Question about the phase inverter channels inputs.

Discussion in 'Shock Brother's DIY Amps' started by stinga11, May 13, 2020.

  1. stinga11

    stinga11 TDPRI Member

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    Greetings, I am interested in building a clone of the Vox AC15 or AC30. The schematics I have found vary on how channel one and channel two go into the phase inverter. Even the handwire version and the PCB version also vary. So can someone explain to me what is the difference? If one of the two is better than the other.
    [​IMG]
     
  2. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

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    I would have to see the rest of the preamp cicuits.

    I assume the difference would be: in order to use both channels at the same time they would need to be in phase.
    The upper diagram has the preamp signals in phase and they are mixed together through the mixing resistors.
    The lower diagram the signal are out of phase and use the opposing sides of the phase inverter to put them in phase.
     
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  3. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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    One of the inputs will be inverted, the other one won't. So which one of the two circuits you should use depends on the (relative) phase of the two input signals.
     
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  4. stinga11

    stinga11 TDPRI Member

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    To make these schematics I used the one for the VOX AC15 hand wired and the one for the VOX AC15 PCB.
    [​IMG]
    [​IMG]
     
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  5. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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    If you want to use both inputs at the same time, use the top one. The extra gain stage inverts the signal, the following buffer doesn't and then the ltpi mixes them with again an inversion resulting in both signals exiting the ltpi in phase with each other.
     
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  6. stinga11

    stinga11 TDPRI Member

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    Thanks for answering. The top one is as is the schematic of the modern version of the hand wired AC15.
     
  7. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

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    I agree with Tom.:)
     
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  8. stinga11

    stinga11 TDPRI Member

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    Which of these two master volumes do you recommend?
    Type-2 Lar-Mar Master Volume
    [​IMG]

    Frondelli Master Volume
    [​IMG]
     
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