Eliminating Ground Loop in a Rack?

ibanez4life SZ!

Active member
Hey guys!

This is something that has always bothered me...I always try to be really careful when putting together a setup, but I still end up with the same problem.

My most recent iteration for example...I have a head rack combo case that houses my Boogie Roadster. In the rack, I have a power conditioner, GCX, and Boogie Studio Preamp.

Obviously, the power conditioner is sending power to everything. The GCX switches some pedals from in front, A/B's the signal between the Roadster and Studio Preamp, and then does the switching in the loop of the Roadster to either allow the Roadster preamp to pass, or send the signal from the studio preamp in instead.

When I plug the signal cable into the input of both amps at the same time, I get a ground loop. I already have an Ebtech Hum X on the power cable of one of the amps.

I believe my problem to be in the physical rack itself...though I have things isolated from the rails, the rack has a metal 'frame' around the edge that is pretty tight, and touches all the pieces. I have seen many 'pro' rack built like this though, and they seem to get around it.

What is the best way to get around this?

Thanks much!

Eric
 

gbsmusic

Well-known member
ibanez4life SZ!":2rrdfqfp said:
Hey guys!

This is something that has always bothered me...I always try to be really careful when putting together a setup, but I still end up with the same problem.

My most recent iteration for example...I have a head rack combo case that houses my Boogie Roadster. In the rack, I have a power conditioner, GCX, and Boogie Studio Preamp.

Obviously, the power conditioner is sending power to everything. The GCX switches some pedals from in front, A/B's the signal between the Roadster and Studio Preamp, and then does the switching in the loop of the Roadster to either allow the Roadster preamp to pass, or send the signal from the studio preamp in instead.

When I plug the signal cable into the input of both amps at the same time, I get a ground loop. I already have an Ebtech Hum X on the power cable of one of the amps.

I believe my problem to be in the physical rack itself...though I have things isolated from the rails, the rack has a metal 'frame' around the edge that is pretty tight, and touches all the pieces. I have seen many 'pro' rack built like this though, and they seem to get around it.

What is the best way to get around this?

Thanks much!

Eric
You may have run a another Ebtech or a ISP Pro Rack G will also help.
 

glpg80

Well-known member
ground loop exists when you have units that have multiple paths to a single ground source.

idealy, there should be 1 earthed ground connection and only 1 earthed ground connection. using racked gear, sometimes racked units rely on the rack ears to supply the earthed ground for that one unit. other designs utilize a ground plug on the AC power cable (neutral, hot, ground).

if you lifted the grounds of each racked peace of gear by using isolated rack-mount plugs and the design of that unit needs it to supply a proper ground - you can introduce hum this way if the unit does not also have a ground plug (IEC standard)

if you used spacers on the rack gear/screws to isolate them from the metal rack, and all of the plugs are connected to the power conditioner with proper IEC standard plugs utilizing ground prongs, and the power conditioner is mounted without isolation rings on the ears, you should not have any induced hum problems.

what i believe is going on is that you have isolated some gear and not others due to the bar you mention - introducing paths for ground travel because the power conditioner is not isolated like the other pieces, correct?
 

duesentrieb

Active member
What happens if the stuff isn't mounted to the rack but hooked to each other - in a way that the chassis' don't touch each other?
No hum? --> humfrees
still hum? --> Palmer Line Iso Transformers PLI01
 

Ancient Alien

New member
All you need is a single ground in a rack system. Each unit will have a common ground from just the connectors.
I would lift the ground on everything except the main power amp/amp.
I also use Humfrees, and they work like a charm to isolate each unit from one another.
279292.jpg
 

lordriffenstein

New member
Humfrees are band-aids, they don't always are the right solution either and lifting the ground is dangerous and illegal in some places.

Build your rack from the ground up, 1 unit at the time and see when you get hum and then fix it. Then add the next unit.
Do you ONLY have hum if you run into both the head and the preamp? Only 1 connected is ok?
How do you use the GCX? Do you plug into the front or straight into the back?
I'm pretty sure your issue is not with the amps and that Ebtech isn't doing a thing but with the GCX and the a/b-ing with 2 "pre-amps" into 1 power amp.
 

Devilinside

Active member
gbsmusic":i66nfoq0 said:
ibanez4life SZ!":i66nfoq0 said:
Hey guys!

This is something that has always bothered me...I always try to be really careful when putting together a setup, but I still end up with the same problem.

My most recent iteration for example...I have a head rack combo case that houses my Boogie Roadster. In the rack, I have a power conditioner, GCX, and Boogie Studio Preamp.

Obviously, the power conditioner is sending power to everything. The GCX switches some pedals from in front, A/B's the signal between the Roadster and Studio Preamp, and then does the switching in the loop of the Roadster to either allow the Roadster preamp to pass, or send the signal from the studio preamp in instead.

When I plug the signal cable into the input of both amps at the same time, I get a ground loop. I already have an Ebtech Hum X on the power cable of one of the amps.

I believe my problem to be in the physical rack itself...though I have things isolated from the rails, the rack has a metal 'frame' around the edge that is pretty tight, and touches all the pieces. I have seen many 'pro' rack built like this though, and they seem to get around it.

What is the best way to get around this?

Thanks much!

Eric
You may have run a another Ebtech or a ISP Pro Rack G will also help.

I agree, a hum x on each amp should do the trick!
 

Ancient Alien

New member
Zachman":227z7fil said:

Cool info if you don't know about these basics.
But I feel like I just watched 3 Mr Rodgers videos on how to tie your shoes.
Evey electric guitar player should know these basics before ever playing or buying an electric guitar.
 

roadifier

New member
I found that there are ground loops caused by my RG-16 looper, and power conditioner. I usually put hum frees on bot units, and make sure there is a little space between both units so the RG-16 doesnt pick up any noise from the power conditioner (When ever i move the RG-16 away from the power conditioner, I lose most of the ground loop.
 

Zachman

Well-known member
Ancient Alien":m6t3y76m said:
Zachman":m6t3y76m said:

Cool info if you don't know about these basics.
But I feel like I just watched 3 Mr Rodgers videos on how to tie your shoes.
Evey electric guitar player should know these basics before ever playing or buying an electric guitar.

Ya... I have a degree in EE, and understand that most guitarists don't. Many do not understands the basics, and for those who don't, a complicated presentation would likely- not be very well received, nor help to further their understanding.

It was my intent to post those for the info contained in them. (Presentation not withstanding, I hope it helped to serve up the concepts to those who do not/did not understand, in a simple to understand way)

:thumbsup: :cheers:
 

Zachman

Well-known member
roadifier":203sn994 said:
I found that there are ground loops caused by my RG-16 looper, and power conditioner. I usually put hum frees on bot units, and make sure there is a little space between both units so the RG-16 doesnt pick up any noise from the power conditioner (When ever i move the RG-16 away from the power conditioner, I lose most of the ground loop.

That is likely not Ground loop noise, rather it's likely EMI (Electromagnetic Interference), caused by proximity of the power supply lines, and power transformers to the audio lines.
 

steve_k

New member
ibanez4life SZ!":yfsuufph said:
Hey guys!

This is something that has always bothered me...I always try to be really careful when putting together a setup, but I still end up with the same problem.

My most recent iteration for example...I have a head rack combo case that houses my Boogie Roadster. In the rack, I have a power conditioner, GCX, and Boogie Studio Preamp.

Obviously, the power conditioner is sending power to everything. The GCX switches some pedals from in front, A/B's the signal between the Roadster and Studio Preamp, and then does the switching in the loop of the Roadster to either allow the Roadster preamp to pass, or send the signal from the studio preamp in instead.

When I plug the signal cable into the input of both amps at the same time, I get a ground loop. I already have an Ebtech Hum X on the power cable of one of the amps.

I believe my problem to be in the physical rack itself...though I have things isolated from the rails, the rack has a metal 'frame' around the edge that is pretty tight, and touches all the pieces. I have seen many 'pro' rack built like this though, and they seem to get around it.

What is the best way to get around this?

Thanks much!

Eric


Eric,

I have been through this many times running all this stuff. It can be frustrating as hell. Here's a few tips:

Start with the amps. You need to be able to lift the ground on one of them. Your problem will likely go away.

The GCX is not a piece of high end equipment like most people think. Using it for an amp splitter is not very effective, other than the switching.

Your best bet is to get a Lehle P-Split or an RJM Y-Not or other splitter. They both have ground lift and phase inversion. Figure out another way to bypass one amp.

See above. The isolation is just not that good with some pedals. Use just one amp and try and source a pedal that is making noise or one of the audio loops. You can always jump over the loop if it is in the GCX and bypass it. If it is a pedal, well....shit can it if the noise is bad.

Use the buffered input on the GCX.

All wall worts and amps plugged into the same source?

If not using one, get a Voodoo power supply. They are top shelf.

HumX is a piece of shit really. Might be good for a TV or home stereo, but not an amp.

You don't happen to have your lights in the room on a dimmer switch do you? This drove me nuts and I tore a rack apart looking for hum then figured out it was actually the light dimmer!


Steve
 

Zachman

Well-known member
steve_k":2v8mv7ys said:
ibanez4life SZ!":2v8mv7ys said:
Hey guys!

This is something that has always bothered me...I always try to be really careful when putting together a setup, but I still end up with the same problem.

My most recent iteration for example...I have a head rack combo case that houses my Boogie Roadster. In the rack, I have a power conditioner, GCX, and Boogie Studio Preamp.

Obviously, the power conditioner is sending power to everything. The GCX switches some pedals from in front, A/B's the signal between the Roadster and Studio Preamp, and then does the switching in the loop of the Roadster to either allow the Roadster preamp to pass, or send the signal from the studio preamp in instead.

When I plug the signal cable into the input of both amps at the same time, I get a ground loop. I already have an Ebtech Hum X on the power cable of one of the amps.

I believe my problem to be in the physical rack itself...though I have things isolated from the rails, the rack has a metal 'frame' around the edge that is pretty tight, and touches all the pieces. I have seen many 'pro' rack built like this though, and they seem to get around it.

What is the best way to get around this?

Thanks much!

Eric


Eric,

I have been through this many times running all this stuff. It can be frustrating as hell. Here's a few tips:

Start with the amps. You need to be able to lift the ground on one of them. Your problem will likely go away.

The GCX is not a piece of high end equipment like most people think. Using it for an amp splitter is not very effective, other than the switching.

Your best bet is to get a Lehle P-Split or an RJM Y-Not or other splitter. They both have ground lift and phase inversion. Figure out another way to bypass one amp.

See above. The isolation is just not that good with some pedals. Use just one amp and try and source a pedal that is making noise or one of the audio loops. You can always jump over the loop if it is in the GCX and bypass it. If it is a pedal, well....shit can it if the noise is bad.

Use the buffered input on the GCX.

All wall worts and amps plugged into the same source?

If not using one, get a Voodoo power supply. They are top shelf.

HumX is a piece of shit really. Might be good for a TV or home stereo, but not an amp.

You don't happen to have your lights in the room on a dimmer switch do you? This drove me nuts and I tore a rack apart looking for hum then figured out it was actually the light dimmer!


Steve


Amen to this, as a major culprit
 
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