Hum in my rack!

[Bullen]

Hello everyone!

I got some questions for you rack gurus.

I´ve been putting together my new rack rig over the last few days and when most of it was connected, and I took it for a test drive, I noticed a pretty bad hum.

The rig is quiet until I turn on either the rack mounted dbx compressor, or when I switch to my Mesa Mark V head with a Mesa amp switcher, controlled with a gcx. My Mesa Roadster head is pretty quiet, but there´s a slight hum to it aswell, but on the Mark V it´s pretty loud.

The signal chain so far is as follows:
guitar
-gcx guitar in
-loop 1 dbx comp (Hums)
-loop 2-mxr phaser (quiet)
-loop 3 mxr flanger (quiet)
-out of loop 3-input of Mesa Ampswitcher
-amp send 1 to the Mark V and amp send 2 to the Roadster.
A TC electronic M-One is connected to the fx loop one the Mark V. The rest of the gcx loops are used to control the channelswitching on the heads and the ampswitcher.

I have all the powercables (rack and heads)connected to the same outlet, but it´s a bit of a cable jungle in the back right now. Can that be the cause of the hum?
The signal chain cables are pretty mutch cut to length, but not the powercables. I will tidy it up a bit more, but I want everything working before I do any more permanent wireing.

It seems that when I put the devices in the rack I get the problems. Before I put the ampswitcher in the rack I had it on a shelf and I didn´t get any hum when switching or combining amps. The Dbx compressor was also quiet before.

So what do you guys think? Ground loops or what? And what can I do to solve this problem?

Any help is appreciated!

Thanks!

 

[RectoStudioGuy]

Perhaps ground loops. Also, have you segregated power from signal cables?

 

[Martin]

I had the exact same issue with my system. It was totally quiet untill I put in the switcher and then it was a fucking nightmare !
I did manage to sort it though. I started by using some hum-free's on each piece to isolate each component from the rack and each other....didn't do much but left them in.
Then I bought an Eb-tech ground hum eliminator and pluged it into my MKIII power cord, that cut the hum substantially. Next I cut all my power cords to the length needed in the rack and routed them away from any signal cables as best I could, this helped also.
I still have a little hum but I can deal with it. The other thing is that I noticed a lot of noise is actually coming through the pickup's themselves just from RF in the room, even through humbuckers so I will be getting an ISP Decimator just to put in front of the guitar input to clean it up a little.

One other thing I did was I bought a Monster power conditioner, what this did was give me way better dynamics by dropping the noise level down and cleaning things up...I now have better resolution on my stereo sound stage.

Hope this helps ?

 

[RectoStudioGuy]

You might also want to look at what else is on the circuit, primarily the neutral, with your rig. I'm sure you've noticed that plugging into some power sorces seem to be better than others? Electronics, computers, tv's, etc. are noisey and create harmonics (not the good kind) as well as transients that travel your current path back to the panel.

There are so many different origins of hum that you just need to work the issue one piece at a time.

 

[Malin]

My rig has been very well built but the hum and hiss was really bad. I bought an ISP Decimator ProRackG and voila

 

[Bullen]

Thanks for all the replies!

I haven´t really had the time to got through the rig, but I did try the ampswitcher without the gcx. And I got no hum/buzz then. Will go through the rig this weekend.
Hopefully I will be able to find the problem and solve it.

 

[ibanez4life SZ!]

The Mark V is in a ground loop because of the T.C. M-One. You can either isolate it better in the rack, or get an ebtech hum-x for the Mark IV. Up to you.

As for the compressor, there is probably something similar going on...are you powering it directly off the same power strip? Probably another ground loop between its power source and the rack.

PM me if you want some more help, but I'm sure I can get it figured out for you.

Eric