This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Friday, September 4, 2015

WEM Pep Box

Here's a cool vintage fuzz circuit from the mid 60s–the WEM Pep Box. It's probably best known its use by John Lennon during the Revolver sessions. There are two versions of this effect, the first using germanium transistors and the later using silicon. I've drawn up layouts for both iterations of the circuit, as there are slight variations between the two. The originals used a 500k Level pot with a 56k resistor in parallel. This equates to a 50k pot, so the layouts reflect that. Also, if the effect is to thick for your tastes, try reducing the 2 electro caps down to 10µ. It seems both values were used.

If you're building the germanium version, the layout shows positive ground on the perf side (original transistors were PNP), and the PCB side shows negative ground (for use with NPN germaniums). Since the original ACY41 transistors are pretty scarce now (especially outside the UK), socket and experiment.

Here's a demo of the germanium reissue:


And a demo of an original silicon unit:




6 comments:

  1. ACY41 is UK code for AC128, AC153, AC188. I built one using ACY41 and tested with AC128 it have the same sound.

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    1. Thanks for the info. Did you build the effect using this layout?

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  2. Hi, I'm newby yet, so it can be to easy question but, when I make the fuzz with germanium, is it okay to use AC 128 for both of TR? or, they should be different for them?

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    1. Yes those should work well. Just remember those are PNP transistors, so make sure to use a positive ground power supply, and orient any polarized components like the ones on the perf side of the drawing. Good luck with your build!

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  3. I finally built this pedal with germanium TR AC 128, and it sounds great!
    I recommend germanium for this layout, it is good.
    And I used 7660 for the negative 9V, and it needs only two more line from the original layout. I built this with 1590B case, but it is possible to built this pedal with 1590A also.

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