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70 volt system - what am I doing wrong?

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Mike Caldwell:
What outputs are you connected to on the amp?
Do you have it switched to 70 volt mode, high?
What is the input source?
How loud are you trying to run it at?
Are you trying to make the system thump by boosting a lot of low end?

Brad Worrell:
The connections were all done properly and I was running some pop music thru at moderate volume, both via a directly attached iPhone and also from RCA "record" outputs on a mixer. While it's a long run for 8ohm, I also tried that, wiring speakers parallel/series to get 8ohms, bypassing transformers, etc. Same result.

The "Divide and Conquer" is obviously going to be the way to go. I've performed most of that but the one thing I haven't done is connected all speaker to amp separate of the installed wiring grid.

Thanks for all the prompt and helpful replies. I've got my work cut out for me...  :-\

Mike Caldwell:
With the system properly connected and the speaker tap settings set for 70 volt operation
when it's turned up is the ring around the amp level control flashing red?


Brad Worrell:

--- Quote from: Mike Caldwell on June 27, 2021, 06:45:43 PM ---With the system properly connected and the speaker tap settings set for 70 volt operation
when it's turned up do you the ring around the amp levels control flashing red?

--- End quote ---

Nope. At no point was I clipping the input.

Brad Worrell:

--- Quote from: Milt Hathaway on June 27, 2021, 02:27:42 AM ---You may have a feedback issue. Not the usual acoustic feedback, but feedback induced from the 70v cables into any mic level cables going into the system. Typically this feedback is at frequencies too high to be heard, but still low enough to find it's way through the mic preamps. It will heat an amp up to shutdown levels pretty quickly. See how long the amp stays on with nothing hooked to the inputs. If it stays on, you've found your problem and will need to re-route some cabling.

--- End quote ---

I think you called it. The amp wasn't showing any changes in signal lighting when shutting off. It just went silent, so I couldn't try your suggestion, BUT, after trouble shooting everything else, with the feedback thing in mind, I freed up a balanced output from the mixer and used that (to the balanced inputs of the amp) and VOILA! everything works fine.


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