Volume Control

[tc-fi]

Hey guys.

I'm wondering how volume control is implemented. When I tested the RuneUI volume control settings, I got the results below. I'm using an ODAC which does not contain a hardware volume processor.

None
- RuneUI volume knob disabled
- Alsamixer volume functional

Hardware
- RuneUI volume knob functional
- Alsamixer volume control functional
- RuneUI volume knob and Alsamixer volume control are directly coupled. Change one and the other changes.

Software
- RuneUI volume knob functional
- Alsamixer volume control functional
- RuneUI volume control and Alsamixer volume control operate independently of one another

What's happening where RuneUI volume control is coupled to Alsamixer volume control?

Also, for 16 bit samples, is dither being applied after volume processing? If not then you should consider integrating a high quality dither algorithm. No need for dither if 24 bit samples, only 16 bit.

Regards,
tc-fi

[ACX]

[tc-fi]

What's odd in my case is that my JDS-Labs ODAC does not contain a hardware volume control, yet I am using the "Hardware" MPD setting and it is working as described in the comments. This suggests that ALSA must be doing volume in software.

So my question is does ALSA volume control algorithm also apply dither?

[ACX]

[tc-fi]

The ODAC is based on Sabre ES9023 DAC chip which does not contain integrated DSP ( volume control, filtering, de-emphasis, etc.), and there is no external DSP chip in the ODAC which could do volume control.

Sabre does make other stereo DAC chips for example ES9012 which does contain integrated DSP for volume control. Comparison below::

Sabre ES9023
http://www.esstech.com/PDF/ES9023%20PB% ... 110117.pdf
Sabre ES9012
http://www.esstech.com/PDF/ES9018%20ES9 ... 0Brief.pdf

[ACX]

[tc-fi]

I had read the Tenor datasheet before, and perhaps due to the wording, I concluded that the integrated volume control on the chip operated only on the SPDIF interface.

But it also must operate on the USB interface since I'm in fact getting an alsamixer volume control, and as you point out, alsa is acting only on the interface.

Thanks!

[ACX]

You are welcome, happy to clarify that point