often, especially -120.

 

Is that a reasonable interpretation of what we see here?

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Jud,

 

Yes, typical settings would be somewhere between -10 and -60 dB. Those higher attenuations were included to see if the results become "bad" when the level goes really low. I also plotted results for -130, -140 and -150 dBFS attenuation. -140 at DSD128 was still clearly peaking out of the noise floor, while -150 although visible was getting to the level of 50 Hz power supply harmonics and not so clear anymore.

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The digital volume control in Mytek is what is implemented on ESS Sabre DAC chip.

 

It is also interesting that THD is lower at -10 dB level when using DSD128 and software volume than when using PCM 44.1k and the built-in digital volume. I also checked IMD, both PCM and DSD are identical in that respect at 0.00014%.

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Sorry  - I can not see any graphs in the first post  :S


 

In my case i use a Mytek Stereo192DSD Dac, only running in PCM mode 88,2kHz ore more

 i  only have to lower the Volume around minus 10-20dBs

I also use Pure Music on my Mac, so there is a sofware based dithered volume control too...

 

Mr Rob Robinson ( Pure Music developer ) explained for the Upsampling it will be better to use the software-upsampler. That work on 64bit resolution, while Harware-Based Upsampling "only" use max. 48bits, in most case hardware normally run in  32bit resolution.

 

For the Mytek 192DSD Dac Mr. Jurewicz said:

"Analog attenuator is very musical but it does slightly color the sound, albeit less than most preamps."

 

So, what does the digital volume ? is it more transparent, more linear ?

 

thank you in advance !

 

 

 

Edited by 2Control

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