WTF/Help - ground loop?

[Hamner1]

The problem is only when I am using a particular guitar. I recorded a 25 second clip that hopefully demonstrates my problem.
1st 5 seconds is Jackon King V with EMGs - I don't have the problem
5-10 seconds = Hamer Sunburst Archtop with Duncan Design pickups - I don't have the problem
10-15 seconds Jackson DXMG with EMGs - I get the noise
15-20 seconds I touch the volume knob on the DXMG & the sound/noise diminishes substantially (I don't think you can hear it on the clip). Last 5 seconds I take my hand off the volume knob & the noise returns.
All of this was done with the volume on the guitars turned off/0

I thought maybe the power amp or the RM4 or the cord. Used a different cord and same problem as above. I would think if it was the RM4 or Power amp it would be an issue regardless of the guitar I have plugged in. Local Tech checked ground on this guitar a couple weeks ago when I had it in for a neck adjustment.
Any thoughts on what is causing this.

Here is the clip
http://www.soundclick.com/player/single_player.cfm?q=hi&songID=9651521

 

[HughJasol]

The DXMG is used to own had EMGs, but they were EMG-HZ passive pickups, not active. Is that what you have?

 

[Mattfig]

Sounds like the guitars themselves...Can you just try 'em in a mixing board or another amp and redo your experiment....My hunch is that the results will be the same...I don't think it's cables, cords, etc....Just the nature of the beast....I have lots of guitars and some are just naturally noisier than others for countless different reasons...Just my $.02...My advice that would easily remedy this problem...ISP Decimator G-String Pedal...It was built for problems like yours and works seamlessly and does NOT affect tone...I have one myself and no longer have issues like yours...

Best of luck!

 

[muudrock]

This is simply a grounding issue in the guitar electronics, not the amp. If you touch metal on the guitar and the buzz gets noticebably less, you are acting as the ground. This is an easy fix, just need to find where the ground is open in the electronics cavity. Check that all the pots are grounded together and that the pickup ground wire is soldered to ground on the back of the volume pot.

**Edit**
Might want to take it to a tech if your not sure what to look for.

 

[Julia]

I'd say you have a bad pot in your guitar or your ground wire is loose or a pickup is shot.

 

[Hamner1]

Thanks for the info all. What I also thought was odd is if I touch the RM chassis (fiddling with tone pots, volume, etc) it also lessens the noise. I suppose it is the same principle in that I am acting as ground it is just at another spot in the chain.

Still probably a good idea to get the Decimator pedal even after I get the issue on the guitar resolved. Do you run that in the loop or in front of the amp. I'm thinking Guitar -> Decimator pedal -> Volume pedal, etc -> front of RM4.

 

[Mattfig]

Thanks for the info all. What I also thought was odd is if I touch the RM chassis (fiddling with tone pots, volume, etc) it also lessens the noise. I suppose it is the same principle in that I am acting as ground it is just at another spot in the chain.

Still probably a good idea to get the Decimator pedal even after I get the issue on the guitar resolved. Do you run that in the loop or in front of the amp. I'm thinking Guitar -> Decimator pedal -> Volume pedal, etc -> front of RM4.

Well, if you go with a Decimator, spend the extra bucks and get the G String version...It is amazing...It has a guitar input for the front end and then you can place the actual decimator later in the signal chain...That's what makes it so functional and unique...It is truly the best noise reduction system I've ever come across...

 

[Julia]

Thanks for the info all. What I also thought was odd is if I touch the RM chassis (fiddling with tone pots, volume, etc) it also lessens the noise. I suppose it is the same principle in that I am acting as ground it is just at another spot in the chain.

Still probably a good idea to get the Decimator pedal even after I get the issue on the guitar resolved. Do you run that in the loop or in front of the amp. I'm thinking Guitar -> Decimator pedal -> Volume pedal, etc -> front of RM4.

Well, if you go with a Decimator, spend the extra bucks and get the G String version...It is amazing...It has a guitar input for the front end and then you can place the actual decimator later in the signal chain...That's what makes it so functional and unique...It is truly the best noise reduction system I've ever come across...

And I'd go with the rack mount Decimator G unit.

 

[Hamner1]

quick update. didn't bring the guitar & rack in to have everything checked yet. However I did decide to plug into my practive amp (Vox solid state Valvetronix VT30). No issue with the noise. My guess is because it is a solid state circuit (or it has some noise suppressor in it).

 

[eedude]

...I touch the volume knob on the DXMG & the sound/noise diminishes substantially (I don't think you can hear it on the clip). Last 5 seconds I take my hand off the volume knob & the noise returns...

muudrock is on the right track...

The ground on a guitar is connect to the stings, the pot case, and the output jack. If your stings are not grounded you will get that hum or buzz. The fact that when you touch the pot and it goes away is pointing towards a faulty ground to the stings. If you have a floyd the connection is back where the springs are. Inspect that connection at the springs and where that wire connects in the control cavity. If you have an ohm meter measure the connection from the ground of a guitar cord to the strings, see if they are disconnected.

 

[Julia]

Wow. Use a meter? Who'da thunk it? :lol:

 

[Hamner1]

Wow. Use a meter? Who'da thunk it? :lol:

a meter... is that there some new fangled spaceship technology. :lol:

I plan to bring the stuff in tomorrow to have it checked out.

 

[Hamner1]

Well I brought my rack into the music store today to see if I would get the sound result/issue. Low and behold no issue. :x It wasn't even a case of the noise was substantially reduced, it just wasn't there. As you can guess this kind of pissed me off, especially since the rack is bulky & not light. The tech & I think maybe it has something to do with the wiring/ground in the house, or something that is being introduced in the room the amp is plugged into. With that thought I decided to move the rack out into a different room & try some different outlets. Guess what the noise is back when I roll off the volume.

:idea: I figured if I use my volume pedal & roll the volume all the way off I should get the same issue. No issue (guitar volume cranked, volume pedal off/no signal going to amp). I'm convinced it is the guitar, I just can't figure out what is causing it & why it would not reproduce the same results in the music store. :?

Here is the deal I usually use the volume pedal with the master knob set to roll off a little volume when the pedal is heel down all the way. I Use it this way for my cleans to prevent clipping the front of the module & take off some of the brightness away. I want to be able to turn the volume off inbetween songs while on the dirty channels & avoid the noise, which with the pedal I have means turning the master knob all the way off so heel down is no volume. This then messes with the ability to use the pedal on my cleans as I like. Yes I could manage to finagle the rocker pedal partially to achieve the same result as using the master volume knob on it, but that is a pain when it is just easier to heel fully down to produce the desired result.

Shoot me some ideas.
* Invest in another volume pedal or the morley volume pedal that has the master knob activated by a footswitch?
* Some type of on/off footswitch to run before the preamp?
* Decimator G string pedal or Rack unit (from the reviews it sounds like this should work)?