I've installed hifiberryOS on raspberry4 with DAC+DSP and looking for a way to add my subwoofer.
As I can't use channel C and D whitch are added to the DSP programs I decided to use SPDIF for the sub. Is there an easy way to build crossover for chanel A/B and SPDIF (sub) without using Sigmastudio. I'm new to DSP and programming it. I'm just looking for a simple way to build a crossover for 2 chanels and a subwoofer.
I recently got my DAC+DSP board and wanted to do exactly that. I would have modified the DSP code but I don't have the v15 .dspproj file and I have read there are some bugs in v12 with recent hardware so this was not possible. v12 is the latest .dspproj file I have found.
DSP profile channels A/B are connected to both SPDIF and SOUT0 DAC in the default profile. I found a way to connect channels C/D to SOUT0 DAC but they have to be routed through ASRC. Direct connection from DSP core doesn't seem possible without changing the DSP program.
It needs 3 register writes in ssh shell:
dsptoolkit write-reg 61701 0x0002 - this sets up ASRC_INPUT5 register so that ASRC5 uses DSP core as input
dsptoolkit write-reg 61765 0x0006 - this sets up ASRC_OUT_RATE5 register so that ASRC5 uses SOUT0 sample rate
dsptoolkit write-reg 61824 0x002B - this sets up SOUT_SOURCE0 register so that SOUT0 DAC uses ASRC5 as input
Now channels A/B go to SPDIF and C/D go to DAC and you can make a crossover using Speaker Equalizer in HifiberryOS. However there seems to be issue that dsptoolkit store doesn't store these registers so they have to be done again after poweroff or DSP core reset. Maybe they can be put to some Linux initialization file to always run after boot but I haven't done that yet.
SigmaStudio Project files are on Github:
https://github.com/hifiberry/dspprofiles/tree/master/dac%2Bdsp
