I get hum when I plug a 2nd(brand new)mogani cable to play in stereo through my mixer. I don’t think it’s the usual suspect in ground loop. I have a Furman AR-117 for power. MOXF, mixer, and both speakers are plugged into it. I have other stereo channels I’ve moved to that don’t have issue with what’s normally plugged into them and it’s still there. I don’t hear hum in my cans, though. Any thoughts? Thanks, Shep

“Brand new” cables and expensive brand new cables are not immune to carrying ground hum… in fact, they carry it even better than old brand ‘X’ cables - which also carry it, but not with quite the same robust sound quality. You are hearing that ground hum as well as it can sound…

I apologize for my attempt at humor. But ‘New’ has little to do with a ground problem. They do not develop in just old systems or just new systems. Ground problems are immune to age of cables and can be immune to the quality of cables.

Ground issues are usually caused by the interconnection of electrical devices in a system.

You only mention the MOXF, the mixer and speakers… any thing else connected in your system?
Computers are the one thing that would be different from the others. The keyboard, the mixer, the speakers are all built for musical applications. The Computer (bless it’s heart) IS NOT!!!

Disconnect the computer and see if the ground issue disappears… Not that it is the cause, but it is the device that is different from the others. and may need some help sorting out AUDIO.

You mention a second cable. We assume these are standard unbalanced signal cables (TS), Correct?

Yes, sir, both are TS, both are new. I’ve also used some cheapies that I know still work (tester says they all work)and get the same result. The MOXF is the only thing connected to the mixer at current time. As soon as I unplug the right cable from the MOXF, hum is gone. I took everything else out of the mixer (and unplugged) to isolate the MOXF. The pc outs plugged in by themselves in the same channels alone don’t hum in stereo.

Oddly, the MOXF stereo outs connected to 2 mono channels and panned hard left and right don’t hum!?! So I wonder why all my stereo channels hum with the MOXF plugged in?!? Yet my pc does not hum in them, despite it’s build…

I put 4 mono rca to 1/4” adapters on the ends of a stereo rca home audio cable - no hum! I put my ebtech hum eliminator on the right 1/4” output cable, no hum! This is weird.

So I wonder why all my stereo channels hum with the MOXF plugged in?!?

What mixer is this? and what are the channels rated for (what are they looking for as input level?)

I put 4 mono rca to 1/4” adapters on the ends of a stereo rca home audio cable - no hum!

jshep0102 - 21 January 2014 06:28 AM

Yes, sir, both are TS, both are new. I’ve also used some cheapies that I know still work (tester says they all work)and get the same result. The MOXF is the only thing connected to the mixer at current time. As soon as I unplug the right cable from the MOXF, hum is gone. I took everything else out of the mixer (and unplugged) to isolate the MOXF. The pc outs plugged in by themselves in the same channels alone don’t hum in stereo.

Oddly, the MOXF stereo outs connected to 2 mono channels and panned hard left and right don’t hum!?! So I wonder why all my stereo channels hum with the MOXF plugged in?!? Yet my pc does not hum in them, despite it’s build…

I put 4 mono rca to 1/4” adapters on the ends of a stereo rca home audio cable - no hum! I put my ebtech hum eliminator on the right 1/4” output cable, no hum! This is weird.

Do you by chance happen to have the USB cable connected to the MOXF?

USB has disconnected all along - thanks for the thought.

I was trying all cables/options I have to see what could be causing hum. Oddly enough, a simple rca cable with 1/4” adators caused zero hum in stereo… My board is switchable -10/+4. Using -10, not that it changes anything other than the output level. Hums in stereo louder or quieter.

Fortunately playing live I don’t use the mixer for anything but keyboards. So mono channels panned L/R it is. Rehearsals will just hafta hum, as I use 5 of the 6 mono channels for voice.

Thanks very much to both of you for offering assistance. I appreciate it very much, Shep

jshep0102 - 21 January 2014 02:20 PM

I was trying all cables/options I have to see what could be causing hum. Oddly enough, a simple rca cable with 1/4” adators caused zero hum in stereo…

Strictly from a connection standpoint, the RCA with 1/4” adaptors should be the same as using TS cables.

Is the RCA cabling a pair that are molded together over most of their length?

Also, how long is the RCA type length versus the TS cables?

Molded together, 15’ or so long. 20’ TS. TS work great in mono channels.

You need to rule out your mixer as the problem. Borrow or rent another mixer and see
if that is the problem. To further narrow down the issue, I suggest renting/borrowing
a mixer identical to yours, and also a different brand mixer. It could be that the design
of your mixer itself is problematic, or it could be that your mixer has developed a grounding problem or a main output jacks problem.

jshep0102 - 21 January 2014 02:42 PM

Molded together, 15’ or so long. 20’ TS. TS work great in mono channels.

It seems that you’re experiencing some common-mode 60Hz noise which is somewhat different on the two channels. It might be that with the RCA arrangement, the two cables running closely parallel to each other could be minimizing the problem.

Do the audio cables run near power cords? If so, try to keep them separated as much as possible.

What brand/model is the mixer?