Monitor Interfearence

[pattonaudio]

Along with what Brian suggested, there may be a cross-connection on a neutral, quite a common feature on bad wiring (even by "professional" electricians) such that the route out and back tothe loads is not the same. Thus you get an inductive effect, which could be what the amps are picking up on.

 

If you were in NZ I'd be down there with my test equipment, as that is indeed an interesting "feature"...

 

 

I seen this happen in a few venues I have worked in even the grand opera house in belfast, may I suggest take a look to see where the amps are in location to the dimmers and also the induction loop system is there is one in place. chances are I could be as simple as balanceing cables and or moving the amps to another location.

[fireman]

slightly off topic but

 

I recently worked for u2 on the 360 tour, dallas schoo (edge's guitar tech) had a hum on the guitar rig, where would you start with that lot?

 

turned out to be a fan (spin around type not jump up and down type) touching the stage.

 

just goes to show it can be almost any thing and happen to anyone.

[paulears]

That's actually quite handy advice - because a few years ago there was a fire, and I remember seeing a whole pile of melted wiring that had been pulled out of a duct, and replaced. With a whole bunch of neutrals it would be quite simple to get some swapped, and not notice?

[obaka-san]

was there a live band? not unusual for guitars, basses, elec' violins, etc to pick up dimmer noise

[dbuckley]

I recently worked for u2 on the 360 tour, dallas schoo (edge's guitar tech) had a hum on the guitar rig, where would you start with that lot?

Guitar systems are the worst things to get noise out of because:

• The signal can be contaminated at source (think: single coil pickups)
  
• Low signal level
  
• Unbalanced connections
  
• The gain required for overdrive, whether box or amp based
  
• The absolute crappiness of most effects boxes
  
• The need for 'tone'...
  

The trick with a professional guitar rig is solid engineering to work around these features, and its no surprise a number of small, expensive, specialist suppliers make things like loop switchers to address the needs of this section of the professional guitarist.

 

Decades ago I humped for a Steve Hillage gig at Liverpool University and Hillage's tech had a heck of a time stopping the police radios from the next door but one police station from breaking through the guitar rig, eventually solved by a few rolls of baking foil screening the back of the racks...

 

If there any of the TurboSound guys still about from that gig; thanks for putting up with a million questions from some spotty faced youth; I gained a lot of useful knowledge that day.