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Hammond Organ amp to guitar amp
Hammond Organ amp to guitar amp
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Old 17th December 2010, 04:47 AM   #1
sledge57 is offline sledge57  United States
diyAudio Member
Join Date: Dec 2010
Default Hammond Organ amp to guitar amp

Hi I have an amp from an old Hammond Organ (L100 I believe)

Someday I'd like to make something along the lines of a Marshall 18W clone.

For now however I'd just like to get it working pretty much as it is.

Any suggestions on where to start would be appreciated.

I haven't built any amps yet however I am an electronic tech, unfortunately tubes were not part of the curriculum when I was in school.

Also about to mod a Blues Jr, Billm mods + a VVR3 when they arrive.

Thanks for any help you can provide.

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Old 17th December 2010, 02:10 PM   #2
ratbagp is offline ratbagp  United States
diyAudio Member
Join Date: Mar 2008
Location: North East, MD
You might find this link useful. A couple of the posts show schematics.

Hammond L-100

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Old 17th December 2010, 11:08 PM   #3
mashaffer is offline mashaffer  United States
diyAudio Member
Join Date: Jun 2004
Location: Indiana
I think as a first go at it I would...

1. Disconnect the feedback loop (goes through the factory gain adjustment pot).
2. Remove the key click compensation cap (in parallel with the anode resistor of the VAS just before the PI.
3. Inject your signal right after the spring reverb and rewire that first 12AX7 as a simple CC gain stage as in most guitar amps.
4. I would probably put a simple volume pot before that first gain stage just to get it working.

After this you can work at making an actual 18W ish type as everything you need is there IIRC. You could even go with a more complex front end later with TMB stack and extra gain stages.
The only reason I drive the 91 Colony Park is that I can't afford a 65. Me old school? Couldn't be.
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