Originally Posted By: Lawrie
Originally Posted By: Ryszard
My DAW is a full tower PC with a self contained power supply. It is shielded on all sides but the bottom.

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I'll assume it is a normal steel case so the bottom will also be shielded by the metal of the case which is grounded through the PSU


No. Unusually, it's open on the bottom as an air intake. Weird.

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I'll have to check on the type of ceiling light in my room. How do you do an earth/ground lift on a USB line?

You don't, it would have to be done in a common signal path somewhere.

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There is a Cat 5 Ethernet line running through the rat's nest behind my studio desk. Could that be a source of interference?

Anythng is posible, but I doubt it. You are talking RF signals of more than 10MHz. Actually it's probably at least 100MHz.

Something you might try:
leave the Presonus plugged in on the audio side, but UNplug the USB cable (I assume it doesn't use the USB cable for power?)

Hmm, thinking about a ground lift on USB, if the Presonus IS externally powered it might be possible to disconnect the power wires in the USB cable at one end. Only possible downside is if the USB interface itself needs to be powered by the USB cable...


The AudioBox receives both signal and power via USB.

"My primary musical instrument is the personal computer."