Pages

▼

Saturday, 22 January 2011

Gary Hurst Tonebender MKI

 

Like the last one, a bit of a pain but the Gary Hurst version is slightly more forgiving I believe.  Again don't forget to cut the trimmer legs that are shown over the -9V rail, there should be no connection there.  This is based on the original Gary Hurst MkI because the reissue was in reality a MkII.  Maybe Gary thought the MkI's are a pain as well! :o)

This one is verified

 



Updated 31st January 2014:  A lot of people have mentioned that the trimmers in this aren't as important as finding the correct transistors, so I'd recommend building this version which omits the trimmers entirely and puts the fixed resistors back.

Make sure you use sockets for the transistors and prepare yourself to audition plenty! :o)



at

22 comments:

  1. dwstanford6 February 2011 at 21:09

    I am looking for a decent transistor set for this build. I contacted Steve at Small Bear Electronics and he said that the tonebender MKII sets that he sells will also work for the MKI. Would that be a good idea?

    ReplyDelete
  2. IvIark7 February 2011 at 21:05

    Yes they'd be perfect

    ReplyDelete
    Replies
    1. finom130 March 2013 at 13:51

      Hi,
      I would like to build this pedal. Do you have a wiring diagram? I am not used to this type of layout.
      Thank you,
      finom1@gmail.com

      Delete
  3. dwstanford14 February 2011 at 19:45

    I just got the components for this one in. I will let you knowhow it turns out.

    ReplyDelete
  4. IvIark15 February 2011 at 00:23

    Cool, I'll be interested to hear how it turns out.

    ReplyDelete
  5. Unknown15 September 2011 at 18:25

    What kinda pots for the MKIs? Linear or Audio?

    ReplyDelete
  6. IvIark15 September 2011 at 20:32

    I used linear for both

    ReplyDelete
  7. mirosol12 July 2012 at 06:43

    I think i want to try this with those russian NPN germs.. Seems to me like it should work if electrolytics and 9V/gnd are just reversed...
    +m

    ReplyDelete
  8. Dom1 September 2012 at 01:54

    What kind of trimmers are those? Thanks.

    ReplyDelete
    Replies
    1. IvIark1 September 2012 at 02:20

      They are Spectrol 20K 10% Square 10mm Single-Turn which I got a few of cheap on eBay. It's a pain trying to get side access to them though so I'd suggest getting this type instead:

      http://www.ebay.co.uk/itm/290765369870

      They're multiturn but that gives you so much resolution to bias things just right for you, and the top screw adjustment is much better. I'd suggest getting it to the right sort of resistance between the appropriate pins first though, it would make things much easier and quicker to fine tune once installed.

      As an added bonus they only take up 1 column instead of 2 so you could potentially save a bit of space too.

      Delete
  9. Unknown30 September 2012 at 14:31

    I could do with a bit of help here! I built this up this morning, and have been trying to bias it.. while doing that, I noticed that the voltages were a bit odd (in my mind, could be completely wrong here). I got it to a point where the effect is working ok, it gates but I believe that is part of the MKI charm. Here are the voltages..

    Q1 C 9.67
    B 0.36
    E 0.40
    Q2 C 7.75
    B 0.13
    E 0.00
    Q3 C 9.46
    B 0.00
    E 0.00

    The values of the trim pots are set at 9.7k for Q1 and 800R for Q3. If I increase the trimmer for Q3 anything above 800R, there is a squeal in the note decay. It doesn't seem to matter where the trimmer for Q1 is set, as long as the trimmer for Q3 is set low - just before noise is introduced to the circuit. I can set the trimmers up the opposite way, with the same results (Q1 800R, Q3 9.7k).

    I have tried various transistors, and various hfe values. I have some OC75's all within the range of 60-70 hfe, some MP16B's within the range of 60-110hfe. I was shooting for Q1 65hfe, Q2 95hfe and Q3 90hfe - as per the discussion on FSB about this circuit. I was careful to select transistors with leakage of about 200ish except Q3 (75ish).

    It sounds ok, don't get me wrong.. but something seems a bit strange with both the voltages and the values I ended up with on the trim pots. Can anyone share their voltages, or whatever? Thanks in advance. Danny

    ReplyDelete
  10. souljah23 September 2013 at 14:46

    this is a pain in the arse circuit, i am having trouble getting mine biased correctly as others have mentioned it sounds good but it just gates very strangely, i built this in a box with a mkII as well and to be honest i dont think i will use the mkI side much

    ReplyDelete
  11. G.G.20 February 2014 at 15:04

    I've built 2 MK1's using this layout (works great, and thanks for the layout!). One used a generic matched set of Small Bear's PNPs and the 2nd a set of SB's OC75's. They both sound quite good but compared with other pedals they just don't seem as loud, even with the volume at max. Is that typical of this circuit or should I be looking at something in my build?

    ReplyDelete
    Replies
    1. superferrite19 April 2017 at 21:32

      Had the same problem. Replaced the 2M2 resistor at the end with a 1M and it worked great!

      Delete
  12. Jimijam26 May 2014 at 23:18

    I was trying out this and I get a screeching mess when you start turning the attack pot, solved it by putting a 4.7nf cap to ground on the input -
    I have used a ton of transistors too. Any thoughts on this?

    ReplyDelete
  13. G.G.3 June 2014 at 23:12

    Hey gang, here a demo clip I made of my build. I used a set of OC75's from Small Bear. Thanks for a great layout!
    http://youtu.be/sygN8KiBiTY

    sorry for the double post, I thought I accidentally replied to the wrong thread.

    ReplyDelete
    Replies
    1. IvIark3 June 2014 at 23:36

      Excellent stuff, thanks for sharing the clip.

      Delete
    2. Jimijam11 June 2014 at 01:25

      Woa! Finally... sad to say but after almost a year... GOT THIS!
      Yeah this circuit is a royal pain to tinker with but I ended up using a super low leakage Russian transistor for Q1 and a couple of OC75s for Q2 and Q3 and this thing is by far my favorite Fuzz pedal now... I am going to super glue it to my pedal board...
      Boxing it up and DONE! :-D

      Delete
  14. Ian G10 November 2014 at 19:07

    build it with some AC128's I got from TBmk2 build - it sounds really nice... the attack knob does almost nothing - goes from none to full blast between 9 and 10 o'clock and then its the same. I think I'm gonna change the attack pot to a regular resistor and keep it as a one knob fuzz just because I like the way it sounds.
    http://youtu.be/cHK81RJIkdw here is a bit of testing it.

    ReplyDelete
  15. fuzzbender8 January 2016 at 04:06

    I'm having some trouble with a Mk.I build, as well. What are the correct voltages for this circuit? I used all the stock values in mine and it's muddy sounding and gates pretty badly. There's also a sizzling noise in it as the notes decay.

    ReplyDelete
  16. Unknown15 March 2016 at 22:10

    Is this the original prototype MKI tonebender? If so where is toggle switch?

    ReplyDelete
  17. superferrite11 April 2017 at 06:32

    After approximately FIFTY successful builds, I finally cobbled this one together, figuring my stash of two or three dozen PNP germs HAD to have a magic set in there somewhere.
    Fired up with just a couple of swaps! Sounds groovy, man! Can't wait to dial it in and start melting faces!

    ReplyDelete