Ultimate Hammond Conversions thread

[maxkracht]

Thanks dragonbat, no need to make things any more challenging than you want to. You can get a great sounding amp out of a lot of old organs just by replacing some caps, slapping on input and output jacks, and maybe volume and tone controls.

The guy I have been making these things for is going to try and sell them for as much as he can, regardless of how nice they look on the inside, so I try and make things as good as possible out of respect for the end consumer. I see a lot of slapped together amp projects with visible problems selling to unsuspecting consumers for big bucks and I don't want to put any of that into the world. Gotta make stuff as reliable as I can so I can sleep at night. I also just like to design things...

[xk49w]

In 2009, I built a guitar amp for my nephew (in high school). I got the AO-35 from Bob Schleicher (RIP), the Oakland, CA Hammond organ super tech. I had done work for him for years (Leslie solid-state relay). I told him there were people converting AO-35s into guitar amps and selling them. He was way ahead of me. He'd sold a pallet of them to someone that was doing that. I asked him for one and he insisted on sending it to me no charge. Nice guy.

I don't recall what I based the schematic on. It looks like a mix of an AC10 and other designs. It has a cut control, no feedback, and a buffered tone stack. As to why I paralleled the two input stages, I had a spare one so why not?

The closed-back cabinet has a Jensen P12N behind a speaker directivity modifier (the donut shape behind the grill cloth).

[Coggins]

Going to have to read through this full thread as I was just gifted the guts of a Porta-B, including an AO-42, AO-43, AO-47, reverb tank, end block switches/pilot light/power switch, and some misc other parts. Already fired up the AO-43 and drove it from a rack mount preamp and it does it’s thing

[Coggins]

And to add insult to injury, I was just promised the Leslie 122RV guts that include a 40w 122 power amp, and another 18w reverb amp with reverb tank.

[10thTx]

I bought a Hammond AO-44 with the hopes of using ECL84's which didn't work out. So, I decided to make it a single ended amp similar to a Fender Champ but with a 5E3 tone stack. I was able to make this conversion fairly inexpensively in that I had a speaker, tubes, wood, grill cloth and many components left over from other projects. Maybe $185-200 total?

It sounds great! Very happy with it. Despite the exceptionally crowded chassis, it's almost dead quiet at idle. I'm thinking it's probably around 4-5 watts total? I initially tried it with NFB, but like it better without ......... so it currently doesn't have NFB.

I didn't want to use 6GW8 tubes as they aren't manufactured anymore and they're expensive.

Instead I used a 12AV7 in V1 and Tung-Sol 6V6 and a JJ EZ81. It has an 8 inch Weber Champ replacement speaker.

With respect, 10thtx