Maximum Input Voltage

Discussion in 'The Workbench' started by Tubeman, Jan 27, 2021.

  1. Tubeman

    Tubeman New Member

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    Greetings all. I have a mint unmodded 1977 JMP MK2 (2203) head and a 100 watt TSL combo. I also have a keyboard player who has recently modified his Hammond organs with a line out that comes off the pre-amp of the Hammond to a 1/4" line out. He wants to try it through my Marshalls. I don't want to blow them up. Is there a maximum input voltage that the amps can accept? It seems to me that a pre-amp into a pre-amp is way way more voltage than what they would be expecting. Any help is appreciated.
    Cheers
    Ron
     
  2. thetragichero

    thetragichero Well-Known Member

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    is it a line level output? how has the Hammond been modified?
    at the very least you'll want to use the low input
    you shouldn't run the risk of blowing anything in the amp (a distortion pedal can easily output a couple of volts), but it'll take some tweaking of volume controls to not sound horrible
     
  3. South Park

    South Park Well-Known Member

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    I would test it first with a small solid state amp first . The power levels may not match up right . It all depends on how the line out was built
     
  4. Tubeman

    Tubeman New Member

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    Hello. The Hammond line out is just taken off the pre-amp prior to the main amp circuit. The Hammond has a volume foot pedal which controls the pre-amp and I guess therefore the output voltage from that point. We did try it through a cheap Traynor transitor combo and nothing blew up. Would passing that test be good enough to try it on the Marshall's?
     
    Last edited: Jan 27, 2021
  5. South Park

    South Park Well-Known Member

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    Yes you can plug it in to the Marshall . Just turn it down first and go from thar . It sounds like it is a solid state organ . If it was tubes it would have a coupler cap in the circuit to block the DC and let the AC on to the amp
     
  6. Tubeman

    Tubeman New Member

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    Thanks for the replies. We'll try it. If it doesn't work I'll send my condolances to his wife.
    Cheers
     
  7. anitoli

    anitoli Well-Known Member Gold Supporting Member

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    If you over load the first tube you will get blocking distortion, the tube will basically shut itself down.
     
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