Stereo rig hum

[Madlokie]

Hey I’ve been using various 2/3 amp rigs for awhile now and never had issues but a new amp has introduced some pretty loud hum. When i pair my mesa 400+ with my mesa 400 non plus i get some loud hum but the 400+ paired with other amps is dead quiet. Is there a reason those 2 amps wouldnt like being paired together?

 

[agedhorse]

How are you connecting the rig together?

 

[Madlokie]

How are you connecting the rig together?

Using a radial bigshot aby, ive tried all the various switch combinations on the pedal

 

[agedhorse]

Are you using the iso out function to one of the two amps?

 

[Madlokie]

Are you using the iso out function to one of the two amps?

I tried flipping it on/off with no change in the hum

 

[agedhorse]

Then I don’t know what else to try.

 

[hamertek98]

Same guitar? Pedals involved? Wall outlets? Cables? Patch cables? Speaker cables? Gremlins?
So you never had the hum until you brought the 400 non plus into the mix?

 

[Madlokie]

Same guitar? Pedals involved? Wall outlets? Cables? Patch cables? Speaker cables? Gremlins?
So you never had the hum until you brought the 400 non plus into the mix?

Yep and the hum goes away if i switch out the 400 non plus. Same guitar, pedals are involved but i did try bypassing them and the hum was still there but quieter,both amps plugged into a furman power outlet, i could try swapping speaker cables but using the same speaker cable w/ a different head doesnt cause any hum, i knew i shouldnt of fed them past midnight

 

[jeremybnz]

Remove the earth on the lead that goes to one of the amps and see if that helps, usually a ground loop is to blame.

 

[agedhorse]

Yep and the hum goes away if i switch out the 400 non plus. Same guitar, pedals are involved but i did try bypassing them and the hum was still there but quieter,both amps plugged into a furman power outlet, i could try swapping speaker cables but using the same speaker cable w/ a different head doesnt cause any hum, i knew i shouldnt of fed them past midnight

It’s not the speaker cable for sure.

If you remove the pedals entirely (not just bypassing), does the noise go away?

Remove the earth on the lead that goes to one of the amps and see if that helps, usually a ground loop is to blame.

Never remove the safety ground terminal from a power cord, that’s a potentially dangerous condition.

The splitter he is using contains a transformer isolated signal ground lift as part of the signal path.

 

[Madlokie]

It’s not the speaker cable for sure.

If you remove the pedals entirely (not just bypassing), does the noise go away?

Never remove the safety ground terminal from a power cord, that’s a potentially dangerous condition.

The splitter he is using contains a transformer isolated signal ground lift as part of the signal path.

Yea i tried just using the splitter with no pedals before or after and the hum was still there but quieter

 

[agedhorse]

Yea i tried just using the splitter with no pedals before or after and the hum was still there but quieter

Ok, is the amp quiet with nothing plugged into the input?

What happens when you switch the inputs to the amp at the amp’s input jacks? Let’s rule out the splitter itself.

 

[Madlokie]

Ok, is the amp quiet with nothing plugged into the input?

What happens when you switch the inputs to the amp at the amp’s input jacks? Let’s rule out the splitter itself.

Amp is quiet byitself, i can try switching the inputs for the amp when im at my practice space later today however it works with no noise with a different amp combination

 

[agedhorse]

There may be difference in internal ground current routing. This occurs sometimes when combining various pieces of equipment.

Are the pedals on the input side of your splitter?

 

[Madlokie]

There may be difference in internal ground current routing. This occurs sometimes when combining various pieces of equipment.

Are the pedals on the input side of your splitter?

I have a tuner before the splitter and everything else is after

 

[agedhorse]

You are using different pedals on each splitter output?

If you use pedals after the isolated side of the splitter, it may lose the isolation.

 

[Madlokie]

You are using different pedals on each splitter output?

If you use pedals after the isolated side of the splitter, it may lose the isolation.

Ahh i see, yea one amp gets a subharmonic synth and the other side gets the rest of my board. Is there any reason changing only the 400 non plus out would eliminate the hum if its losing the isolation shouldnt the new amp also hum?

 

[jeremybnz]

Never remove the safety ground terminal from a power cord, that’s a potentially dangerous condition.

Oh I wasn't meaning the power ground, the signal ground, if there is a ground loop causing the problem it should quieten things down.

 

[agedhorse]

Ahh i see, yea one amp gets a subharmonic synth and the other side gets the rest of my board. Is there any reason changing only the 400 non plus out would eliminate the hum if its losing the isolation shouldnt the new amp also hum?

The ground current management is different with every amp, an amp that is noisier in one configuration may be quieter in another compared with a different amp.

Oh I wasn't meaning the power ground, the signal ground, if there is a ground loop causing the problem it should quieten things down.

You can’t just lift a ground on an unbalanced signal line, if it works at all, it may result in instability (oscillation) or RF susceptible.

 

[Madlokie]

Is there anything i can do to change the way the ground current is managed?

The ground current management is different with every amp, an amp that is noisier in one configuration may be quieter in another compared with a different amp.

You can’t just lift a ground on an unbalanced signal line, if it works at all, it may result in instability (oscillation) or RF susceptible