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Switching Between Combo Preamp and Hammond

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  • Switching Between Combo Preamp and Hammond

    I am looking for something which would:
    • receive a six pin connection from the Hammond A-100,
    • receive a six pin connection from the Combo Preamp and,
    • allow me to select by switch(es) one of the two sources,
    • output the selected source with a six pin connection to the power relay for the Leslies.
    This will allow me to use my Combo Preamp or my Hammond A100 with my 147/247 Leslies without having to unplug and replug cables every time I want to switch source.
    Rheem Mark VII, CEI Madrigal, 1969 Leslie 147 RV, Leslie Combo Preamp. Soon to add Hammond A100 and Leslie 247.

  • #2
    Or you could plug the other instrument into the RCA jack on the A100 preamp's expression box, and play both through the Leslie at the same time.


    • #3
      It seems possible.

      But the mains power (Pin3 and 4) and the speed control (Pin2) cannot come from 2 places at the same time.
      It will be necessary to choose where the power comes from. For example the preamp.
      And add a small relay into the pedal to decouple the speed control from the A100.

      It's a small electricity problem.



      • #4
        The contraption you've described does not exist, that I know of. One would have to build it.

        What is your actual problem that you are trying to solve?

        The question implies that the organ is with you at the same time and in the same room, and you don't want to use the organ's speed switches while playing non-Hammond source.
        -- If you don't mind using the organ's speed switch, connect the other instrument signal into the RCA jack of the organ preamp, as suggested above.

        That said, if you need a foot switch to be away from the organ, you could construct a foot switch, and connect it in parallel to your existing organ speed switch. Be sure all of the wires are insulated and the switch / enclosure is rated for 120V. Connect the foot switch via something other than a 1/4" jack to prevent people from mistaking it for a line out and smoking their equipment. (Disclaimer - this requires electrical safety, thought, and care to be done effectively.)

        The safer route is to construct a 1/4" line out from your Hammond, and use the Combo Preamp exclusively for both signals.


        • #5
          I'm looking to use my combo organs through the Combo Preamp and the Hammond plugged in the traditional way but not play both at the same time. The switch would isolate each input from the other, along with their speed controls. A/B source switch.
          Thanks for advice and the alternatives.
          Rheem Mark VII, CEI Madrigal, 1969 Leslie 147 RV, Leslie Combo Preamp. Soon to add Hammond A100 and Leslie 247.


          • #6
            I built a Leslie switch box using 3 DPDT relays. Worked just fine.