Benchmark DAC1 pre USB - seems to stay at 24bit 96khz regardless of input file

Im thinking of subscribing but am currently having some distortion issues which I believe may be due to forced resampling. Any files I play whether 16bit/24bit 44.1 - 96khz seem to have some distortion which I believe may be due to some sort of forced resampling when connecting via USB to the Benchmark DAC1 pre Is there any way to check what the usb DAC is accepting from Volumio via ssh while a song is playing and if it changes based on the input file ?

G

There is a Audio Resampling option under SettingsGeneral Playback Options

But I thought it was off by default

Audio resampling is off as is the software volume mixer (trying to get bit perfect output)

I have 2 Volumio instances

1 raspi 3b running latest version from website
1 intel compute stick running latest buster beta x86 as I’m going to recase this to build a sexy streamer

Both using WiFi with no issues

Same issue in both Would be interesting if I can find out what Volumio syncs to with the DAC over usb As it Seems to be complex music that is distorting leading me to believe the DAC is only syncing at 96khz and non 96khz songs are being updampled causing this distortion. (The Benchmark DAC1 pre has no indicators to say what bitrate it’s syncing to

I have an HDMI stripper arriving soon so I’ll check the output using coax and toslink to see if it’s just a usb issue with Volumio and this DAC

G

I just went to web, here is an example.

Upsampling? | Stereophile.com

Apparently the DAC 1 is an upsampling DAC!

Edited

I did further reading. The Benchmark DAC is an old design. The USB interface runs in synchronous mode; the I/C clock is determined by the host i.e. the device running Volumio. The DAC1 upsamples to a fixed local clock. It is supposedly good at de-jittering the I/C signal but there are probably limits to what it can handle.

From owners manual of DAC1 Pre

“ The USB input supports 44.1, 48, 88.2 and 96 kHz sample rates at word lengths up to 24- bits. The USB interface acts as a ‘native’ USB audio device and does not require the installation of any custom drivers.”

I have confirmed this using my MacBook Pro outputting to the usb audio interface with same files. With no distortion and the sync happens at the correct bitrate/word length

Seems to be an MPD/Volumio issue with the BenchMark DAC1 or something I’m unaware of

Cool. I will await my HDMI audio stripper so I can feed it pure Digital to the TOSLINK / COAXIAL rather than using the USB interface. BUT the puzzling thing is when I connect my MacBook via the USB interface and select the output bitrate to match it to my source audio files I don’t get any of that distortion. thats what led me to think Volumio was just spitting the signal out at 24 bit 96 kHz regardless of input bitrate / sampling rate. Also I can reproduce the distortion by playing an 88.2khz file at 96khz output sync through the USB on MAC.

Most USB DACs now run in asynchronous mode. The asynchronous USB DAC controls the host clocking so it avoids the jitter problem. The MacBook may well be superior in synchronous mode; I do not know much about Apple generally.

I will await my HDMI stripper (hopefully volumio outputs the bit perfect stream to the HDMI interface. this WILL solve my issue ?(was only using the USB interface as a last resort :wink:

Thanks for the replies

G