I manage a public venue. I have a full PA system with control room Allen & Heath mixer desk upwind and power amp stack downwind, all working well. For more casual use (dance classes, presentations etc) where the control room is locked I have a simple 8 channel mixer desk with limited functionality bolted to the wall in the main hall which can be used with minimal training. If both mixer line outputs are simply joined by Y junctions in the cables then on to the same power amp controller input, and if only one mixer is used/powered up at a time, are there impedance issues from the "off' mixer output affecting the "on" mixer. If so, are there any 'automatic' (foolproof) switching systems available?
If nothing else, such an arrangement is just screaming and begging to make ground loops and the attendant hum.
It might make sense to just have other small speakers for the small gigs. A small mixer and a couple powered speakers even. Those get set up for the gig and then stored. The beauty of that is you can also use them elsewhere.
It might make sense to just have other small speakers for the small gigs. A small mixer and a couple powered speakers even. Those get set up for the gig and then stored. The beauty of that is you can also use them elsewhere.
Your 'Y Junction' method will probably work fine but is certain to be sub optimal because of possible back feeding/loading issues.
You properly need changeover switching in the signal chain probably at the amp rack and remotely controllable ie relay switching etc (Control switch at the 8ch desk position)
Alternately you could route the signals via a two input mixer stage and this will allow you to reduce gain for the 'punter' desk feed giving some system protection.
Dan.
You properly need changeover switching in the signal chain probably at the amp rack and remotely controllable ie relay switching etc (Control switch at the 8ch desk position)
Alternately you could route the signals via a two input mixer stage and this will allow you to reduce gain for the 'punter' desk feed giving some system protection.
Dan.
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Thank you Enzo and Dan, Ground loops, in particular, I can see would be a stopper. Both solutions offered make good sense. If I added a two Channel mixer would this be likely to downgrade the signal of the master desk?
Depends on the mixer.
I'd try and find a rackmount zone mixer which has a couple of inputs, outputs, and options to switch between inputs. Nice simple signal chain in there - no tone controls etc to mess anything up. It'll be expecting line level, too - most small desks are geared up for mic-level signals on the XLR inputs, so you'd easily clip the input stage if you were feeding from another desk.
Chris
I suggested a simple 2 input mixer for the ability to preset levels.
Sure to work and the simplest would be a balanced two input switcher, remotely controllable.
A rack mount box containing relays would be perfectly suitable and would serve as amp rack input selector.
The switching might need to be make before break to eliminate thumps/clicks when switching.
Dan.
Sure to work and the simplest would be a balanced two input switcher, remotely controllable.
A rack mount box containing relays would be perfectly suitable and would serve as amp rack input selector.
The switching might need to be make before break to eliminate thumps/clicks when switching.
Dan.
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