Hi lenny stein.

Sounds like you may be getting a ground loop with that connection. Does the amp have a grounding port on it (similar to a DJ mixer)?

I'd also make sure the cables you use are not near any power strips, power plugs, and try to keep the placement of the cable as far away from any amps or speakers as your setup allows.

Also try it on another power point in your house/venue. The wiring may be faulty.

btw. if you didn't read casket hand's suggestion in your other post, make sure you mute the mic and aux input too.

Hello Matt,
I moved the set-up away from a power strip and this did decrease the hum to some degree - I believe the VCI 300 does not have a mute button for the aux in (through) and mic ? but I did turn these knobs down as well - I am using good quality cables and the powered speaker I am going into is very good as well - there is a polarity switch on it ( made no difference) but no grounding port - Are the quater inch main outs on the VCI 300 balanced? - I seem to get much less noise coming out of the VCI with an unbalanced (RCA) cable - Again I don't seem to have a problem when I jump the VCI 300 to a larger mixing board ( rane mp44 or AH zone 92, but obviously, I'd rather not to take extra gear with me for small applications

Can you select the MIC/AUX panel and mute - as shown in the attached picture.

No, the VCI-300 outs aren't balanced, so use unbalanced cables when testing.

Make sure you wiggle the powered speaker power plug on the outlet socket side to ensure it has grounding to the ground plug (the 3rd prong). Swap the power cords if you can also (like borrow a plug from your desktop computer) See if it works.

possibly slightly off topic, but while we're talking about the VCI's outputs....

Are the 1/4 inch jacks at the same level as the phono's/RCA's?

I'm just wondering if i'll get a hotter signal by using the jacks.

The outputs are both the same level.