Due to a slight hum in the lead channel, I've descided to do some experimenting with pre amp tubes. I know there's a lot of writing done, but still, I want to share my experiences.
First of all, I'm the proud owner of a 1991 Mark IVa bubinga combo. In the past, I've changed the inner 6L6 power tubes with "winged =C=" tubes, and for the outher pair I've got EL34 shark tubes. The winged =C= tubes made a difference in more bottom and tighter sound.
Now, to the point. As stated, I had some humming in the lead channel. First of all I've changed V3 with a Fender 12AX7. Noise and hum were less, but gain was reduced.
Then, I've put an old Siemens 12AX7 in the V3 position. Noise and hum back to beginning, but a lot more tightness in the sound, so, that was a slight improvement for me.
Then I've changed the V1 Mesa pre-amp tube with an old Mullard 12AX7, made in britain, no reissue !
When I powerd up, and plugged on the strings of my Gibson LP, I was blown away !!! The Mark IV sounded like an amp on stereoids ! Volume was (by hearing) like doubled, no noise, allmost no hum.( I still can hear a slight hum with my ear next to the speaker, like the 50Hz of the fan motor, but really nothing to mention about.)
Instead of putting master volume on 3, I now put it just above 2.
On 3, I've got feedback, which before the change, I only had feedback with master volume above 4 (amp is on tweed power / Simul Class)
Sustain on allmost every note !
Now, I'm just afraid that the Mullard will not hold, because it's like it's pushed to the upper limits ( I don't know .... )
Sound is unbelievable, but is the Mullard strong enough for the Mesa circuitry ? Anyone has some experience ?
First of all, I'm the proud owner of a 1991 Mark IVa bubinga combo. In the past, I've changed the inner 6L6 power tubes with "winged =C=" tubes, and for the outher pair I've got EL34 shark tubes. The winged =C= tubes made a difference in more bottom and tighter sound.
Now, to the point. As stated, I had some humming in the lead channel. First of all I've changed V3 with a Fender 12AX7. Noise and hum were less, but gain was reduced.
Then, I've put an old Siemens 12AX7 in the V3 position. Noise and hum back to beginning, but a lot more tightness in the sound, so, that was a slight improvement for me.
Then I've changed the V1 Mesa pre-amp tube with an old Mullard 12AX7, made in britain, no reissue !
When I powerd up, and plugged on the strings of my Gibson LP, I was blown away !!! The Mark IV sounded like an amp on stereoids ! Volume was (by hearing) like doubled, no noise, allmost no hum.( I still can hear a slight hum with my ear next to the speaker, like the 50Hz of the fan motor, but really nothing to mention about.)
Instead of putting master volume on 3, I now put it just above 2.
On 3, I've got feedback, which before the change, I only had feedback with master volume above 4 (amp is on tweed power / Simul Class)
Sustain on allmost every note !
Now, I'm just afraid that the Mullard will not hold, because it's like it's pushed to the upper limits ( I don't know .... )
Sound is unbelievable, but is the Mullard strong enough for the Mesa circuitry ? Anyone has some experience ?
