Musicians Roadhouse

Hi all
I am planning on retubing my YJM 100 with NOS glass. I understand that one of the four preamp tubes toes not really effect tone (something to do with the reverb iirc) and, if that is the case, I do not want to put expensive glass in there. I believe that this is V3 (the third from the left, I thing) Can anyone confirm this or tell me which tube serves this non-tone function.

Thanks

V1, V2, V3 operate the same as any 1959 amp, the fourth preamp tube in V4 compensates for any volume lost while the noise gate and reverb are engaged.

Thanks so much Surf. I am getting 2 Brimars, 1 Tungsram, 1 RFT, 1 BEL, 1 pre-war Ei, & 1 Matsushita NOS and will be rolling them in V1-3 to determine the best mix. Those that do not make the cut will go into my ENGL Blackmore.

You might also experiment with different power valves, that could really change up the amp. The YJM can autobias most powervalves.

Thanks Surf. I did that a few years ago after reading up on it and ended up with NOS Siemens El 34s.