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 Post subject: Hammond amp
PostPosted: Fri Sep 09, 2011 10:20 am 
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Joined: Tue Apr 15, 2008 10:48 am
Posts: 119
Location: Winchester VA
Greetings, Trinity friends!

It's been a while since I last posted, after building a Deluxe and a TC-15. I recently purchased a Hammond M-3 organ with AO-29 tube amp enclosed (and original Jensen field coil speaker). Date of manufacture appears to be 1955. After replacing most tubes and cleaning it out, it sounds very good. But I'm trying to decide the best way to wire in a line out for Leslie or PA connection.

The web has several suggested circuits, but all I've found involve connecting at the speaker, thus after the power amp and OT (with necessary resistors and hum-reducing cap). It would seem much better to find the correct place between the preamp and power amp sections, wiring in a circuit breaking jack at that point. Any advice where I should look to find that spot? And if I would need to add any components there for the line out? I understand a little about tube amp theory, but obviously not enough to figure this out on my own!

It appears to be a straightforward push-pull amp, using 12AX7, 12AU7, 6BA4, 6AU6, and 6C4 tubes; 5U4 rectifier. Power tubes are two 6V6. There is no adjustable tone circuit as on a guitar amp, but of course there are drawbars controlling various frequency ranges (fundamentals and overtones of the keyboard notes).

I do have a good copy of the amp circuit.

Many thanks!

Jim


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 Post subject: Re: Hammond amp
PostPosted: Sun Sep 11, 2011 3:39 pm 
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Joined: Fri Mar 14, 2008 12:05 pm
Posts: 432
Location: Massachusetts
Hey Jim! Seems everyone has an M3, aka "the Poor Man's B"!!!
I've always used this light bulb circuit that was posted in Keyboard Magazine a hundred years ago. (At the time anyway) it sounded great through my ADA Flanger and right into my system. It is right off the speaker though, which I'm fairly certain is the way that Leslie always did it. Very cool organ even though it only goes down to a low "F". Great for Long Time, not so much for Green Eyed Lady :|

Joe G


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