WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
Pls check old issue Glass audio, it has this schematics (line amp only), it use 6DN7 and 6SN7(or 6SL7, I'm nor sure). It is a MFA Luminescence model A, it has 3 versions: A,B and C, they has a little bit not similar.
I have in my system this absolutely fantastic preamplifier !
and good news for you i have the complete documentation !
i can make you a copy and send by postal way if you want.
Probably you can help me ... i replaced the 6922 tube in preamp by others 6922 but ..... in the power supply box there is a big rectifier tube called 9330 from penta laboratories ! impossible to find it , so is it the good reference ? no informations in the documentation .... all schema for preamp box but no details about the last tube i would like to replace .....
and internet site from pentalaboratories.com don't react .....from France ! ( you could try from another location ?)