Looking for mod suggestions for a BF Bassman

[Lizard King]

 

As I described on another thread - I picked up a very clean 65 BF bassman.  The sticker said AA165 but it was an AB165.  I modded the power amp section to AA864 specs as described here: http://acruhl.freeshell.org/mga/main/AA864_vs_AB165.html
There are some other suggestions in a similar post at the Tone Lounge about changing some of the resistor values in the power amp section that I'll probably experiment with as well (tried to attach a gif on that).

That is a pretty easy mod and could be reversed....although if I ever sold it, I'd probably finish modding it all the way back to AA165 - probably be more valuable.

I am NOT going to drill any holes anywere in the chasis.  I will remove the ground switch and could remove one of the outputs to give me two holes to fill.

I'm looking for preamp distortion.  I'd like to keep the normal channel and change the bass channel into something with heavy distortion - eather as a separate channel or combined into a single channel with one of the bass knobs as a drive control.  I'm not sure if this is possible.  I know there is an unsed triode in there, don't know if anything can be done with it.  I thought of a tube buffered FX loop, ala blueguitar.org plans - i figured if I turned the amp into a single channel, I'd have a couple inputs and pots to ues for this - but then I read where these types of circuits usually sucked tone out of the amp.

I know a cathode from a plate and a resistor from a choke, but I'm not too big on tube theory - not sure how changing the value of a resistor in a feedback loop would affect the sound.

Any suggestions would be greatly appreciated - and I'm fully prepared to leave it alone and do nothing.  I have a blackstar HT-100 head which does the distortion thing very well....but if I sold it I could buy another guitar 

[thermion]

global/ local negative feedback smooths frequency response at the cost of some gain. removing this feedback will give a rawer, less refined sound, if that makes any sense. for some circuits, feedback is needed to keep things stable. the unused triode section can certainly be used for another gain stage; you will have to supply all the necessary parts along with real estate on the board for them to make it work. you will have to do some voicing/ tweaking to get it to sound like the blackstar's od channel (do you like the el-34 sound?).

[triode]

There was an article in the 80s guitar player that turned that amp into a seriously mooded blues breaker. I have a customer with one (with the mods)... it is pretty killer. Lots of tone stack mods and gain mods. You may want to look that up.

[Lizard King]

There was an article in the 80s guitar player that turned that amp into a seriously mooded blues breaker. I have a customer with one (with the mods)... it is pretty killer. Lots of tone stack mods and gain mods. You may want to look that up.

If that's the mod expanded on at the blueguitar.org, I did one of those on a mid 70's bassman....I don't think I'd tear up a '65 blackface like that...looking for something less extreme.

And the tube question...I'm not a fan of any particuar type of tube....I can't tell a whole lot of difference....I had a Peavy amp with EL84's I believe, not sure I ever played with EL34's....was going to mod out a blown Carvin 2 space rack amp with EL34's but never got around to it...chasis still sitting around somewhere.

[TIMBO]

Hi LK,I tried this in and unproven build and it sounded pretty good and it could be added/removed easily if you don't like it,same with the mosfet. The AX84 HI OCTANE adds in the extra gain stage via a pot ,something you could try. Thanks

[Lizard King]

What file type is .sch?  I can't open it with pdf

[Lizard King]

Still looking for suggestions.  I've read about something some people call an "Allen Mod"....seems they leave the normal channel alone and beef up the bass channel with different tone stack and use the unused half of the preamp tube...Can anyone point me to a schematic that does this?

Thanks.

I'm also thinking about adding the master volume mod attached.......AND I found the other schematic on the net....AND THEN I found a similar schemantic......any comments?

Thanks again