Grateful Dead Music Forum

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Chat about Equipment Info
 #91595  by sants
 Mon Jan 03, 2011 10:13 am
I figured I would start here because we have some knowledgeable people.

I searched all the organ forums and coldn't find the answer I was looking for.

My keys player has a hammond m3 we are going to chop to use live and run through a motion sound setup. The problem is that I need a line out and this m3 has the old field coil speaker. I would need to dummy load the field coil with a 20 or 25 watt 700 ohm resistor which are proving very hard to find. I then need an out box which is about $80.

Option 2 - There is an rca input on the volume pedal block that can be easily be rewired to be an out because the preamp runs through the volume pedal. The input is originally there so a record player or outside source can play through the organ for practice.

My question in short- can I do the preamp out mod to the rca input, yank the speaker and just pull the power tubes from the amp so I won't have to worry about finding the right resistor or buying the $80 output box.

Starting thinking of Jerry's twins and Mc2300 so I figure I could do it with the hammond.

Any thought?
 #91609  by Cmnaround
 Mon Jan 03, 2011 2:36 pm
I think you need to buy the right kit to get the line out - same kit you would use to hook up a Leslie. They are like 100 bucks or so. Save yourself the trouble and get him to buy a Nord - weighs like 17 pounds, has awesome Hammond and rhoades sounds.
 #91621  by JonnyBoy
 Mon Jan 03, 2011 6:54 pm
I am not claiming I know where the tap it, but I am sure there is a tap point in th preamp section that can be sent to a 1/4 jack. The deal is finding it. On a twin it is within the circuit with the final preamp tube comming off the tube output, but usually up the line a few resistors or caps from it, not directly off the tue itself. Maybe an organ expert can help you there to find the right point. Just thinking.... Good luck...JB
 #91625  by sants
 Mon Jan 03, 2011 7:23 pm
Thanks guys!

Johnny, there is a preamp line coming out to the volume pedal and then back into the power amp. I was thinking if I rewire it at the pedal box I can just take that line out from the pre. My only concern is not having a load on the amp if I ditch the built in speaker. If I pull the power tubes do I have to worry about a load on the amp. Like how Jerry had the power tubes pulled from the twin.

Have been asking the organ guys but not to much info on this.
 #91626  by Reefer Gladness
 Mon Jan 03, 2011 9:08 pm
Carl Boeman is the Hammond man. He has done extensive work on my brother Mike's B-3 which has a 100 watt Dumble power amp in an anvil case. Loudest B on the planet. The amp is so powerful Howard put a Navy klaxon horn in the Leslie because the Hammond drivers kept blowing out.
 #91627  by waldo041
 Mon Jan 03, 2011 9:30 pm
pulling the power tubes is going to raise voltages in the preamp and the filter caps should be rated for the increase. but pulling the power tubes should render the power amp section dead, but if it is not shunted to ground it can produce noise with some of the components still "in circuit". a schematic is always helpful when seeking advice on do's and dont's of the gear in question.