Blackface Bassman Allen Mod?

Got a 66 Blackface bassman, need a schematic for the Allen MV mod, which changes bass channel into jtm45 zone and normal channel becomes better too.

For whatever reason this message board typically ends up being the most helpful and knowledeable ao thanks in advance!

Oh.... and a guitar amp tech in southern california who can do it.

Sorry I'm not familiar with the mod you refer to so can't help with that but a 66 Bassman could be one of 3 different circuits, AA864, AA165 or AB165 so this may be relevant when modifying it.

Maybe a derail, but an AB165 that is properly biased (maybe ditch the extra NFB) is one of, if not the most underrated vintage amps out there. My ears prefer it to a "JTM45," but I digress...

Mod it all you want, but you're still dealing with Fender Blackface era transformers, voltages, rectification, etc. It's just not going to truly cop an early Marshall tone, nor (imo) a particularly interesting hybrid of the two amps. There's a lot of better, modern alternatives if you want a JTM45 style amp, which will be a better representation or interpretation of an original '45.

If you want to go MV, look at a PPIMV. My results have been less than great when using MV in BF amps, but others make it work. Looking at attenuation/voltage regulation are other options that can be used in conjunction with a MV.

If it's an AA864 or AA165 I strongly suggest you leave it stock. These Bassman iterations are rare and worth some money.

I know Allen designed/built amps have fans...I'm not one of them. I've tried playing through about 3 of his models and have listened to recordings/clips of a couple others. I've not yet heard anything that impressed me positively. The RAW circuit, for example, is something I found almost useless, sounds like poop AFAIC. There are so many other guys out there who have their own "take" on Fender amp circuits that I find way more musical / useful. Just MHO, FWIW...

PaulD said:

Sorry I'm not familiar with the mod you refer to so can't help with that but a 66 Bassman could be one of 3 different circuits, AA864, AA165 or AB165 so this may be relevant when modifying it.

Click to expand...

Its ab165 I think I found the mod. Bass channel sounds like crap stock normal channel is nice. I'm definitely nodding. I'll post some sounds when done

A real super easy mod is pulling the first preamp tube V1. The bass channel will be inoperable but it increases the gain in the normal channel.:salude