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amp hum
Posted:
Wed Sep 13, 2006 8:16 pmby mark rachelle
here is the situation
ui am running two different amps for my keyboard rig
out of the left side i am using a jc120 and on the right side a be!@#$%^& 90watt keyboard amp
all leads are good and both are off the same circut and power board
why would i be getting hum it happens to either amp
Posted:
Wed Sep 13, 2006 8:45 pmby Simon B
I hope this isnt an insult to your inteligence..... but could it be an earh loop from using different power points? or an impedence mismatch?
Posted:
Wed Sep 13, 2006 9:07 pmby mark rachelle
"all leads are good and both are off the same circut and power board "
including the keyboard
if i plug in the keyboard (a nord stage 88b) into either amp by itself there is no problem with hum
its just a rounder fuller sound with the two amps together
however tghe hum only becomes a problem
when 2 amps are conected to the keyboard at the one time
amp 1 is connected to the left output
amp 2 is connected to the right output
its not a huge problem but its one of those nasty inbetween earth hums
Posted:
Wed Sep 13, 2006 9:56 pmby Linear
The hum comes from a potential difference equalising itself down the audio cables.
Try connecting the chassis of the amps together with some heavy duty cable. Also check that the amps themselves are properly earthed - sometimes 0V on the amp isn't connected to ground, making it a floating 0V (rob correct me if i'm wrong).
If you're feeling really techy, check 0V vs ground on the amp using a multimeter - make sure there is no potential difference there.
Chris