Hello,

I'm using the RCA breakouts that come as standard with the Octo.

This has been niggling at me for a while now so I need to discuss it. When I plug my headphones directly into the dual-phono 'master output' of my DJ controller, the sound is a little too loud for comfort as you'd expect from line-level output.

When I run a stereo-phono -> stereo-phono from the controller 'master output' to ADC1 of the Octo, then launch JACK and connect ADC1 to DAC1:

# /usr/bin/jackd -R -d alsa -r 44100 -p 512 -H -M -S

# jack_connect system:capture_1 system:playback_1

# jack_connect system:capture_2 system:playback_2

ADC1 is at the default volume of '38' in alsamixer (described as 0dB).

Finally I connect the same headphones using the same dual-RCA to TRS-f to DAC1 (at 100% output volume) The sound is much quieter.

Is this expected? I've had some complaints about the lower audio levels and want to know if there's a way to crank it up without introducing distortion.

Yes this is expected. You see the headphones are a low impedance device (16 or 32 ohms) and they require more power to drive them. I assume that the Octo DAC doesn't have enough power to drive them appropriately. It is probably better to use a headphone amplifier IC or something similar for that purpose.

alsamixer exposes 'ADC1 Single Ended Mode' - when I set it to 'Differential', the sound quality is excellent, but quiet. If I set it to 'Single Ended' - the volume increases a little, but the sound is badly distorted.

I assume that there are no other GND connections between the mixers and the Octo is being driven differentially ?

Cheers,

Gavin.

-- 
Checkout the community email list :
https://lists.audioinjector.net/mailman/listinfo/people