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Amp signal sent to both sides of a parallel input? Yikes.
Old 13th October 2013
  #1
Gear Head
 
NS3474's Avatar
 

Amp signal sent to both sides of a parallel input? Yikes.

Hey guys/gals,

So here's a little conundrum I'm hoping some of you electricity-minded folks can clear up for me. (Setup follows, and question is below in bold.)

I get a frantic call from a local rock club asking me to come in and "fix everything in the PA." When I get there the next morning, I find a QSC RMX5050 driving one Yamaha S115V box per side. (Yup, 1,000W/side hitting a 500W speaker.)

The house guy tells me amplifier powers on for a hot second before it snap/crackle/pops/dies. Faint smell of smoke.

So here was the problem . . . Amp channel 1 was being sent via NL4 to left speaker, amp channel 2 sent to right speaker . . . but as an added bonus, someone had daisy-chained the left and right boxes together with a 1/4". (At least they had the presence of mind to use speaker cable instead of a guitar plug?)

My grasp of this is that basically both amp channels were pushing against each other in this dysfunctional little audio family, but could someone clarify for me exactly what is going on as far as loads, resistance, etc.?

Thanks in advance.
Old 14th October 2013
  #2
Gear Maniac
To be sure I understand this right.

Both amp channels were going to their respective speakers, and then there was a jumper chaining the left and right together through parallel inputs/outputs. Basically connecting both amp channels with one cable?

Is that what you are describing?
Old 14th October 2013
  #3
Gear Head
 
NS3474's Avatar
 

Quote:
Originally Posted by cc14basketball View Post
To be sure I understand this right.

Both amp channels were going to their respective speakers, and then there was a jumper chaining the left and right together through parallel inputs/outputs. Basically connecting both amp channels with one cable?

Is that what you are describing?
Exactly right.
Old 14th October 2013
  #4
Gear Head
 
NS3474's Avatar
 

Quote:
Originally Posted by NS3474 View Post
Exactly right.
Just to clarify, it was the two speaker boxes (left/right) that were chained, not the amp channels themselves . . . but as I understand it, the end result is the same?
Old 14th October 2013
  #5
KEL
Lives for gear
 

generally, a smoke alarm is something to be avoided in:
live sound
Cooking
dentistry
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