Speaker Tap Box to drive 2nd amp

Discussion in 'Amp Central Station' started by noname_dragon, May 13, 2021.

  1. noname_dragon

    noname_dragon Tele-Holic

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    Can anyone decipher this circuit? Built for me back in the 90's by the late Sal Trentino of San Anselmo CA.
    I asked him how to run my Princeton Reverb into a bigger amp for more volume on stage without changing the original IMG_1830.JPG IMG_1831.JPG IMG_1832.JPG sound. He said sure... I'll build you one like Neil Young uses on his Deluxe.
    The hookup is: run speaker cable from PR speaker out to the box input and speaker out back to PR speaker. Then line cable out to 2nd amp. Lift ground on 2nd amp. Adjust output control.
    It works good. It looks very simple inside the engine room, only 3 doo-hickeys in shrink tubing. What is going on in there in basic terms? I searched and can't find anything else quite like it.
    Is there a better way to do this?
     
  2. W.L.Weller

    W.L.Weller Tele-Holic

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    The three doo-hickeys are probably resistors, along with the variable resistor (level control) You can cut off the shrink tubing if you want to be sure or make a clone.

    In basic terms, a speaker-level signal has enough current (the "volume" of electrons when people use water flow to analogize electric flow) to make a speaker cone move. The resistors are reducing that current so that the signal can be sent into another input without blowing anything up.
     
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  3. Peegoo

    Peegoo Poster Extraordinaire

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    Also, do not run a speaker level signal into a mic/guitar-level or line-level input on an amp. You'll fry the amplifier.

    Here's the typical layout necessary to make a little box that converts a combo amp's speaker level to a line level.

    WARNING: this requires your amp to have an extension speaker jack on the chassis. You have to have the speaker always connected to the amp or you risk damaging the amp's output transformer. Do not disconnect the onboard speaker.

    [​IMG]

    If you don't have an extension speaker jack on your amp, you can modify this layout by using alligator/crocodile clips to connect directly to the speaker terminals in your amp like this:

    [​IMG]
     
    Last edited: May 14, 2021
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  4. Peegoo

    Peegoo Poster Extraordinaire

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    Using the above as a guide, it's probably this:

    [​IMG]
     
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  5. noname_dragon

    noname_dragon Tele-Holic

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    Thanks Weller and Peegoo. In an age of complication, it's neat to see a simple device that works well. I also use a Radial Switchbone to run 2 amps but that's a different scenario. I recently got a 5E3 and want THAT sound reinforced for some outdoor gigs this summer... probably into a SFVR
     
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