Well it seems the tip from Paul van der Hulst in the previous project update to use a rpi-dac seems to do the trick. Thank you very much Paul. I think I’m not the only one to say “if only we found out sooner...”.In Volumio open the ‘PLAYBACK OPTIONS’ menu. Under ‘Audio Output’ select for the ‘DAC Model’ the ‘R-PI DAC’ and the ‘Output Device’ should change accordingly (if not select R-PI DAC also). Have a look at the screen dump. No re-sampling is needed now. I tested this setting with 16 bit, 24 bit and 32 bit encoded files and all played perfectly. Save and restart.  

I agree, a permanent solution would certainly be preferable. If anyone knows, as I’ve asked in the original text already, please let us know!  

Hi, II just finished the dac and started by connecting the I2S bus to a scope. Instead of volumio I run moode audio. I found that when the selected device is hifiberry and plain 16 bit CD audio is played, the I2S frame is only 16 bit for each channel 'word'. This is ok for hifiberry, but not compatible with the PCM1794 (the datasheet only shows 16 bit timing diagram for right aligned data, which is an implicit way of saying that 16 bit isn't supported in other modes like I2S) A little googling found that a device called rpi-dac also uses the PCM1794. I don't know about volumio, but moode has a driver for that which is aware of the minimum word length limit of the PCM1794. With this driver the output word is now 32 bit, even for 16 bit data. This is more than the minimum of 24 bits, but that is great actually since it also complies with the limits of the clock multiplier (clock becomes 2.8MHz and the minimum is 2.5MHz). No resampling (processing power) is required, just a different driver. My conclusion is that you should not aim to use the hifiberry driver as a first choice. It is no better than any other arbitrary I2S device. Instead try to find out which device in your distribution matches the elektor DAC closest and continue from there. Paul

Yes, the data signal is present but too weak.

Please have a look at project update 'From the lab: play 16 bit encoded audio permanently'. Please let me know if this works.