I'm currently in the process of switching tubes in and out, but am fairly certain what I'm dealing with is not tube-related on my nearly-5-year-old Mark V head.
Once the amp has been on anywhere from 15 minutes to an hour or two, if I stop playing on any channel for a while I can hear what sounds like a noisegate activating--the usual background noise (I keep the volume pot on my guitar up) completely disappears. When I start playing again, there's an ugly instant opening of the nonexistent gate and things sound noisier than usual for a few seconds, then back to normal till it happens again. When it happens on the clean channel, as soon as I "open the gate" by playing again output is low and noise is extremely high. This goes away completely only when I switch channels. I can go back to the clean channel after and it sounds fine.
What I know it isn't: Guitars, cab, rectifier tube, power tubes, interference, dirty power, cables, anything along the signal path between guitars and amp (because I've tested extensively with pedal/rack gear excluded).
What I'm almost certain it isn't: pre-amp tubes. I'll know for sure after a week or two of swapping.
Has anyone experienced this bad compressor/gate-like problem? I know it sounds ridiculous, but that's the best way I can describe it for anyone who has had the misfortune of using a cheap gate. In fact, when this first happened, I blamed a used compressor I bought thinking smoke damage had caused intermittent connections in the circuit. This doesn't sound tube-related at all. Because it's a global phenomenon I can't isolate it to any one channel, though the clean channel is the only one that requires switching to clear up. On the higher gain channels, playing a bit is enough to make it go away. Simply put, playing a moment with high gain just seems to clear up the output.
I'm worried that when I send the amp to Mesa (it's nearly out of warranty but I still have time) they won't find anything. Occasionally I go hours without any problems at all. If I knew what could possibly be causing it, I could describe it on the phone as such and possibly have a better chance of having the problem fixed the first time. I trust their tech services, but will be anxious all the same, especially with warranty approaching expiration.
Once the amp has been on anywhere from 15 minutes to an hour or two, if I stop playing on any channel for a while I can hear what sounds like a noisegate activating--the usual background noise (I keep the volume pot on my guitar up) completely disappears. When I start playing again, there's an ugly instant opening of the nonexistent gate and things sound noisier than usual for a few seconds, then back to normal till it happens again. When it happens on the clean channel, as soon as I "open the gate" by playing again output is low and noise is extremely high. This goes away completely only when I switch channels. I can go back to the clean channel after and it sounds fine.
What I know it isn't: Guitars, cab, rectifier tube, power tubes, interference, dirty power, cables, anything along the signal path between guitars and amp (because I've tested extensively with pedal/rack gear excluded).
What I'm almost certain it isn't: pre-amp tubes. I'll know for sure after a week or two of swapping.
Has anyone experienced this bad compressor/gate-like problem? I know it sounds ridiculous, but that's the best way I can describe it for anyone who has had the misfortune of using a cheap gate. In fact, when this first happened, I blamed a used compressor I bought thinking smoke damage had caused intermittent connections in the circuit. This doesn't sound tube-related at all. Because it's a global phenomenon I can't isolate it to any one channel, though the clean channel is the only one that requires switching to clear up. On the higher gain channels, playing a bit is enough to make it go away. Simply put, playing a moment with high gain just seems to clear up the output.
I'm worried that when I send the amp to Mesa (it's nearly out of warranty but I still have time) they won't find anything. Occasionally I go hours without any problems at all. If I knew what could possibly be causing it, I could describe it on the phone as such and possibly have a better chance of having the problem fixed the first time. I trust their tech services, but will be anxious all the same, especially with warranty approaching expiration.
