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Ampeg RB 115 Huge Volume drop during a gig.

K

kickshoot

Nov 12, 2019
87
57
#1
I was at the very end of the last song during a gig last night and the volume on my Ampeg RB 115 dropped to a very low level. It was the last few seconds of the last song. The volume dropped sol low you couldn't really hear it with the band playing. When the band finished I could hear the bass but the volume was very low. Is this some kind of protection circuit for over heating or some built in compressor with no controls. I love the tone of the amp. Any help would be appreciated.
 
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#3
kickshoot said:
I was at the very end of the last song during a gig last night and the volume on my Ampeg RB 115 dropped to a very low level. It was the last few seconds of the last song. The volume dropped sol low you couldn't really hear it with the band playing. When the band finished I could hear the bass but the volume was very low. Is this some kind of protection circuit for over heating or some built in compressor with no controls. I love the tone of the amp. Any help would be appreciated.
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Take it to a qualified tech and see if the problem can be duplicated? In the meantime, you could check the "cords" you used and any other equipment in line to see if they may be the cause. Even your bass?? Batteries?
 
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#4
If it happened at the end of the gig, I'd guess thermal protection. And an authorized service center/tech is likely the next step.

I hate problems like this.... potentially intermittent, and hard to reproduce. Years ago, I had this type of problem with a Kustom Groove Bass 1200. The clipping was causing it to go into thermal protection mode & shut down, I'd have to power up/down in the middle of a song to get it back. It obviously didn't like the signal clipping. GOOD LUCK!!!! Keep us posted, in case others have similar issues.
 
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#5
I run an Ampeg PF-500, and although it hasn't happened to me (yet), they are well known for shutting down into thermnal protection mode when it's most inconvenient. However, it has a "Fault" LED that indicates when it does.

Both schematics show a limiter before the power amplifier, but I would imagine that's just a compressor that's activated when necessary. There's no indication in the literature if yours has thermal protection circuitry or not.
 
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#6
kickshoot said:
I was at the very end of the last song during a gig last night and the volume on my Ampeg RB 115 dropped to a very low level. It was the last few seconds of the last song. The volume dropped sol low you couldn't really hear it with the band playing. When the band finished I could hear the bass but the volume was very low. Is this some kind of protection circuit for over heating or some built in compressor with no controls. I love the tone of the amp. Any help would be appreciated.
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More details needed.

PA support or not?
Size of band?
How loud is the band?
Amp new or used?

Absent PA support, and in a reasonably loud band, good luck. The amp's rated at only 100 watts w/o an extension cab connected.
 
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#7
henryjurstin13 said:
If it happened at the end of the gig, I'd guess thermal protection. And an authorized service center/tech is likely the next step.

I hate problems like this.... potentially intermittent, and hard to reproduce. Years ago, I had this type of problem with a Kustom Groove Bass 1200. The clipping was causing it to go into thermal protection mode & shut down, I'd have to power up/down in the middle of a song to get it back. It obviously didn't like the signal clipping. GOOD LUCK!!!! Keep us posted, in case others have similar issues.
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That’s a wildly speculative guess without proper diagnostics.
 
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#11
eniac said:
More details needed.

PA support or not?
Size of band?
How loud is the band?
Amp new or used?

Absent PA support, and in a reasonably loud band, good luck. The amp's rated at only 100 watts w/o an extension cab connected.
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We were the backing band in a jam. We are 3 piece blues, blues/rock band. Amp was plugged in to PA through di. Not really loud. Heavier band did play on the equipment. May have been a little louder. Amp is used. Only used it a couple times before. Shorter gigs than this one. Other times it did fine.
 
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#13
kickshoot said:
We were the backing band in a jam. We are 3 piece blues, blues/rock band. Amp was plugged in to PA through di. Not really loud. Heavier band did play on the equipment. May have been a little louder. Amp is used. Only used it a couple times before. Shorter gigs than this one. Other times it did fine.
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You mentioned the amp bought used, suggest you remove the metal housing then clean/blow those electronic if dust found around.
 
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#14
Yahboy said:
You mentioned the amp bought used, suggest you remove the metal housing then clean/blow those electronic if dust found around.
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I suggest leaving it alone and not creating new problems. There may be nothing wrong with the amp.

If the problem returns, proper troubleshooting is the next step.
 
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