Kiwifpms158
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- Oct 4, 2014
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Hi,
I've made the acquisition of a Mesa Boogie Studio Preamp and a Mesa Boogie 50/50.
Channel A of 50/50 delivers no sound below 5. The sound remains very low and linear between 5 and 10.
So I've decided to open the amp in order to check the tubes. I've noticed 2 strange things :
- The 4 power tubes are Groove Tubes GT-EL34B. I've read everything that it is recommended use Mesa tubes because of bias.
- The amps has been modified (see pictures). A pot has been wired to the 47uF capacitor.
Does anyone have an idea on the purpose of that pot ? Is it a bias setting ? How can I solve channel A issue ?
Thanks !
I've made the acquisition of a Mesa Boogie Studio Preamp and a Mesa Boogie 50/50.
Channel A of 50/50 delivers no sound below 5. The sound remains very low and linear between 5 and 10.
So I've decided to open the amp in order to check the tubes. I've noticed 2 strange things :
- The 4 power tubes are Groove Tubes GT-EL34B. I've read everything that it is recommended use Mesa tubes because of bias.
- The amps has been modified (see pictures). A pot has been wired to the 47uF capacitor.
Does anyone have an idea on the purpose of that pot ? Is it a bias setting ? How can I solve channel A issue ?
Thanks !