GPIO expansion boards and DAC+ Pro

I have a HiFiBerry DAC+ Pro, which outputs sound beautifully when seated directly onto the GPIO pins of a Raspberry Pi 3B+. However, when I use either a GPIO expansion board or a breadboard (with nothing else connected), there is no sound output.

Is this to be expected? I'd appreciate any tips or advice.

In all cases:

• the DAC draws power, with the green status LED lighting up

• 'sndrpihifiberry' is picked up as card0 by ALSA

• alsamixer reports 'Digital' is unmuted, and at 100% (207)


I can't notice any difference either way - except the lack of sound if the DAC+ isn't connected directly.

I'm powering the card via the rPi - I haven't removed the 0Ω resistor or connected a 5V supply to the DAC. The Raspberry Pi is being powered over USB, with a reliable 5.1V 2A transformer from mains power.


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