JCM2000 DSL100 volume swell problem
Hi, I have a Marshall JCM2000 DSL100 along with a Marshall 1960A 4x12 cabinet.
I bought both units 2nd hand (came together), and it's in mint conditions. When I bought it, it looked brand new except for a few marks on the cabinet.
Not long after I bought it, I noticed that an weird sound would be coming out of the speakers (regardless if I was plugged in or not) - an airy sea shell kinda sound, with a smooth light crackly sound aswell...
When I was plugged in and playing, I also noticed that the volume would swell. Sometimes it would get louder, and then sometimes it would go softer.
I didn't do anything about it until it become REALLY noticable, and the swelling was unbearable..
I talked to an amp specialist and he recommended I get the amp reconditioned. So I got all valves replaced, balanced etc.. this solved the problem...
The amp has had very little use since, until recently.. It has been about 6 months since the valves were replaced and just the other day I noticed that the swelling has come back.
there is not sea shell sound (which is different from last time), but there is definately volume swell happening... and it is especially noticable at loud volumes..
it does not matter which guitar I use (I have 4).. the swelling is there...
is this a commen problem?
has anyone experienvced this problem before?
would replacing the vavles fix this problem? (I hope this is not necessary, as they are only 6 months old - with very little use)
could it be a balancing issue?
what else could cause this problem?
if I don't fix the problem, will it get worse?
I first noticed the volume swelling after I picked up my amp from my friends house, which is where I was storing my amp over the past 4 months...
I would use it about 2-3 times a week.... and I never noticed any problems at all..
It was only until I took it back to my house where I noticed a problem (volume swelling)
The swell might take 1 minute.. normally playing softer for the most part of its cycle... so in other words, it gets loud for about 5 - 10 seconds and then goes soft again...
I noticed when I was transporting my head/cabinet, that when I went over bumps, I would hear a metal rattling sound coming from the head..
I was wondering if the rattling set something out of balance.. because I remember my amp specialist telling me that he carefully balanced the valves...
I don't know the effect of unbalanced valves.. or why valves need to be balanced..
I am not familiar with the technical sides of valve amplifiers.. but I love them because they are so powerful and awesome sounding..
Perhaps when I transported it, I bumped the bias out?
what normally causes this problem I am having?