Replacing the Hammond M3 Amplifier with H-AO-28

[Alek Z]

I've had an M3 for about 6 months now, I like this particular one quite a bit, and took me two weeks to repair the switches, gummed up TG, and defective power cord. It really does sound great like a Hammond, especially through my Leslie 145. However, I can't help but notice it just doesn't quite sound like a B3, obviously. This is however the closest I've ever come and I'm always thinking of ways to improve the M3. My most recent thought, would be to rewire the percussion which already has the same tubes as the B3's H-AO-28. Then I thought, why not just replace it with an H-AO-28? I've seen them go for under $200, and after selling the H-AO-29 that would come out of the M3, I'd be set back less than $100. I think that this is a worthwhile improvement, if it really does give it THAT sound that we all love. It seems to be the only real electronic difference between the B3 and the M3. Of course there's the preset keys, switchboard, longer manuals, better vibrato and more tonewheels, but with the H-AO-28 and the M3's TG, I think I'd essentially have a pretty close replica of the B3 sound for what I have to work with. Add some foldback on there and I think I could get some pretty great tones out of this M3. Is this something that I could feasibly do? It doesn't seem to be to crazy of an idea, and I've already got the power amp in my Leslie. The expression pedal setup seems like it would be compatible as well given the close similarities in structure of the 28 and 29. I couldn't find much about this but it seems like a good idea. Let me know what you guys think, I will be studying some diagrams as well, thanks!

[tpappano]

I think the AO28 and AO29 have pretty much identical preamp sections, hardly seems worth it to swap amps. One difference between the M3 and B3 would be the foldback and tapering of the B3 manuals. The upper end of the B3 keyboard has tones that the M3 does not, but if you like projects, you can add them. Another issue might be the filter capacitors on the TG. If they are original they probably changed value and the higher tones likely aren't as bright as they might be. *Lots* of posts on this forum about all this stuff 8) I have a M3, M100 and lately an A100 (essentially same as a B3) and I wound up changing the TG capacitors on all of them, all three organs just sounded dull.
Enjoy your M3!

edit: Also, the vibrato line box capacitors probably need to be changed too. The vibrato may sound 'odd' from too much frequency shift.

[Alek Z]

I've done a lot of research and the TG recaps don't seem worth it to me personally, but certainly a good idea to recap the vibrato line though my vibrato doesn't sound too bad. I also have been toying around with the foldback idea, I'll probably do it later on for at least the higher tones on the upper manual, I just hate soldering haha. Anyway, thanks for your feedback on the idea, and enjoy your A100! I'm jealous! almost got a free C3 recently but I guess the guy figured out what it was worth 3 hours after telling me I could get it, just needed to get off work and I'd have had it....

[enor]

If you change to an AO-28, you will lose the bass pedals.

[bourniplus]

Indeed you might lose the pedals, although I remember seeing a post where someone managed to wire them back in the circuit. But I think you'd still lose the legato function.

Where can you find an AO28 for under 200$? I often look on ebay and don't see many, and usually I see them for much more than that. I'd like to find one myself for my X77.
There was a post on the Hammond yahoo group about "how to B an M" that talks about the modifications that can be done to the AO29 to bring it closer to an AO28. If anyone is interested I'll copy/paste it.

[Alek Z]

I am definitely interested in that Yahoo group, if you could provide it that would be great! The AO28 I found was on eBay, but looking again I guess it's already been taken down or sold :/

[enor]

Indeed you might lose the pedals, although I remember seeing a post where someone managed to wire them back in the circuit. But I think you'd still lose the legato function.

It could be done, but you'd need:
* the pedalboard from an L-100
* another set of M drawbars (or similar, in order to incorporate a true drawbar for the bass pedals)
* rewiring and recalibration of the tone generator

[David Anderson]

The reason the M3 doesn't sound like a B3 is the complexity of the manual wiring. I also doubt that substituting an AO28 will make much difference for the reasons already stated. Much of the circuitry is the same.

[Alek Z]

Thank you all for your responses, was an idea for just getting closer