[How to do instruction] DSD to PCM on-the-fly conversion sample rate setting

[4mayday]

Hi all,

Is it possible to set certain sample rate fot DSD to PCM on-the-fly conversion? 
Default sample rate is 352.8 kHz.
But my audio shield Pi2Design 502DAC supports max 192 kHz. No DOP, no native DSD through SPDIF on my external DAC.
So I have to use DSD to PCM on-the-fly conversion and I need the sample rate to be 88.2 kHz (because 176.4 files plays on 502DAC with crackles, I don't know why).

[Tim Curtis]

You should be able to set SoX to whatever rate you need in MPD config.

[swizzle]

@4mayday

Not really moode related, but... I don’t know if it’s an ongoing thing but the 502dac had an issue where the legs of the pins for one of the outputs (bnc I think) could end up too close to the usb shield on some boards and this manifested as interference in higher bitrate files, the fix was to snip the tips of the protruding legs to provide more clearance though you should probably contact them to make sure. See this thread for particulars, Michael Kelly there is the designer/manufacturer.

https://www.superbestaudiofriends.org/in...ost-129885

[4mayday]

You should be able to set SoX to whatever rate you need in MPD config.

AFAIK if I set SoX - it will convert everything. I need to change sample rate only for DSD to PCM on-the-fly conversion. Is it possible to restrict the sample rate to 88200 Hz?

[rhizomusicosmos]

@4mayday

As I understand it, the Pi2Design 502DAC uses the Hifiberry DAC+ Pro kernel driver. This driver allows up to 384 kHz sample rates even though the hardware support may be flaky at such high rates. So the kernel driver is reporting that it is capable of 352 & 384 kHz to ALSA/MPD and therefore the output of the DSD2PCM module, which is fixed at 352.8 kHz, is not being resampled before being passed to the output.

From your original post, it appears you are using the 502DAC to output SPDIF or AES to another DAC. Is that right?

So what you want to do is fix an upper limit for sample rate compatibility to 192 kHz or maybe 96 kHz if you are having issues above that.

@Tim Curtis Can an upper limit be set in an ALSA config that overrides the kernel driver? I'm making the assumption here that ALSA is doing the SRC not MPD (libsamplerate).

[4mayday]

@4mayday
From your original post, it appears you are using the 502DAC to output SPDIF or AES to another DAC. Is that right?

Yes, I use 502DAC, output SPDIF (BNC) to external DAC. 

Actually I need DSD to PCM on-the-fly conversion to be exactly to 88.2 kHz, because my external DAC does not support 176.4 kHz.

[Tim Curtis]

MPD sources would need to be modified to expose a new setting that allowed a particular SoX rate to be applied only when MPD is performing DSD to PCM on-the-fly conversion. Its not something I can control in moOde.

You could propose it as a feature in MPD Git repo.
https://github.com/MusicPlayerDaemon/MPD/issues