Balanced outs hum

S

Sharkdog

Member
Well I finally played live w/ my AFX last night. Set up was balanced Out 1 L/R to PA (FOH & stage monitors) and Out 2 into SLA-2 > Avatar 2x12 w/ 2 V30's. I had the FX loop in the chain before the cab so the cab only affected the FOH and not the Avatar.

I got there early to set it up and see what kind of tweaking the global EQ's for 1 & 2 may need. We got it set up tweaked to taste and good to go, until...

Loud hum started (?) then it stopped. Then it happened again when we started playing. I had the ground lift on and then shut it off - helped eliminate some but not all. It was affecting the singers in ear situation so we quickly pulled Out 1 and miced the cab and I had to tweak the cab EQ on the fly - I only had it as support (thank god I did bring it!). I'll tell ya that once I got it dialed in a bit it was great - still more tweaking I could have done on the cab sound but I spent most of my tweaking time the last few weeks using our practice PA and my studio monitors to focus on the FOH.

I got set it up today and have been using an XLR > 1/4" into my Lexington Alpha > my Bm5a's but switched it to 1/4" > 1/4" into the unbalanced and it was much better - less noisy and also not as hot (very hot using the balanced outs).

I was disappointed not being able to use the PA but it worked out. It shouldn't be that big of a deal to run out of the unbalanced outs to PA should it?

All in all I'm loving this thing despite last night's debacle (which is my fault).
 
Was phantom power on with that channel on the board?

Moving to connections and routing as this is not Ultra specific.
 
Sharkdog said:
Loud hum started (?) then it stopped. Then it happened again when we started playing. I had the ground lift on and then shut it off - helped eliminate some but not all.
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What kind of board? Ground loop hum at the console input is always due to improper grounding in the console. It's a particularly common problem in lower-cost consoles.

I got set it up today and have been using an XLR > 1/4" into my Lexington Alpha > my Bm5a's but switched it to 1/4" > 1/4" into the unbalanced and it was much better - less noisy and also not as hot (very hot using the balanced outs).
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Balanced is always better, but it requires that the receiving device also have balanced inputs. Consumer type devices - including many computer sound interfaces - expect to see lower "line" levels than pro gear produces. If the signal is too hot, reduce the level in the receiving device and/or the Axe-Fx. This is how you maximize signal to noise.

It shouldn't be that big of a deal to run out of the unbalanced outs to PA should it?
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It will make any ground loop hum worse, not better.
 
This may be a dumb question, but what is the Ultra's ground lift on/off arrangement? The manual doesn't spell this out but from looking at the pic of the back panel in the manual, I'm gonna guess that ground lift is ON when the switch is moved in the direction of the arrow (i.e. looking from the back of the unit the switch is to the left)?
 
Chad said:
This may be a dumb question, but what is the Ultra's ground lift on/off arrangement? The manual doesn't spell this out but from looking at the pic of the back panel in the manual, I'm gonna guess that ground lift is ON when the switch is moved in the direction of the arrow (i.e. looking from the back of the unit the switch is to the left)?
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Anybody? I probably should have started a new thread to ask this, but I "used the search function" and was lead here. :)
 
It appears that the GND LIFT switch lifts the shield ground on the balanced outputs when the switch is moved in the direction of the arrow.
 
I've done about 40 shows with my standard (XLR out 1 to the board, output 2 to a Crown XLS600 to a couple of wedges). At two shows I had hum that couldn't be removed with the ground lift on the Axe. Both times we successfully removed the hum with a ground lift on one or both of our powered subs.

If this situation happens again, I would suggest trying to lift other things until you find the source of the hum.
 
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