60 cycle hum -HELP!

Don Anderson

Well-Known Member
Here is a video describing my routing and 60 cycle hum. Tried everything mentioned as well as humbuster cables, unplugged everything from the loops section of the PBC going to my Amps Loop (one by one, then all at the same time removed) -still happened.

Still happened unplugging the input to the front of the amp, But is gone when I unplug the Send/return cables from the amps loop

Help!!

.
 
If you aren't using Output B on the PBC to connect to your amp, switch to using Output B, then turn on the Iso B switch on the rear panel of the PBC.
 
@rjmmusicI am not using OP B it's the left one, I think it's says 'OP Left A/B'
Awesome I will do that tonight!!! Can you elaborate on what that does and why it started this hum once I added the Nemesis?
 
The Nemesis, one way or another, is creating a ground loop. Or, it's making an existing ground loop worse. Switching on the isolation transformer hopefully will break the ground loop and get rid of the hum - that's what it's for. Typically, it's needed in a 2 amp system, but you can definitely end up with a ground loop in a 4 cable system as well.
 
RJM covered it well as usual. I think another good option is to have a ground lift cable as a solution or even for a quick test (if you didn't have the iso transformer in B. This can remove the use of running through a transformer while removing the additional ground which is creating the problem. Build a TS cable as normal on one side...the other end has only the signal attached (tip), the ground wire is lifted from the sleeve. This cable would go on the last effect that is creating the additional ground point. You're only doing this in points that create additional grounding problems...removing all ground give you terrible results lol.

The grounding issue is probably at your power amp input section (FX return).
 
Last edited:
OK so output b n the iso b button did work!!!!! Took a 2nd try for some reason, it was like it kicked in. STOKED, now I can play guitar and program my midi delay presets!
@rjmmusic @Diezel Thanks!!!!
 
Last edited:
I never heard of it as a hum buster cable, that's just a name that someone made for it..but it works as the name if you like :). The normal ground path is: guitar- preamp-power amp-ground. What you have now is more then one ground path which is creating the noise you're hearing...So you need to break one of the duplicates to stop that hum. Breaking that path can be accomplished by a transformer or ground lifted cable on one end. Sometimes one method works better then others. It's trial and error.

Wherever that last cable you connect stops the hum, that's where you can try a ground lifted cable. Put the ground lift side on the last component that creates the hum. For example, if you unplug the fx return and the hum stops, that's the last wire in the chain that would be completing your extra ground loop. Put the cable in that spot...and the lifted side plugs there. There's a variety of transformers you can try too...it may be a couple of areas creating the problems. Ebtech makes an inexpensive 2 channel model which work well. Me...I try the ground lift cables first...then try transformers. Sometimes a ground lifted cable, depending on the location can create other interference problems.

Another area to look into is cable RFI interference. I"m sure what you're experiencing is a ground loop first and foremost...but there could be other noise you're adding. I've even seen problems with some main brand power bricks where RFI interference based on proximity is a problem I won't post names in here from the ones that I didn't care for...but some really were proven bad performers from experience. Keep power cables away from signal cables...when the cross paths, keep them perpendicular...avoid close proximity parallel runs of those two types. Some people deal with the grounding noise and use a noise gate i.e. decimator (I use a rack mounted decimator pro g)..but you really want to remove ground noise and other interference first. Hiss and things like that are usually inherent from high gain amplifiers. For example, my Friedman BE100 at high gain levels is quite noisy (hiss). The only thing to help that is the Decimator.
 
"Humbuster" is a term Fractal Audio made up for impedance balanced cables. They have TRS on one end and TS on the other. They only work with equipment that's specifically designed to use them (i.e. the Axe-Fx).

Ground lifted cables are something different, but if an isolation transformer doesn't work, a ground lifter cable probably won't either.

Maybe a better approach is - what do you have to take out of your system to make the hum go away? Does removing the Nemesis do it? If you are sure of where it's coming from, then it's easier to focus on a solution.
 
I wasn't aware of that name Ron, thanks for the clarification. I missed Don's first comment where he attempted to use a ground lift cable...I see it now though.
 
Back
Top