ground loop hum?

[rashayritto]

Hey guys. i decided to make some use of my old solid state by getting a Moreley A/B footswitch. The idea was for me to switch between my amps and use them in unison during performances to add a little more flexibility.

when one amp is plugged into the pedal, it sounds fine. as soon as i connect the second amp, the solid state makes an annoying hum that gets really ridiculous at louder volumes. The hum isnt noticable on my valve jr. Is there a way to eliminate this hum besides morley's humX products?

 

[WhoFan]

Re: ground loop hum?

yes...... Radial switchers... they sell ABY units for exactly what you want to do..... the offer models for amp switching between, Tube=Tube, SS=SS, and SS=Tube..... low noise and no ground loops....

 

[Lewguitar]

Re: ground loop hum?

Hey guys. i decided to make some use of my old solid state by getting a Moreley A/B footswitch. The idea was for me to switch between my amps and use them in unison during performances to add a little more flexibility.

when one amp is plugged into the pedal, it sounds fine. as soon as i connect the second amp, the solid state makes an annoying hum that gets really ridiculous at louder volumes. The hum isnt noticable on my valve jr. Is there a way to eliminate this hum besides morley's humX products?

Sometimes you can take one guitar cord and disconnect the ground on one end of the cable only and eliminate the ground loop when playing through two amps.

I've done that sucessfully when using my Kendrick A/B/C box.


Lew

 

[STRATDELUXER97]

Re: ground loop hum?

Sometimes you can take one guitar cord and disconnect the ground on one end of the cable only and eliminate the ground loop.

Lew

Dangerous and risky by today's standards,but sometimes it does work! Ole BF Fenders didn't even have the 3rd prong...Lew remembers! ;o)

 

[Rich_S]

Re: ground loop hum?

Dangerous and risky by today's standards,but sometimes it does work! Ole BF Fenders didn't even have the 3rd prong...Lew remembers! ;o)

Lew said guitar cord, not power cord. Never remove the 3rd (ground) prong from a power cord.

You can disconnect the shield from one end of a guitar cord and tape it off so it doesn't touch the shell of the plug. Then plug that connector into the A/B box. In short, the shield on one box-to-amp cord should be connected only at the amp end. That will open the ground loop.

I do something similar in my pedalboard - there's a switch that disconnects the shield from the output jack to kill the loop between the board and my amp. Works great.

 

[WhoFan]

Re: ground loop hum?

taking the sheild off one of the guitar/instrument cords going to one amp sounds like it would work.... but would it work if you are switching between the amps back and forth? you switch over to the amp with the cord that has no sheilding connection on the instrument cord will it still work?... Or does this set up only work when both amps are on together? Just curious?

 

[WhoFan]

Re: ground loop hum?

taking the sheild off one of the guitar/instrument cords going to one amp sounds like it would work.... but would it work if you are switching between the amps back and forth? you switch over to the amp with the cord that has no sheilding connection on the instrument cord will it still work?... Or does this set up only work when both amps are on together? Just curious?

anyone?

 

[Reckless Abandon]

Re: ground loop hum?

I have a radial Bigshot ABY. LEss than 80 bucks has a ground lift switch on it. I use to marshalls together.

 

[tone4days]

Re: ground loop hum?

can you use one of those "3-prong-to-2-prong" adapters on the AC power cord of the SS amp to fix this?

or is that a different kind of noise ?

i was playing an outdoor gig last year and my carvin turned up noisey ... the stage tech whipped one of those adapters out of his pocket and fixed it up in 10 seconds

t4d

 

[Rich_S]

Re: ground loop hum?

That's the equivalent of cutting off the ground prong - leaving you with no safety ground. Bad idea.

The better way would have been to break a ground (shield) connection between the Carvin and whatever else made up the ground loop, using either an isolation splitter or a special cable with the shield cut.

 

[jeremy]

Re: ground loop hum?

can you use one of those "3-prong-to-2-prong" adapters on the AC power cord of the SS amp to fix this?

or is that a different kind of noise ?

i was playing an outdoor gig last year and my carvin turned up noisey ... the stage tech whipped one of those adapters out of his pocket and fixed it up in 10 seconds

t4d

thats the way i do it when i use two amps, it works and im not dead. having said that, it may not be the safest method

 

[tone4days]

Re: ground loop hum?

That's the equivalent of cutting off the ground prong - leaving you with no safety ground. Bad idea.

The better way would have been to break a ground (shield) connection between the Carvin and whatever else made up the ground loop, using either an isolation splitter or a special cable with the shield cut.

ah - makes sense

the question i am having in trying to visualize the 'broken ground' cable is this ...

how the hell does it even work? ... i mean, we are talking about a low voltage alternating current signal ... so how does the 'negative' side of the waveform complete the circuit if it is cut?

 

[Rich_S]

Re: ground loop hum?

ah - makes sense

the question i am having in trying to visualize the 'broken ground' cable is this ...

how the hell does it even work? ... i mean, we are talking about a low voltage alternating current signal ... so how does the 'negative' side of the waveform complete the circuit if it is cut?

It goes the long way around - through the connected shield to one amp, through its power chord ground wire, through the outlet, and out the 2nd amp's power cord ground to the amp. Not the best path for the audio signal to follow, but it beats a ground loop.

An isolating splitter with ground-lift switches is the better way to go.