Eliminating hums and ground loops

I don't normally publish an email someone has sent to me, but this response from the Lexicon support team was extremely helpful. I thought I'd share what Ryan says about tracking down a ground loop.

Peter,

You may be experiencing a ground loop in your system, if so you may want to try to find which component is causing the loop. Typically a ground loop will cause hum in a system; however, since the Alpha is a USB device the data transfer signal may also be heard.

Try disconnecting all devices that are connected to your Alphas inputs and outputs then connect a microphone and a pair of headphones. If you hear the hum sound at this point there may be other issues aside from a ground loop. If the hum is not initially present, connect one device at a time to the Alpha to see if you can find the component that causes the hum.

If you are able to find which piece of equipment is causing the ground loop you may want to use an isolation transformer or hum eliminator between this piece of equipment and the Alpha.

Does this same noise occur when you connect to the instrument input on the front of the Alpha with an unbalanced cable? Does the noise occur even when a passive device such as a guitar is connected to the Line 1 or Line 2 input?

Let me know if you need more help.

Regards,
Ryan Hauschild
Lexicon Pro Support