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Author Topic: 2 QSC Amps Show Same Symptoms?  (Read 2299 times)

Dan Forrest

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2 QSC Amps Show Same Symptoms?
« on: March 02, 2017, 08:23:57 pm »

Hi! I have a big gig tomorrow night (benefit show, sold out, yadda yadda) and went out and purchased a used QSC RMX 850 power amp. When I got it home, it was popping like crazy, as if it was clipping but it wasn't. I cleaned the inside and deoxed the pots to no avail. I returned the unit and swapped it for another identical used RMX 850, only to find it has the SAME PROBLEM! I've ruled out the mixer/cable/mics, as I can substitute my PV-1500 amp and my Behringer mixer amp with no issues whatsover. Is there a dip switch setting on this model that I might need to change, or is there some special consideration I should be taking when using this seemingly simple amp? Thanks in advance for your help!
« Last Edit: March 04, 2017, 05:15:16 am by Craig Leerman »
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Mac Kerr

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Re: 2 QSC Amps Show Same Symptoms?
« Reply #1 on: March 02, 2017, 11:03:10 pm »

Hi! I have a big gig tomorrow night

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Dennis Wiggins

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Re: 2 QSC Amps Show Same Symptoms?
« Reply #2 on: March 04, 2017, 08:33:56 am »

Google this: 

QSC RMX 850

Get this:

https://www.qsc.com/resource-files/productresources/amp/discontinued/rmx/q_amp_rmx_series2ru_usermanual.pdf

--------See Page 7----------

Begin with this setup for simple stereo.

Starting at the top DIP switch:
On
On
On
Off
Off
Off
Off
On
On
On

This sets:
High-pass  30hz
Stereo (Not paralled input)
Not bridged

<disclaimer>  This info is from the QSC manual; I do not own any version of this amp.

-Dennis
« Last Edit: March 04, 2017, 08:47:00 am by Dennis Wiggins »
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Bob Lee

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Re: 2 QSC Amps Show Same Symptoms?
« Reply #3 on: March 21, 2017, 06:39:57 pm »

Hi! I have a big gig tomorrow night (benefit show, sold out, yadda yadda) and went out and purchased a used QSC RMX 850 power amp. When I got it home, it was popping like crazy, as if it was clipping but it wasn't. I cleaned the inside and deoxed the pots to no avail. I returned the unit and swapped it for another identical used RMX 850, only to find it has the SAME PROBLEM! I've ruled out the mixer/cable/mics, as I can substitute my PV-1500 amp and my Behringer mixer amp with no issues whatsover. Is there a dip switch setting on this model that I might need to change, or is there some special consideration I should be taking when using this seemingly simple amp? Thanks in advance for your help!

Make sure the amps aren't in bridged mono. Or if you do run them bridged, make sure the clip limiter and LF filter on channel 2 are switched off. What you describe sounds like what happens if the amp is bridged but with channel 2's LF filter engaged.
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Bob Lee
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Bob Faulkner

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Re: 2 QSC Amps Show Same Symptoms?
« Reply #4 on: March 21, 2017, 06:48:10 pm »

Make sure the amps aren't in bridged mono. Or if you do run them bridged, make sure the clip limiter and LF filter on channel 2 are switched off. What you describe sounds like what happens if the amp is bridged but with channel 2's LF filter engaged.
Hey Bob - what you stated here... does that hold true with the PLX line?  I think I have the limiter/filter set on my PLX for channel 2, but I've never noticed any issues with it (as what the poster presented). 

Thanks.
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lindsay Dean

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Re: 2 QSC Amps Show Same Symptoms?
« Reply #5 on: March 22, 2017, 03:36:41 pm »

Had some of the same amps, same symptoms.
 cleaned pots, no difference.
 replaced the pots, all went back to normal.
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Re: 2 QSC Amps Show Same Symptoms?
¬ę Reply #5 on: March 22, 2017, 03:36:41 pm ¬Ľ


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