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Thread: Scrapbox standalone low-voltage reverb

  1. #1
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    Scrapbox standalone low-voltage reverb

    A couple of years ago I had an idea to build a tube reverb without the expense of special transformers. Here in England, tube (more correctly 'valve') transformers are pretty expensive and I wanted to see if something useful could be had from easily-available parts. Here's the schematic exactly as-built. It works very well, though I've yet to sort out switching the reverb on/off. I tried the usual method of grounding the input to the recovery tube, but this introduces too much noise.

    The transformer is a low-cost toroidal - just because that's what I had to hand.

    The TIP35C was used because it just happened to fit the spacing of my tagboard. Only the MOSFET needs heatsinking. The tray I used is from a mid-90's Marshall and I've tried a half dozen different other types and they all worked well. I'm not sure if the circuit will drive a Fender-type low-impedance tray, but the drive from the MOSFET is very strong.

    I know there are lots of design flaws, and room for improvement, but it works much better than you'd expect.

    reverb.jpg

    Here's the final build, apart from finishing the case off;

    reverb.jpg
    J M Fahey, g1, The Dude and 1 others like this.

  2. #2
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    At the bottom there's a diode shorting across the transformer. I think it should be connected to the other side (+ve) of the 4700u capacitor.
    J M Fahey likes this.

  3. #3
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    Well spotted - it's a half-wave voltage doubler.

  4. #4
    Old Timer J M Fahey's Avatar
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    COOL project, congratulations
    Juan Manuel Fahey

  5. #5
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    I like it too. Did you CNC your own faceplate??

  6. #6
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    No CNC - I have an old 60s 'Gravograph' pantograph engraver. I'm not too happy with the lettering - I had the depth of cut set too deep. The material is Traffolite - the original stuff that Hiwatt used.

  7. #7
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    Revised diagram with diode in correct position;

    reverb2.jpg

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