Hi,
I would like to ask your opinion, advice with regard a hum / creaky sound, which is noticeable only in Simulclass - pentode mode on my Mark IV amp. The guitar tones are audible too, but the hum is very strong as well.
It is not audible in the first seconds of playing, however after a minute, the noise appears, specially at ch2 and lead ch.
After a while, 30 minutes or so (I did not measured it) this hum goes away and the head works fine even in simulclass - pentode mode.
The same noise is at tweed or full power as well, but if I switch to triode or A class or any of these combination the noise disappears.
The head was purchased last week and this is my first Mesa, so I'm new hear guys. It was not used for the last 6 years according to the previous owner.
When I tried the amp before I bought it I did not discovered this fault. I did not hear it even when I was playing on it in our practice room first time this week.
It came out the second time, when I also noticed that one poweramp tube (the one on the right side) was lightning much weaker as the others.
After this I have replaced all poweramp tubes. The original 6l6 GC STR430 tubes were replaced for the same color code (green) 6l6 GC STR440 tubes.
Unfortunately the creaky sound still remained on our friday practice, so I switched to triode and continued playing.
Upon we played few song and head a brake I switched back to pentode mode and the hum disappeared! Thereafter I continued playing in the simulclass-pentode mode without any problems for the next 2 hrs.
The next day I switched on again and the hum came back unfortunately...
Thanks in advance for your comments
I would like to ask your opinion, advice with regard a hum / creaky sound, which is noticeable only in Simulclass - pentode mode on my Mark IV amp. The guitar tones are audible too, but the hum is very strong as well.
It is not audible in the first seconds of playing, however after a minute, the noise appears, specially at ch2 and lead ch.
After a while, 30 minutes or so (I did not measured it) this hum goes away and the head works fine even in simulclass - pentode mode.
The same noise is at tweed or full power as well, but if I switch to triode or A class or any of these combination the noise disappears.
The head was purchased last week and this is my first Mesa, so I'm new hear guys. It was not used for the last 6 years according to the previous owner.
When I tried the amp before I bought it I did not discovered this fault. I did not hear it even when I was playing on it in our practice room first time this week.
It came out the second time, when I also noticed that one poweramp tube (the one on the right side) was lightning much weaker as the others.
After this I have replaced all poweramp tubes. The original 6l6 GC STR430 tubes were replaced for the same color code (green) 6l6 GC STR440 tubes.
Unfortunately the creaky sound still remained on our friday practice, so I switched to triode and continued playing.
Upon we played few song and head a brake I switched back to pentode mode and the hum disappeared! Thereafter I continued playing in the simulclass-pentode mode without any problems for the next 2 hrs.
The next day I switched on again and the hum came back unfortunately...
Thanks in advance for your comments
