Weird ground loop hum with my budget modelling solution

Dave_Vader

Before I start, I already know the answer is to just suck it up and buy the HX Stomp XL that I actually want.

However, on my journey towards that (and saving the money to get it) I bought a NUX Amp Academy, and put it in the FX loop of my HXFX, whereupon it makes an almighty hum as soon as I apply gain. The same thing happens if I put the HXFX in front of the NUX, like I do when I run it into a normal amp.

BUT

(And this is where it gets weird)

If I put the HXFX in the loop of the NUX, no hum, everything sounds great. 

But there are way less routing options for the FX this way. I've got saved "steps" (like a snapshot) in the NUX to shift the loop to before and after the amp stage, which is an okay, if tap-dancy, workaround for now (unless I'm in the mood for amp gain, compressor and subtle delay/reverb). But does anybody have any idea why it's doing this? 

I've tried both FX loops in the HX, and using separate sends and returns over just the loop.

It's very weird, and makes no sense.

Benz3ne

Have a look at the Nux AA user manual - it mentions something about toggling either the DI or Out switch on the rear to help eliminate ground loop hum. Might be of absolutely no use to you, but it might help?
I recall reading about it last night, coincidentally, even though I'm having no such issues.
Good luck! 

Dave_Vader

Yeah. I tried the ground lift switch. It didn't help. Good idea though. I'm going to hunt through the global settings on the HX next.

Dave_Vader

There's also a weird phasing thing going on with my workaround now, so I may give up.

borntohang

What do the power supplies look like, and have you got the I/O levels on both devices set appropriately? Would probably need setting for Instrument on the HXFX and whatever the equivalent is on the NUX.

Dave_Vader

Yep. Had it all set like that. And the cheap chinese 1A power supply was noisier than when using both my line 6 3A power supplies at the same time, but not silent.

I've got round it for now by using the noise reduction in the NUX, but it's not ideal.

Still a bit weird and phasy, and the HX drives don't play nicely in the Twin model, but as the experiment and stepping stone towards a better solution, it's working.

I used it at band practice through my new Fender FR10 the other night and it sounded fantastic in the mix. I think I'm a modelling convert now.

borntohang

A lot of cheaper power supplies aren't actually grounded all the way from socket to device, which doesn't always help. Not going to solve your phase issue, but worth looking at a decent isolated power setup.

When are you hearing the phase issues? Is it when you have particular effects on, or just in general?

Dave_Vader

I'm starting to think I might be imagining the phase issues. They're definitely not enough of a problem for me to go and buy another gigrig setup. It'll do while I'm flogging stuff to save up for the Stomp XL. (Probably my 1985 Roland Cube 60 and the HXFX itself (eventually) in case anybody's interested.)

But yes, the difference from power supply to power supply is quite the surprise. I went down this wormhole before with my old massive pedalboard (ended up with gigrig, but it still hummed) and don't want to get into that again.

Currently running the two things with 2 proper line 6 power supplies, and it's not too bad at all.