[linux-audio-user] Pre-Amp hum (related to jack, somehow)

The irony of this is killing me. I had a singing capacitor in my notebook computer, which I was able to solve using a load generator at a low scheduling priority. However, that same capacitor is what had triggered me to get a higher-end sound card in the first place. Now this higher end sound card has quite a loud hum when the phantom power for its mic pre-amps is on. Interestingly, when I mix the signals from both pre-amps by connecting them both to the same outputs in JACK, the noises from the Mics cancel each other out. The load generator has no influence on the hum; however, the sampling rate does. The higher the sampling rate the higher pitched the hum is. The inverse is true for buffer size: The larger the buffer, the lower pitched the hum. My current theory is this: Jack causes a surge of power in the CPU through an interrupt. This surge gets transformed into current in the grounding cable through electromagnetic induction, which in turn induces a current in the microphone pre-amps, which causes the hum. The hums can cancel each other out because... uh, not the slightest on that one. Help appreciated. Carlo