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Standalone Reverb unit build

Discussion in 'Glowing Bottle Tube Amp Forum' started by JustLetMePlay, Nov 8, 2020.

  1. JustLetMePlay

    JustLetMePlay TDPRI Member

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    I have a transformer for a fender reverb unit lying around and it's time I finally use it. The question is, does it have enough juice to power a (Harmonic?)tremolo+reverb unit, or just the stock reverb?
    Potentially I might just take a Super/Princeton Reverb+tremolo circuit, as they just use 12ax7 instead of a 6k6 tube, and (I think) this would reduce current draw enough to use?
    Thanks in advance, and I hope you're all doing well
     
  2. radiocaster

    radiocaster Poster Extraordinaire

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    I think it'll work, but you need a different output transformer.
     
  3. JustLetMePlay

    JustLetMePlay TDPRI Member

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    I've got a 1750A, with a primary of 23k, which would match up with a 12at7 reverb driver tube. So I can build the reverb component, just not sure of the power requirements is all. With standard trem being 1 tube, harmonic would be 3, plus the 2 for reverb.
     
  4. radiocaster

    radiocaster Poster Extraordinaire

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    The heater current is 300mA per tube. The plate current is pretty low, although you may have trouble there too.

    I think you might not have enough juice for the heaters. Do you have the exact specs of your transformer?
     
    Last edited: Nov 8, 2020
  5. JustLetMePlay

    JustLetMePlay TDPRI Member

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    it says 237V @50mA, and heater current of 1.05A (6.6V). Leaving only room for 3 tubes. Maybe I should use a solid state lfo, with a tube driver for the trem, leaving an extra tube for a buffer/extra gain stage? Using a MOSFET I could have a low current lfo. Has this been done before/Is there an easier way?
     
  6. separateness

    separateness TDPRI Member

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    I rebuilt my Twin from the ground up a few years ago and implemented a solid state oscillator. It works very well. I even have an led on the panel that blinks in time with the trem. It was based on the attached circuit which I believe I found on the ax84 forum. It applies the trem to the output section bias but I am sure you could scale the voltage to whatever point you are applying it to.
    I myself have for a while now intended to move the application point from the output bias to the cathode of the preamp section just before phase inverter, but I have not done so.
    Screen Shot 2020-11-08 at 9.19.49 AM.png
     
  7. JustLetMePlay

    JustLetMePlay TDPRI Member

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    Last edited: Nov 8, 2020
  8. JustLetMePlay

    JustLetMePlay TDPRI Member

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    Last edited: Nov 8, 2020
  9. JustLetMePlay

    JustLetMePlay TDPRI Member

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    Thanks! I might use the output to drive a trem bug ab763 style. Also how did you mount the transistors to the turret board? Some nice socket, or just direct to the turrets?s Also should I close this thread and start a new for the build or just keep this one?
     
  10. separateness

    separateness TDPRI Member

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    I actually had a (gasp) PCB made. I might be able to dig up the files for it if you like, but no guarantees. I don't know how easy it is to get a PCB made down under but it was about 30 bucks for three of them for me. Heck I might even be able to find one of the spare PCBs, but again given the general state of disarray in which all of my personal tech stuff is wont to be, it is crapshoot whether I might find one. As to whether you should make a new thread or not, perhaps this would be better suited to the Shock Brothers or Amp Tech boards, but I'm probably far too new to advise you in this.
     
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  11. JustLetMePlay

    JustLetMePlay TDPRI Member

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    That would be amazing actually, but no stress if you can't. Its not too expensive to get it done here, but as always china has us beat. I've done a few pedals through JLC, they're great.
     
  12. separateness

    separateness TDPRI Member

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    Not sure if this will work but this is a zip file of the tremolo PCB I made in kicad. No luck finding the PCB, so far anyway.
     

    Attached Files:

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