Axe-Fx Out to PA XLR: serious noise issues

bfinn19

bfinn19

Member
Am using an Axe-Fx II XL+. At home in the studio, output 1 balanced goes to a small mixer, then a digital power amp to studio monitors, and is dead quiet.

In church, the balanced out from Out 1 goes to the direct in (XLR) of the PA system (new high-end system, sound guys still getting the bugs out), and there is a horrendous high frequency hiss through the monitors & PA, which has been driving me (and the sound guy) crazy trying to resolve. It's definitely coming from my gear, and stops when I disconnect from the PA

The hum is present whether there is input (bass, front instrument in) or not, instrument jack in or no. Present with different XLR cables. It is not dependent on the output 1 volume. The ground lift reduces it but does not eliminate it. Power to the Fx is filtered with a Furman conditioner; bypassing the Furman makes no difference.

The sound guy usually gets frustrated quickly and demands I go thru a DI box, which is quiet, but obviously defeats the purpose of having the Axe live, losing all my nice effects, amp sims, etc

Any thoughts on what's going on here, and how to figure out/resolve it?

Thx
 
Have you tried different XLR cables? And also plugging into a different channel on the desk? I'm wondering if they might 'accidentally' have enabled some heavy compression on your channel or something unusual.

Also, not sure I understand why you would loose all your amps, effects etc if you go through a DI box? Do you mean cutting the Axe-Fx out of the equation and going back to your old gear?
 
He means that he plays his bass through a DI box, not through AFX.

Sounds like a ground loop. What else is in your rack, bfinn? Have you tried connecting your AFX via a DI box?
 
I would try to ground lift the XLR, after that the axe power cable and double check the soundguy do not have Phantom power (48v) on your inputs.
so far i would put my money on the power lift
 
Only the AFX and the Furman in the rack. Though about trying AFX unbalanced out to DI box (haven't tried it yet) but then that means digital->analog->digital. Also wouldn't the Fx out be too hot for a DI box?
 
Take the Axe-Fx out of the rack and connect it the PA.
This will tell you if the ground loop originates from the rack.
 
Tried different cables, different channels. Alternative I'm forced to do is bass->DI box, rather than bass->AFX->XLR out->PA
 
bfinn19 said:
Tried different cables, different channels. Alternative I'm forced to do is bass->DI box, rather than bass->AFX->XLR out->PA
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Plug the Axe FX into another outlet on the other side of the room, preferably in the same outlet/strip the board uses. Do you still hear the noise? If not then there is (for what ever reason) noise on that power outlet you 1st used. try different outlets in the room if possible is the meaning. If the noise is still there, do as was suggested and just plug the Axe in by itself. Any changes? It kinda sounds like a ground loop as mentioned, but it also could be that the "new" board inputs are still switched/set to mic-in only and not "line-in" perhaps, so the signal from the Axe coming in is too hot? Is there a -20 db pad on the channel inputs of this new board, and does that help when switched on? Since you are dead quiet at home I highly doubt the Axe is the issue or it would be noisy there too. Hope this helps... Oh yea, and fire the sound guy for having no patience....;)
 
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I've had similar issues with the XLR outs on mine in live situations. Sound guys getting horrible hiss from it, and my own monitors (Matrix power amp loaded Xitones) get horrible hiss from the XLR outs. However, if I use the 1/4" outs on the AxeFX into the same setups, no noise whatsoever.
 
bfinn19 said:
Only the AFX and the Furman in the rack. Though about trying AFX unbalanced out to DI box (haven't tried it yet) but then that means digital->analog->digital. Also wouldn't the Fx out be too hot for a DI box?
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This does not make sense: If you're going XLR out to PA, you're already Digital>Analog>Digital, unless you are plugging the AES output into the board, at which point, yes, you're going to get some horrible noise!
Try the DI method. And no, the Axe output is not too hot for a DI box. That's what it's for - reducing instrument/line level signal to mic level and matching impedance accordingly.
Set your Out 1 output to approximately 15-25% (should be plenty) so that the DI does not overload, in case it's a cheap one.
 
Since your "sound guys" already have a DI box, it's the easiest thing to do in your case to check what's going on. A DI should handle your AFX, especially if its a passive one. If that console is handling it directly, a DI certainly should. Plus you don't have to max your output level.
 
Ground loops normally manifest themselves as a hum or a buzz rather than a hiss.

Hiss is wideband noise (or white noise or even pink noise) that is not limited to an specific frequency. Ground loops are usually either the fundamental frequency of your mains power supply cycle or harmonics thereof.

One way of isolating the problem would also to be ask if the level of hiss changes with the amount of volume you have set on your Axe FX? Or is it a constant noise floor completely independent of volume?

Also does the amount of hiss (i.e. hiss volume) change when you are playing through the Axe FX? Does it subside when you play which may indicate some auto-levelling/compression being applied to raise the signal (and hence the noise) when no audio input is detected?
 
The OP calls this noise both "hum" and "hiss", so I wouldn't make a diagnosis based on word usage alone. :)

I've had ground loop problems sounding like high pitched squeals, whines, whatever. Had some trouble explaining what they sounded like.
 
Just one more thought - plug some headphones into the Axe and see if you hear the same hiss/hum/noise/etc.

If so, then the issue isn't connecting to the board, it's something between the bass and the Axe. If you've got single-coil pickups in your bass, it's entirely possibly the noise could be originating with the bass.
 
Get a Radial JDI Duplex. You can go into the line level XLR inputs off of the AXE-FX II and set the JDI to lift the ground. That should break the loop, and it delivers microphone level to the board. I use one to go into the theater board. It solved the horrible ground loop issues I was having which was because the pit was on a different circuit from the board. The also helped to lower the interference noise by breaking the line lengths up.
 
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vangrieg said:
The OP calls this noise both "hum" and "hiss", so I wouldn't make a diagnosis based on word usage alone. :)
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Yup... you're probably right there which reminds me of an old thread on the forum which tried to get some common ground about how to describe 'noise'. I guess if we get more of an apt/accurate description then we might have a chance of suggesting solutions... of course it could be both hiss AND hum!
 
Is there any other gear having ANY other issues with the church's new set up?
Is it just that one sound guy you have worked with, or can you try to work with someone else / fresh set of ears, eyes & attitude??
 
scottp said:
Is there any other gear having ANY other issues with the church's new set up?
Is it just that one sound guy you have worked with, or can you try to work with someone else / fresh set of ears, eyes & attitude??
Click to expand...

Especially the latter. :)
 
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