Ceriatone Forum

hello all. This is my first post,  and I am new to the inner workings of tube amps, but I have already learned alot just by reading the posts here :).
I am working on ordering a 1986 bass plexi. I've been discussing several mods with Nik that I want him to build into the amp and I wanted to hear what you all think of them:

1) Add a .68ufcap on V2 cathode ala plexi (lead) and wire it to a push-pull bright vol. pot to take it in and out of the circuit.

2) Add a .68uf/2k7 to V1 cathode and make this also switchable via a push/pull normal vol. pot. My question here is how will this sound, being it is shared cathode? ??? Maybe It would be a good idea to put a switch on the back for shared/splite cathode? :-\

3) Push Pull bass pot to defeat the tone stack. I read about this mod being done on 18/36 watters, but Has any one done this mod in a plexi? What would this effect the tone, gain etc.?

4) Negative feedback switch to turn NFB on/off , and a 27k NFB resister with a 5ok pot on back panel to adjust NFB. Again I've heard of doing this mod to 18/36 watters, but not sure what to expect with a plexi. Has anyone done this one?

5)Ext bias mod + switchable bias resisters so i can switch from el34, 6l6 and 6550 tubes with only a bias pot adjustment.

If anyone has any comments or suggestions on these mods I would love to hear them.

Thanks!

I know this is a bit late, but did you order it to fit 6550s?

I would like to get an 86 with KT88s, and since KT88s and 6550s are swappable, i wonder if you've done it.

As for the questions, for

3) Removing the tonestack will give the amp more gain as I've read through the forums. Especially on AX84, where they mentioned the tonestack sucks a lot of gain from the circuit. Ditto with the OTS, the preamp tonestack bypass will boost it quite a bit.

As for external bias, its very useful, no need to remove the chassis and everything to test and adjust the bias.