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Tuesday, 7 February 2017

WEM Pepbox

   This was requested in the forum. There is a photo of the Beatles where you can see this pedal, so it should be a fun build for us Beatles fans!


   Here's the Ge version first:



   
Then the Si version:



And finally the Si version with the tone control mod like the Ghost Effects kit:




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29 comments:

  1. neal gardner7 February 2017 at 07:04

    Suitable alternatives to a BC107... 2N3904 (max hfe 300)? BC547B Max hfe 450)? Suggestions? Thanks!

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    1. Claudio7 February 2017 at 12:37

      BC107 is hfe 110, so a replacemente could be 2N3904, 2N2222A, 2N2369A (same TO18 enclosure), NTE123A. I will go for no more than 200 hFE



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    2. neal gardner8 February 2017 at 05:02

      Much appreciated!

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  2. Thorsten7 February 2017 at 18:11

    For those that want a sound demo:

    https://www.youtube.com/watch?v=SmIlo0DVA1o

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    1. Travis8 February 2017 at 01:20

      That's not a Pepbox though, it's a "British Pedal Company" pedal. Those guys have really great looking enclosures and crap sounding builds. They are a joke among vintage pedal enthusiasts

      In that video I hear a really badass amp and a pretty lame fuzz. If their other pedals are anything to judge by, this should sound a lot cooler if you put some effort into the sound rather than marketing bullshit.

      Don't mean to rant but BPC sucks big time.

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    2. Thorsten9 February 2017 at 13:26

      In that case you are free to delete my YT link if it does not reflect the build here :) Just meant to help those that have no clue what to expect from the build, like myself.

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  3. Jacob7 February 2017 at 23:00

    Interesting, have you seen this 3 transistor version?

    http://musical-den.blogspot.com/2008/07/more-on-that-pepe-rush-fuzz.html

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  4. Travis8 February 2017 at 00:32

    Thanks Jacob! I wasn't aware of that version. It is almost a verbatim FZ-1 clone. It looks like the values that were changed were just the closest values that Pepe had on hand, which are within 10% tolerance of the original FZ-1 resistor values. The 20uf coupling caps were changed to 1uf which probably won't have an audible difference. All in all I bet it sounds pretty much identical to an FZ-1 but I will draw a layout for it if you like. If not just take the existing FZ-1 layout and change a couple values

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    1. Jacob8 February 2017 at 13:52

      Thanks Travis! I thought the same thing when I looked at it in regards to it being a FZ-1 clone. I just wanted to mention it for posterity's sake. No need to waste your time on another layout when using the FZ-1 will work. Thanks for all you do!

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    2. EddieB8 February 2017 at 18:12

      The 3 transistor version is remarkably similar to the Gary Hurst Mk I Tonebender, which of course was basically an FZ-1 clone. Also the Hornby Skewes Zonk Machine.

      BTW, I've been working on a Mk I Tonebender derivative that is actually buildable by mere mortals without requiring germanium transistors that have blessed by the gods. I intend to post it to the forum in the near future.

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  5. hobbystubba8 February 2017 at 07:10

    Thanks Travis, sounds mean. love it.

    Shoved 2 unmeasured MP16Bs in and it lit the place up straight away :D. Easiest ge build yet

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  6. Travis8 February 2017 at 14:08

    Awesome hobbystubba! Thanks for letting us know

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  7. Claudio9 February 2017 at 22:01

    Well, I tried the silicon scheme, with different transistors, since I don't have 1M trimmer I used 2.2M and adjust to 820K for first try.
    2N2369A 60 hfe, sucks really farting sound even biasing, If you go to low with trimmer you could start fire like me ( I guess I fried bot 2369A)
    BC550C 300 hfe good sound without bass and body, too trebly to my ears.
    2SD30 Ge NPN Transistors 100 Hfe, good sound, more body and more bass, biasing is more easy.
    Even though I changed to 500K trimmer I couldn't find a sweet spot for biasing, and be careful you can get smoke if you go to low, I will try with 100K trimmer, or try Ge version scheme but with NPN.
    Someone can put some light to the trimmer problem?

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  8. Travis10 February 2017 at 02:33

    If the BC550C sounds good but lacks bass I would just bump up the 3n3 output cap. Alot of 60s pedals can be pretty bright.

    It's kinda not surprising that the trimmer would do that, I wonder if that's an error in the trace or just a weird design? Basically at a certain setting it will come within 100 ohms of shorting 9V and ground

    The fuzz pot will affect the bias of q2 in the Ge version, then the si version has the fuzz pot no longer affecting the bias, but the goofy voltage divider trimmer

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    1. Claudio10 February 2017 at 12:16

      I made a modification for a tone pot, like ghost re-edition http://www.ghosteffects.co.uk/pdf/si_pep_box_pcb_guide.pdf
      Sounds good and very useful.
      My first try was trimmer at 820K, and voltage was 9.02, on 500k trimmer was the same, I went from 9 or 8 volts to zero, I will try with 100K and rotate very very slow

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    2. Strewel Peterson12 February 2017 at 18:51

      I've blown up transistors whilst twiddling the trimmer on this too - I think the reason is that you can set a full 9v across the base-emitter junction. The datasheets I've checked give absolute max values of 5-7v here. Maybe put a fixed resistor in series with the trimmer so that max bias voltage can't go above, say 5v. Something about the same value as the effect pot ought to do it? Mind you, maybe the magic sound comes just before the incineration point?

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    3. Strewel Peterson12 February 2017 at 18:53

      ...or maybe, in the case of my playing, just after the incineration point, when silence reigns once more.

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    4. Claudio13 February 2017 at 12:23

      is a good idea, maybe put a 10K in series to limit the trimmer, I'll give a try

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  9. Anonymous14 February 2017 at 11:29

    I built the germanium version using NPN Russian germs and it sounds pretty good. So it's verified for NPN germ if you reverse the caps! I might add a tone pot though as it is quite bright.

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  10. Unknown17 February 2017 at 16:10

    I built the BC107 version and it works great. I used a 500K trimmer and incinerated a few trannies but I found that with a hfe of 411 they didn't fry but hfe 440 upwards did. It needs a tone pot though!

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  11. Travis17 February 2017 at 20:37

    Thanks to the three that verified it and shared build info!

    I'll update the silicon version to call the trimmer 500K and add a warning not to turn the trimmer all the way up or down.

    I will also add one with a tone control like Ghost Effects is doing (they basically used the tone control from the MKIII Tone Bender). If you don't need a tone control but want more bass, just increase value of the 3n3 output cap

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  12. BigZed18 February 2017 at 09:22

    Thanks Travis, a tone control would make this a great build for me!

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  13. BigZed18 February 2017 at 12:57

    I've used BC107's with hfe around 220 each and added a tone control...this build is really a worthwhile project, different from the normal fuzz's I really like it. So well done Travis, awesome!

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  14. Anonymous22 May 2017 at 11:39

    Just built the 3rd option here - the silicon version with tone control. I used 2N2222As hfe around 260-ish, and swapped the output cap for an 18nF cap. I just picked a random value larger than 3n3! Also used a 1M trimpot as I didn't have a 500K and it's pretty obvious when you get the bias right. It stops gating. There is a very narrow range where it seems just right.

    Anyway it is a lot more useful than the germanium version I first built. I love the tone control. I may still experiment with the output cap but 18nF sounds full but not too flabby. Thanks for the layout - it's a good one. Good range - and usable range - of dirt.

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  15. neal gardner27 June 2018 at 02:07

    I recently found a pristine batch of old RCA 39393N's at a junkyard. I popped them in, adjusted the trimmer, and yeah, it sounded nice. Check it out.
    https://www.instagram.com/p/BkdWlyvlYqm/

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  16. SlimShitman23 December 2020 at 17:39

    Hey! Built the GE Version using ACY20s. On its own its super quiet and only clipping slightly but with a pre sounds ace. Can anyone tell me, is the quietness my transistor choice? Thanks for the layout!

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  17. S. 23 September 2021 at 16:19

    I’m building the third one today. What voltages should I aim to get for both transistors?

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  18. Pete14 December 2021 at 00:08

    Any idea what the readings should be on the transistors

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