L2m HUM USING MIX OUTPUT

[ddufour]

Maybe I'm wrong but can't you connect the MIX OUT to an input channel

on your mixing board, and get the same tones from the L2m going to the pa?

When I connect that way and turn the pa on, I get a very loud hum like something

isn't connected properly.

What I am trying to do is run my pedal board to the L2m and use that as my own

monitor, then run that sound to the pa to be turned up or down with the mix.

[SiWatts69]

What you're most likely experiencing/hearing is a ground loop hum.

 

These hums occur when the ground connections of two *powered* items which are connected to the same mains supply but where there is phase shift between the two earth outlets (or summat like that). Common where the two mains outlets are on different circuits but with a shared earth or where the two outlets are on the same circuit but a distance part from each other.

 

To get rid of the hum, you need to isolate the two powered items from each other. This is achieved typically by using a DI box OR 1:1 line isolator.

 

In items where they are intended to be connected in this way, the isolation is often built into the device eg bass amps/cabs often have DI outs. BUT it would not be expected that you'd connect a foh pa speaker's signal out to a desk directly. Desks most often don't have isolation on their inputs.

 

You'll commonly hear hum if you connect the line level output(s) from a keyboard directly to the M20d. It goes though if you insert a DI box into the chain. The DI box also converts the keyboard's unbalanced signal to a balanced one.

 

You need to either run a line isolator on the speaker mix out.

OR

Run into a DI box from your pedal board, running the "thru" on to the L2m and the balanced output to the M20d.

[ddufour]

Running a DI box between the L2m and the board took care of it.

Thanks