Preamp Poweramp swapping

Discussion in 'Marshall Amps' started by mad5066, Dec 1, 2020.

  1. mad5066

    mad5066 Well-Known Member

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    Assuming both amps have an FX loop, is it safe to send a preamp signal from a larger 100watt head into the poweramp of a 20 watt head? Is there anything I would need to be aware of?

    For this example, I'm wondering how my 6100 head would sound through either the sv20h or 2525h. I think it would be fine but figured I'd ask first before I try and fry something because of something I didn't think about. Actually sounding good is a whole other thing but I figured it would be safe technically. I know it would be the fx loop send of the preamp to the fx loop return of the power amp.
     
  2. The Dose of Harmony

    The Dose of Harmony Well-Known Member Gold Supporting Member

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    I think its safe!
    But i only have 100 watts heads!

    if you follow the path
    its guitar signal that you are re routing (send form fx loop of Head # 1) from one head to another ( return of fx loop Head # 2).

    just put the master volume on both very low and increase little by little!
     
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  3. RLW59

    RLW59 Well-Known Member

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    What you propose is safe and works fine.

    But on most loops, if you plug into the send of the first amp that won't break its connection to its power amp. So the first amp will still be blasting sound from its speaker while also sending a signal to the return of the second amp.

    To silence the first amp, stick a shorted dummy plug into the first amp's return jack. If you don't have a spare plug to use as a dummy you could just stick one end of a cable into the return jack (with the other end not plugged into anything) -- you may get some hiss/buzz/hum out of the first amp's speaker, but it'll be pretty low level and at least you'll only have guitar from the second amp's speaker so you can determine if getting a dummy plug is worthwhile.
     
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  4. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    pull the power tubes from the 6100...
     
  5. assquatch20

    assquatch20 Active Member

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    It won't damage anything but it depends on the amps and their loops whether or not you'll have the master amp stay running. Some can run their preamp in standby, others have a master volume that will allow the preamp signal to be retained while cutting the volume to the power section, and some do both. Then the slave amp will probably work with something in its return but sometimes they need something in their input if it's a switched jack. Then there's series and parallel loops but that's not as relevant here. It's safe so just give it a try and see.
     
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  6. SkyMonkey

    SkyMonkey Well-Known Member

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    I can attest to this.
    I ran a few configurations to test an observation by someone that the new DSL Loops were 'Parallel'.
    He thought it was a parallel loop because he was still getting sound from his 40CR whilst running the Send to a slaved amp.
    Just connecting the Send only acts as a signal splitter.
    It doesn't engage the FX Loop (i.e. it's still bypassed).
    Only connecting the Return engages the series FX Loop.
    And only when the Loop is engaged can you use it to control the signal going to the power amp.

    For this sort of thing I use Headphone jack adapters as dummy leads.
    They have no 'lead' to act as a noise antenna, so are almost silent (IME).

    HPAQA1-large-200.jpg
     
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  7. mad5066

    mad5066 Well-Known Member

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    Great, thanks for all the responses! I'll use the headphone jack in the 6100 return and also a dummy load because I only have one speaker cabinet. Hopefully I'll have time this weekend to try it out and see how it sounds.
     
  8. assquatch20

    assquatch20 Active Member

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    That was me. I actually might be using that method for wet/dry this weekend. Depends how much space I have.
     
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  9. David Harris

    David Harris New Member

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    I've been doing some thing similar. Guitar into drive pedals, then front of Mesa TC100, fx send to stereo delay, out of delay to fx return of the Mesa and the fx return of a Ceriatone. Ceritone has PPIMV that allows me to adjust volume of the power amp to match the volume of the Mesa.

    Sounds awesome!
     
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