Hello guys, i have a marshall jmp1 preamp, both distortion channels have very little volume compared to the clean chanels, OD1 sounds very quiet, OD2 sounds a little louder than OD1, and both Clean Channels have normal volume, theres also strange pops, clicks and undisired distortion some times when hitting hitting low bassy note. Tubes have been replaced two times and a factory reset has been made in case that was the issue, but the problem remains. Anyone had the same problems? Any idea on how to fix it?
Jmp1 Volume Loss On Distortion Channels
- Thread starter angel84
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mickeydg5
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Have you tried checking or swapping V1 and V2 tubes?
Len
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Missed that. Maybe dirty tube sockets or cold solder joints at the tube sockets.
Yeah I've done all the tube thing already and it has not worked , but...you know, there are a lot of things that could go wrong, any suggestions on a good quality type/brand of tubes? maybe i could give it a shot again with a different brand, Ive tried with sovtek and ehx
mickeydg5
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Sorry I missed that too. If you have tried a couple of other tubes just make sure the pins sit tight in the sockets and that all is clean. Hit the pin tubes and sockets with a good electronics contact cleaner.
Make sure the power hitting the opamps is good. It could be a opamp as well. And as mentioned a solder pad/joint could be an issue.
Make sure the power hitting the opamps is good. It could be a opamp as well. And as mentioned a solder pad/joint could be an issue.
angel, what's your technical proficiency?
these things are pretty much all high proficiency tech work, but, there are a few things you might be able to do. Best bet, is to give it a real close look over & inspect everything. Look for obvious things that look broken or burnt.
I'm not very technically proficient, so, when I noticed that you have swapped tubes, I figured that it's probably above my paygrade.
What is your signal chain?
guitar >> JMP-1 >> mixer? or? effects?
Try & let us know as much as possible. There are a few things I do know about this unit, because I've owned mine since '92/3 +/-...
these things are pretty much all high proficiency tech work, but, there are a few things you might be able to do. Best bet, is to give it a real close look over & inspect everything. Look for obvious things that look broken or burnt.
I'm not very technically proficient, so, when I noticed that you have swapped tubes, I figured that it's probably above my paygrade.
What is your signal chain?
guitar >> JMP-1 >> mixer? or? effects?
Try & let us know as much as possible. There are a few things I do know about this unit, because I've owned mine since '92/3 +/-...
&...
to the forum...
to the forum...Thanks!!!!! well I'm not very technically proficient either, this is my second tube unit, I used to have a 5150, but it was wrecked by a friend (don't loan your amps!!), but other than that i don't really know much about the tube world, I'm planning on buying a different amp in the next few months, but I would still like to keep my JMP-1, I just love the sound. I bought it 3 years ago from a guy that maybe had not used it for years, it was in great condition, only had screw marks from being in a rack, but it was almost flawless, it even had the original tubes, that somehow managed to last almost two years and a half, which tells me that maybe it had not been played too much, then all of the sudden it started having all this problems and that was when I decided to change tubes. I both read and watched various tutorials on how to do it, but maybe I damaged something or did something wrong in the process, but everything seems to bee ok and in place. One thing that I have failed to mention is that, the tubes that I have tried are not as "bright" as the original ones were when I first bought it, you could see them through the vent very clearly and the ones that I have tried after are very dim, but i don't know if modern preamp tubes are supposed to be like that or if i just had bad look and purchased bad tubes.
Signal chain: Parker Nitefly >> JMP-1 >> Rocktron Velocity 100 >> Marshall 4x12
By the way, i have a POD X3 that I use for monitoring from time to time and i have used it with the Rocktron power amp and it sounds fine, so the problem is not in the power amp
Signal chain: Parker Nitefly >> JMP-1 >> Rocktron Velocity 100 >> Marshall 4x12
By the way, i have a POD X3 that I use for monitoring from time to time and i have used it with the Rocktron power amp and it sounds fine, so the problem is not in the power amp
Ok, I was wondering if you were using anything in the effects loop. The loop is sensitive & it's prone to act up, by making the unit distort & lose volume when overdriven.
I don't know what it could be. Try wiggling the distortion channel tube while playing. Tube will get hot, so use a pot holder, or similar to not get burned.
I don't know what it could be. Try wiggling the distortion channel tube while playing. Tube will get hot, so use a pot holder, or similar to not get burned.
Ricksta62
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Hello Angel84, did you end up finding out what the issue was? I am having a similar problem now. Lower volume and more a clipping like distorting, notice more on my OD1 than the OD2.
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