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Revisit JBL PRX615M scratchy until warmed up
Jim Layton:
We discussed trouble-shooting a while back. Thought I had it sorted out but no.
I have four PRX 615Ms. One of them (labeled to make sure it is the same one every time), will often randomly emit a quiet "scratchy" sound...like radio interference. It will do this with no XLR connection, just power, at several venues. The speaker is set for "monitor", which I think means there is an automatic gate. I tried that setting while using it as a mains speaker for a speech. I could hear the audio get cut off as the voice trailed off. Switched to mains and it went away.
Once the monitor has been on a while it seems to go away. When the event gets going I don't have time to go up and listen. I listen from FOH through headphones and don't hear anything.
The noise is pretty "gentle" and not harsh. I "think" the noise level is completely independent of the gain level on the amp but I am not sure. I'll have to try it next time.
I can pull the amp off and take a look. Any ideas?
Will Knight:
--- Quote from: Jim Layton on February 27, 2017, 08:48:20 AM ---We discussed trouble-shooting a while back. Thought I had it sorted out but no.
I have four PRX 615Ms. One of them (labeled to make sure it is the same one every time), will often randomly emit a quiet "scratchy" sound...like radio interference. It will do this with no XLR connection, just power, at several venues. The speaker is set for "monitor", which I think means there is an automatic gate. I tried that setting while using it as a mains speaker for a speech. I could hear the audio get cut off as the voice trailed off. Switched to mains and it went away.
Once the monitor has been on a while it seems to go away. When the event gets going I don't have time to go up and listen. I listen from FOH through headphones and don't hear anything.
The noise is pretty "gentle" and not harsh. I "think" the noise level is completely independent of the gain level on the amp but I am not sure. I'll have to try it next time.
I can pull the amp off and take a look. Any ideas?
--- End quote ---
With the amp off, check the wiring between the amp and the speakers. Sometimes depending on extended usage, the speaker connection may loosen just a tad due to the frequent cycles of heating and cooling. Would also check the actual Monitor switch for any deterioration/oxidation due to temp changes over time. Does the scratching also occur when / if you turn the gain knob up or down? If so, consider a VERY light spray of DeOxit. I have 612's where one exhibited a similar behavior and a bit of cleaning (air+DeOxit) did the trick.
Jim Layton:
--- Quote from: Will Knight on February 27, 2017, 09:01:12 AM ---With the amp off, check the wiring between the amp and the speakers. Sometimes depending on extended usage, the speaker connection may loosen just a tad due to the frequent cycles of heating and cooling. Would also check the actual Monitor switch for any deterioration/oxidation due to temp changes over time. Does the scratching also occur when / if you turn the gain knob up or down? If so, consider a VERY light spray of DeOxit. I have 612's where one exhibited a similar behavior and a bit of cleaning (air+DeOxit) did the trick.
--- End quote ---
I will do this. Thanks!
Bob Kidd:
--- Quote from: Jim Layton on February 27, 2017, 08:48:20 AM ---We discussed trouble-shooting a while back. Thought I had it sorted out but no.
I have four PRX 615Ms. One of them (labeled to make sure it is the same one every time), will often randomly emit a quiet "scratchy" sound...like radio interference. It will do this with no XLR connection, just power, at several venues. The speaker is set for "monitor", which I think means there is an automatic gate. I tried that setting while using it as a mains speaker for a speech. I could hear the audio get cut off as the voice trailed off. Switched to mains and it went away.
Once the monitor has been on a while it seems to go away. When the event gets going I don't have time to go up and listen. I listen from FOH through headphones and don't hear anything.
The noise is pretty "gentle" and not harsh. I "think" the noise level is completely independent of the gain level on the amp but I am not sure. I'll have to try it next time.
I can pull the amp off and take a look. Any ideas?
--- End quote ---
Definitely sounds like a dirty pot. I have had it occur on some of my speakers. Good cleaning should resolve it.
Matt Shep:
--- Quote from: Jim Layton on February 27, 2017, 08:48:20 AM ---We discussed trouble-shooting a while back. Thought I had it sorted out but no.
I have four PRX 615Ms. One of them (labeled to make sure it is the same one every time), will often randomly emit a quiet "scratchy" sound...like radio interference. It will do this with no XLR connection, just power, at several venues. The speaker is set for "monitor", which I think means there is an automatic gate. I tried that setting while using it as a mains speaker for a speech. I could hear the audio get cut off as the voice trailed off. Switched to mains and it went away.
Once the monitor has been on a while it seems to go away. When the event gets going I don't have time to go up and listen. I listen from FOH through headphones and don't hear anything.
The noise is pretty "gentle" and not harsh. I "think" the noise level is completely independent of the gain level on the amp but I am not sure. I'll have to try it next time.
I can pull the amp off and take a look. Any ideas?
--- End quote ---
sorry to bring up this topic from the start of the year but did you ever get this figured out.. one of my 615m's has the exact same problem as yours, gain doesn't affect it and once it has been on for a few of minutes and warmed up the noise goes away.
if not has anyone else have any solutions?
TIA
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