MKII A converted to simul class preamp tube question

[antennahead]

I have a MKII A that I've owned since new, build date 1979. In 2001 I sent it back to Boogie and Mike B. converted it to simul class for me, as well as replacing the EQ sliders and some noisy pots, etc. Prior to the conversion to simul class (former 60/100 watt option), V4 (the reverb driver) took a 12AT7. I've noticed in the owner manuals for the later simul class amps (MKII C and MKIII) that they are using 12AX7s in all sockets, including the V4. I'm having a hard time getting anyone at Boogie to return my call or emails with this question................ looking to re-tube and was curious if I need to go 12AT7 or 12AX7 in V4. Thanks!

John

 

[mark2boogie]

Hi John,

Have a test : a 12AX7 instead of a 12AT7 and vice-versa will not damage your amp. The performance may be modified, or at least the tube would last lesser... If you can do it, trace the schematic of your reverb driver's amp and compare the values with simul-class and non simul-class amp schematics : you will know which tube to use. My MKIIA has the 12AT7, and I converted my now sold MKIIB from 12AX7 to 12AT7 reverb driver, finding that the tone was cleaner, deeper, less metallic...

A+!