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Hammond A-100 bass heavy sound

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    Hammond A-100 bass heavy sound

    I have a Hammond A-100 connected to a Leslie 145 via a 26-1 kit. I have half-moon M/E/E and C/T switches. Everything is connected and working in the normal way (26-1 audio connected at AO-39 amp). I can switch between the Leslie (Echo), organ speaker (Main), and both (Ensemble). Chorale/Tremolo switch is working fine. As I have read (and observed), the AO-39 has a bass-heavy sound. I understand the AO-28 connection is normal/brighter. Is there a way to use the AO-28 connection point, while maintaining the same M/E/E functionality?
    Last edited by sdemers; 02-13-2020, 01:11 PM.

    #2
    Short answer, yes definitely. However, the method I’m thinking of involves reconfiguring the switch wiring completely different from what the 26-1 box does. Perhaps others already have a simple documented scheme for doing this. Also, there is a simple mod you can do to the speaker amp to brighten it up, just snipping two little capacitors underneath the chassis. You might want to try that first and see how it sounds. I did this to my A100 and also wired the switch to feed the 145 directly from the preamp.
    Tom in Tulsa

    Fooling with: 1969 E100, 1955 M3, 1963 M100, Leslie 720

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      #3
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        #4
        Much prettier version than what I would've drawn on a napkin!
        Tom in Tulsa

        Fooling with: 1969 E100, 1955 M3, 1963 M100, Leslie 720

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          #5
          Thank you. Tpappano, can you tell me more about snipping to capacitors on the AO-39 please. Also, Valotus, could you elaborate on the diagram above please.

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            #6
            On the AO39 there are two .1 mfd capacitors, C1 and C10, each in series with a 10K resistor. These create a treble roll-off characteristic for the amp. Disconnecting one end of each of these caps (or the series resistor) will flatten the response, bringing up the highs.
            Tom in Tulsa

            Fooling with: 1969 E100, 1955 M3, 1963 M100, Leslie 720

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              #7
              Thank you tpappano. Regarding the wiring diagram above, Will that keep the same M/E/E switch functionality, switching between the Leslie and organ speakers, or both together?

              Sean

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              • valotus
                valotus commented
                Editing a comment
                Yes, that's the idea. You need to figure out from your switch contacts what goes where in certain positions, but after that the schema is simple. Far left position is Main; switch shorts leslie input and ground but doesn't affect what goes from preamp to AO-39. In the middle Ensemble position both amps get signal. When switched to right as Echo, leslie amp still gets signal taken before 820 ohm resistors, but AO-39 input is shorted after those.

              #8
              Yes, it will provide the same speaker switching, the difference is that the Leslie now gets its signal direct from the preamp instead of the AO39 output.
              Tom in Tulsa

              Fooling with: 1969 E100, 1955 M3, 1963 M100, Leslie 720

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                #9
                Thank you Valotus. So the 820 ohm resistors need to be added/inserted into the wiring?

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