Hammond AO44 to "near-Match" Spitfire

[chris937]

I snapped a key contact in my second craiglisted $50 M100 while attempting to adjust the bus bars. Since I'm getting an M3 this week, I made quick use of the parts.

This was a sister build to the other AO44 amp. I reused the PT, OT, chassis, 6CA4, and 6GW8's adding a 12AX7. Circuitwise, it is darn close to a Matchless Spitefire with a few substitutions based on what parts I had on hand.

Pics 1 & 2 show how far I stripped it down. Sometime long in the past there was trouble near the rectifier and a repair was made. Everything worked quite well before teardown thankfully.




Test fitting the parts.



First test run and it was too much amp for the C12R. It's now sporting a screamer of a ceramic speaker I pulled from my CL'd Leslie 225.



This amp was a fun build and challenge to layout but fired right up the first try and sounded so dang good doing it. I sometimes think I go overboard with the shielded signal wire but the amp is dead silent despite the very close quarters.



Next up on my list is a Conn 541 amp to bass amp conversion. I'll try to document it a bit better.

[Pdavis68]

Aren't you short a 12AX7 for a spitfire?

I have a Davis 201A PA that I need to convert to a guitar amp. It's got 2 EL84s and I was going to replace the 6EU7s with 12AX7s. Maybe a spitfire circuit would be a good one to follow. I think the voltages off the transformer are within about 10V of the spitfire... It has three 6EU7 sockets, so I might even be able to add tremolo and reverb...

[chris937]

Nope! I'm one of the 6GW8's triodes (equivalent to a half 12AX7) for that first gain stage and using the 12AX7 I added as the phase inverter.

[Pdavis68]

Doh! I forgot you mentioned the 6GW8s. So you've got a spare triode from the other 6GW8. If you've got the current to spare, you might want to add a tremolo. Pretty simple circuit and it only requires a single triode.

I have a little amp with a 6GW8 SE (somewhere in the 3-4W arena). It's a nice sounding little amp.

[chris937]

You know, I'm not particularly inclined to squeeze anything in there that I already haven't. This was my first time using 6GW8's but I like them. I still have the pair and OT from the other AO44 I should do something with.