Weird Hum Issue

L

Lareaubot

Member
Hi Fractal fam - I have a hum issue that's been vexing me for a while. Check it out: . As you can tell, this is a total tone killer, and while it only happens on mid to high gain tones, it's definitely not just something that comes with the territory on gainy amps. This is extra gnarly.

Here's all the relevant info:
1) "It's EMI, dude." I thought the same thing, so I brought it to a recording studio that I've used 6 times before that for sure has no EMI in the sound stage, and still got the noise.
2) "Then it's probably the guitar. Check your guitar shielding." This happened out of nowhere a few months back on all my guitars. I've used it with a PRS Custom 24 (of which I've checked the shielding and soldering), a Kiesel, a Les Paul Studio, a Jericho, and a Parker Fly. They all get the same noise, and in different locations within the house and elsewhere.
3) "Use a power conditioner." I use a Furman power conditioner. I've swapped it out for 2 other Furman power conditioners, same noise.
4) "...but are you SURE it's not EMI? Because this sounds like an EMI/grounding issue. Does your guitar make more noise when you move it around in certain directions?" I agree, it most definitely sounds like EMI, and yes, the guitar(s) make(s) more noise when I move it around in certain directions. As a matter of fact, I live in an old house, and I was so sure that this was EMI that I just shrugged it off for a while before attempting to solve it. But the fact that it still makes the same noise when I bring it other places makes me think it's not an EMI issue. Or at least, not JUST an EMI issue. (I had an electrician look at the outlets and the electrical grounding, and he said everything looks up to date and solid. The previous owners did a great job updating everything. And plus, the sound happens in other environments too.)
5) "Get one of those Hum X plugs. They don't always work well, but it's worth a shot." Tried it. The noise; it lives. "Okay, how about a Hum Debugger?" I haven't tried that, but I've heard those are tone killers for mid to high gain tones. That also seems like a scotch tape solution and I'd rather get to the core issue. But hey, if you have success with the Hum Debugger on mid to high gain tones, let me know. I'm willing to try it at this point.
6) "Check your cables. Probably a bad cable." I thought the same thing. I use D'Addario American Stage cables, and I've swapped out all the cables in my rig. I also stripped the rig down so that it's just the Axe Fx III -> Matrix GT800FX -> Mesa cab; the noise lives. Then, to rule out the Matrix and the cabinet, I did the Axe Fx III -> EV powered PA speaker. Again, it lives.
7) "Set your Gate block to sidechain input 1." Did it. That gets rid of the noise when I don't play, but then I hit a note or chord and the noise comes right back and pukes up the tone.
8) "What does your preset look like? Are you blasting the gain?" This happens on every preset with mid to high gain. Even a patch as simple as Input ->
Cameron Atomica at stock settings -> cab block with Mesa 4x12 -> Output has the noise. The beast. The kraken.

I'm having a hard time believing it's the Axe Fx III unit, because it just doesn't sound like an amp issue to me, particularly a digital amp issue. Plus, I've had the Axe Fx III since 2018 or so and I've never had this issue until a few months ago. However, it's not the Matrix, the Mesa cabinet, the PA, the guitars, the location, the cables, the power conditioner, the gate block, the gain level, or the preset.

Any other ideas?

edit I also swapped out the power cables on both the Axe Fx III and the Matrix. The noise. It lives.
 
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It sounds like a ground loop. The guitar's sound partially blocks it until the level decays to a certain point when the hum has a louder volume.

The issue usually happens when two AC-powered units are connected together via a 1/4" TS cable but one has a worse connection to the electrical ground than the other. The one with the problem sends voltage across the cable to the other, amplified at 50-60 Hz, which is a low-pitched hum.

Humbuster talks about a good solution.

Describe your system and what it's connected to and we can make better recommendations.
 
Thanks Greg, that's great info. I'll get a Humbuster today to see if that fixes anything.

My system is:

Axe Fx III Out1 -> XLR -> EV ZLX12 PA speaker
Axe Fx III Out3 -> TS -> Matrix GT800FX -> speaker cable -> Mesa 2x12

Axe and Matrix are plugged into a Furman floor unit power conditioner.
 
You are exactly showing what I have pointed for months.
Until Cliff turns red.
The best way I have found to minimize this is to Cooper tape the guitar. When the guitar is well shielded, you can live with it. You will hear it but not a lot.
Sadly, the noise is still non filtered while playing, even after the lovely effort Cliff has put it in in the recent noise gate update.

I also have humbusters and it does nothing. It came from the guitar and the gain
 
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@Greg Ferguson Okay, I bought a Humbuster cable and I'm still getting the noise. I have a friend coming over tomorrow with his Axe Fx III and I'm going to A/B them to see if it's just my unit. I also tried a Lehle P-ISO unit in various locations in the signal chain and at best it made no difference and at worst it made the noise way louder.

If anyone has any other ideas, please let me know! This is killing me.
 
@Brian Atkinson Guitar (I've used multiple different ones to make sure it's not a guitar issue) -> TS cable (similarly, I've used multiple different ones to make sure it's not a cable issue) -> Axe Fx III front input

Axe Fx III Out1 -> XLR (have also swapped multiple XLRs) -> EV ZLX12 PA speaker
Axe Fx III Out3 -> TS (have also swapped multiple TS cables and tried a Humbuster today) -> Matrix GT800FX -> speaker cable (again, tried multiple) -> Mesa 2x12.

The noise happens through the PA speaker and the Mesa cab.

The Axe and the Matrix are both plugged into an Atlas power conditioner. I've swapped the power conditioner out for 3 different Furman units just to make sure that's not the issue.

Most of the other troubleshooting I've done is listed in my original post. In addition to the Humbuster today, I also tried guitar -> TS -> Lehle DI box -> TS -> Axe front input, which is supposed to cancel ground loop noise, but it didn't do anything.

edit I've also tried different power supply cables for both the Axe and the Matrix, just to rule that out.
 
If you disconnect your output from EV, do you still get hum through the Mesa cab?

How about the other way (disconnect your output to the matrix)? Do you still get hum through the EV?

Is there anything else plugged into the EV?

Are you plugged into a computer via USB? I've never had a gl problem with this on my AxeFX3, but I have with other digital audio devices.

Man I hate debugging ground loops. I feel your pain and frustration.
 
Just went back and listened to your recording. Probably not a ground loop. Since you hear it out of both sound reinforcement paths, the noise is most likely what you have already heard from others in this tread, EMI at the input.

Have you opened up the AxeFX3 and checked that all ribbon cables are properly seated?
 
the noise you have is exactly what I said 100 times in the forum … I told you the humbuster won’t do nothing 🤷 . Do you have it when you play with headphones ? If yes … read back what I’ve said. If not, you will have a chance.
 
I appreciate all the input!

In disconnecting the Mesa there's still a hum through the EV, as well as vice versa.

Nothing else is plugged into the EV.

I'm currently not plugged into the USB.

I haven't opened up the Axe because I'm not comfortable enough in that area to know what I'm doing. I wish I was competent with that stuff but it's just not my forte.

@My name is mud I feel you. Have you talked to Fractal customer service about sending the unit in to get it fixed? My friend is bringing his III unit over tomorrow and I'll be able to tell for sure if it's my Axe or if it's something else. If it's my Axe, I'll reach out to the customer service and see what can be done. I'm pretty sure I'm outside the warranty period but hopefully they can do something.
 
Brian Atkinson said:
Just went back and listened to your recording. Probably not a ground loop. Since you hear it out of both sound reinforcement paths, the noise is most likely what you have already heard from others in this tread, EMI at the input.

Have you opened up the AxeFX3 and checked that all ribbon cables are properly seated?
Click to expand...
Oh no don’t tell him to open the unit 🤣
That’s not the unit.

@Lareaubot

The 2 culprits are the noise gate, and the pickups / guitar shielding.
If you have a gate that don’t filter the noise as soon as you do a note, the only way is to have super shielded guitars. As I didn’t wanted to buy myself a gate once again, I have shielded my guitars and now it is ok. Not perfect but way better.
That’s not a problem from the unit, they won’t do nothing for that.
 
turn all gates off, disconnect everything except power and headphones, turn off computer = silent
connect a guitar cable and guitar, don't touch strings or any metal part of guitar = noise
touch strings = noise should be reduced
roll down guitar volume knob = silent

If these are correct this is for sure EMI/RFI and can be reduced by shielding your guitars' cavities or a dummy coil. If the noise gets worse when touching a metal part of the guitar, that component is not grounded properly inside your guitar. If the noise is particularly bad on one guitar (after accounting for the increased noise of single coils), it's possible that guitar has a ground loop in its wiring, like if the 4 pots in an LP are all grounded to each other and the output. Everything should only have one path to ground.

From there just add one thing to your rig at a time i.e. power amp/cab, computer, PA, etc.
 
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Alright everyone, thanks for all your input. Here's a big ole hairy update:

I shielded the guitar and the noise still lived. This wasn't a surprise because as I've said, this has been happening with all my guitars as well as other people's. These are all well made guitars, so I wasn't convinced that extra shielding would do anything. It did not.

Critically, my friend brought his Axe III over with a bunch of different guitars and cables, and his equipment made the noise too. His stuff most definitely does NOT make a hum at his place, so that was great info because it told me it's not my equipment, it's my house. (I'm not sure what was happening when I brought my rig other places and still got the hum. That's to be determined at this point.)

On other forums, people suggested a plethora of different DI boxes, power conditioners, wireless systems, and noise gates. I had already tried a Hum X plug and that did nothing, and I'm already using a Furman power conditioner which did nothing. I didn't think noise gates were the answer because the noise ruins the tone while I'm playing, which a noise gate wouldn't fix.

I bought a Lehle P-ISO DI box and tried it in every possible location, and at best it did nothing and at worst it made the noise twice a loud. Returned. I tried a Pyle Pro Compact Mini Hum Eliminator, which actually lessened the noise quite a bit but also skunked the tone completely. (Again, the preset I was using to judge the tone had a Cameron Atomica at stock, so we're not talking super high gain here.) I needed to create a completely different preset and redo all the blocks to get the tone back to normal, which unfortunately brought the noise back up to about 95% of what it was with the box disconnected, so a no-go but at least there was progress.

I tried a Joyo wireless system which did nothing to reduce the noise, but I kinda dug the system so I'm hanging onto that one. I tried a Tripp Lite LC1200 Line Conditioner which did nothing. I tried a Behringer Ultra-DI which didn't make anything worse like the Lehle box did, but it didn't improve anything either. I took everything out of the rack to make sure it wasn't an issue with rack noise, and that did nothing. I even covered any areas of the basement that seemed to make the hum worse with copper tape and aluminum foil out of desperation. Nothing.

Today I tried an Electro Harmonix Hum Debugger and...much less noise! There's still a bit more than there should be, but it's significantly better. Despite what EH promises, it definitely changes the tone a bit. Less low end and more high end, at least from the 5 minutes I've spent with it today. There's no difference between the low and high setting regarding how much hum it eliminates, but this is the closest I've gotten to a solution. This is at least livable.

If anyone else has any other suggestions that might work better, I'm still all ears, but this is probably the end of my hum-killing adventure for the time being.
 
Thanks for typing all that up, very interesting. Every guitarist has these issues at some point and they really make it tough to have a good time. Maybe a power conditioner could help? Seems like you have the problem isolated to the house at this point.
 
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