AA864/AB165 hybrid Bassman - who's got one?

[justinbelshe]

I'm trying to build one of these, but it's difficult for me to do without a layout diagram (I'm sort of retarded like that).

Does anyone here have one of these? I've been looking online for photos of this circuit but I've had no luck so far...

Any help would be appreciated!

[Satamax]

Have you checked this one?

http://www.schematicheaven.com/fende...a165_schem.pdf

[justinbelshe]

Originally Posted by Satamax

Have you checked this one?

http://www.schematicheaven.com/fende...a165_schem.pdf

I have layouts for the AA864 and the AB165.

I'm looking for the hybrid circuit from Andy Ruhl's recipe: http://blueguitar.org/new/schem/fend...4_vs_aa165.pdf

[justinbelshe]

Thanks to everyone for playing, but today's winner is JERRY SHAW! He wins my eternal gratification for sending me about 30 pages of notes, among which was this diagram:



I looked at it, and it suddenly made sense. I ran out to the shop and pulled that pair of 220K resistors and put in a .001uf cap. I plugged it in, biased the tubes, turned it on and it was DEAD QUIET! I was afraid that maybe it wasn't passing signal, there didn't seem to be any hiss. I plugged my "Test Probe" guitar in was blown away!

http://youtube.com/watch?v=GnS4KEFMQKI

(Yes, I know the guitar is out of tune...)

The normal channel seems to have more gain than the bass channel, but I only played through each one for a minute (it was 1:30 in the morning).

[bassstrat]

Thanks For Posting This! I Sent You A E-mail About Possibly Getting Some More Info,if Possible!thanks,daryl....

[jdezubel]

Hello,
I've been spending way too much time researching whether or not I should proceed with attempting to do the hybrid blackfacing modification to an 1971 Bassman that I recently obtained. Based on photos from other bassman circuits I'm pretty sure the circuit I'm working with is an AB165. A biasing and cap job was done in 2001 as was made clear by an inscription inside the chassis. I do not know if other specifc mods were done.

I am located in Tucson, Arizona and was hoping that perhaps I could get some help from Andy Ruhl. Based on my research it seems like he may be teaching here. Unfortunately, it also seems like he no longer wishes to do amp modifications? I'm a civil engineer and have not looked at circuits since college. The last thing I want to do is screw up what I am hoping will be my main amp choice from here on out.

I'm also a bass player in Tucson and could use some help with a power diminishing/surge/popping/static problem that caused me to think I had blown the speakers in my Bergantino NV610 cabinet with this Bassman. I regularly gig with my bandmates 68' Bassman with an Avalon U5 DI/preamp between the bass and the amp sounding through the 4ohm cabinet mentioned. I have not experienced any problems, but only perfect tube tone with that setup and would like to come close to that tone with this 71' Bassman. Any help would be greatly appreciated.