giuliomoro shouldn't need to go into a preamplifier with Bela's outputs.
okay, okay, this sounds interesting. Is there an explanation for it? Bela HP output should be capable of loading 8Ohm headphones. Why would 100kOhm preamp be a problem?
Weak, barely hearable. And at the same time covered with immense (probably) white noise.
giuliomoro Is there a ground loop somewhere in the system?
Hmm, lets see. My amplifier is a standalone device, plugged into my home's AC mains. Amplifier GND should be there somewhere. Then my PocketBeagle, that is, Bela, is powered by my laptop, that is also a standalone device, pugged into my home's AC mains. Now, when we connect the two, it seems like the ground loop is indeed formed. Am I getting this right? What would the ground loop cause in this case?