When I switch output mode from SDM to PCM - the volume drops significantly. I use pre-amp, HQP volume is always fixed at -4 dBFS. When switching output mode back from PCM to SDM, volume “returns”. I can reproduce issue with two RPI4 images as mentioned above.
For comparison I have tried another NAA configuration:
NAA HW: NUC 8i7
NAA Image from Signalyst: 450 x64ramfs
Switching Output mode from SDM to PCM has no effect on volume, the PCM gain compensation (dB) is set to -6. Works like a bliss.
I can’t figure out if this is a bug or I miss some type of setting.
Holo May USB firmware has a bug that it has digital volume control active in the USB controller. This can be adjusted from the source device though. By default, for safety reasons, Linux kernel sets the volume to -60 dBFS to avoid volume accidents.
Since Holo Red doesn’t have any console access, it is not possible to adjust it from there easily.
Of course solution is to stick to SDM output mode (which is anyway recommended). Another alternative is to use the I2S output from Red to May.
This has the same behaviour though. I don’t know why it would behave differently for you.
But the solution with these is to use the non-ramfs image. Then login as “root” from console, run “aplay -l” to list output devices, then take note of output device number, run “alsamixer -c X” where X is the device number. Adjust the volume to 0 dBFS and then exit by pressing ESC. Then run “alsactl store” to save this for future reboots (for this reason it won’t work with ramfs image, since it is read-only).
But best solution is to get Holo Audio fix the USB controller firmware and disable the digital volume control altogether. Which works only with PCM inputs anyway. This seems to be feature of the newer USB input module model only.
With your kind kick I have checked Kitsune HiFi website for MAY DAC, as I don’t use MAY with Windows I was never looking for drivers there, and Voila!! It looks indeed they have a firmware patch for non changing volume to work with linux devices. Now, need to find an appropriate Win PC to make an update.
As for NUC NAA, i also wonder. Will try to powercycle the whole system to see if I can reproduce once again.
PS: adjusted topic title to reflect actual problem
Yes. 99,9% of the time is SDM@1024x48. Only this time I was after IIR filter which can give a nice analogue twist to things, but @1024 it yet drops out. It works great in PCM.
To close off this topic in case anyone else has similar volume problem with RPI4 NAA (or any other Linux based source) connected to HoloAudio MAY DAC
Solution exists for Gen 2.1 USB only - simply to apply newest (standard) firmware 3144 (Post August20th 2021 dacs ONLY) – it is NOT for Gen 2.0 USB
Here is a quote from Kitsune: This firmware (fixed volume version) addresses a Bug with Linux OS where the volume is at 40-50%, this firmware will address that and apply volume at line level (this was not an issue with windows or mac) This firmware (fixed volume version) is STANDARD as of 11/29/2021
You will need Windows based PC with latest MAY drivers. The firmware update istruction PDF is included into download package. Overall update is a very simple process when you follow it step by step. Hope it helps…
