Monday, 1 May 2017

Hornby Skewes Zonk Machine II

Best info I could find on this creamy classic fuzz goodie.

The 1967 John Hornby Skewes Zonk Machine II is an extremely rare, and vintage pedal enthusiasts have long coveted both the original Zonk and its successor, the Zonk II. The Zonk II was the result of a re-engineered Zonk Machine I, which was based upon the Sola Sound MK I Tone Bender circuit. Featuring (2) PNP M2N 4403 Silicon transistors, instead of the earlier (3) Germanium transistor based Zonk Machine I, the Zonk Machine II is more stable, smoother, and less dark sounding. Effectively designed to be a complete and practical unit, the Zonk II’s predecessor was intended to be used in conjunction with the JHS Treble Booster unit (essentially like a Rangemaster) as to enhance the articulation and clarity of the otherwise muddy Zonk. Interestingly, John Hornby Skewes did offer both units within one box, and it was re-branded as the famous Shatterbox.



The rolled steel casing with a blue Hammerite finish is very reminiscent in design to the gold MK I Tone Bender: with two basic controls on top, and the input and output next to one another on the back, the straight-forward aesthetic is a reflection of the absolute perfect simplicity of the circuit within. It is loud, robust, full-range, and complementary with most any rig. It is sweet, subtle, and sings with sustain. Completely inspirational to play through, the Zonk II offers endless enjoyment, and tone otherwise unavailable via a reissue, clone, or kit.





Layout 1: Original PNP



Layout 2: Original NPN



26 comments:

  1. So, One of these is + ground and one is - ground? So, that means you can't power daisy chain layout 1, right?

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    1. the original was positive ground (PNP), which you would not be able to daisy chain with negative ground (NPN) devices. you can build the NPN layout and daisy chain it without issues.

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    2. Thanks Zach, that is what I figured. I was just making sure (I'm still learning a lot of this stuff....)

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    3. no worries todd. never hesitate to ask questions. it's the only way to really learn things.

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  2. Right. #1 is a PNP transistor design.

    If I have this figured out right that means it uses a -9v power source versus the +9v source of the NPN design. It's whatever the circuit is designed to draw from the power supply. In the case of the design with the PNP transistors it draws -9v. In the NPN design it draws +9v.

    That's why you can't daisy chain it (the PNP design) with other pedals that are NPN type designs.

    The idea behind positive ground or negative ground is actually confusing or not quite right. It's my understanding that ground is actually 0 volts. Neither positive or negative.

    Some pedals actually use a bipolar power source. They have two power rails, one +9v, the other -9v, and again ground is 0v. That's why "positive" or "negative" ground is confusing it should be positive or negative "power". Either way you cant daisy chain pedals with different power polarity requirements.

    Either use batteries, a charge pump/power inverter, or it's own dedicated power supply.

    It's a pain in the A**, but it is what it is.

    Hope I didn't confuse you further, instead I hope I helped. I give credit to this wonderful web site and all the people involved for what I know now. The amazing thing is what a bargain it is! LOL.

    Will

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  3. Hah, LOL.
    Figures. I took to long answering.
    Well, Zach is certainly the authority.

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    1. haha will. i figured i would just give the shortest and quickest answer.

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  4. Ha, you got me right. If there's a way to make it longer, more drawn out, & more complicated I will find it. LOL

    Still, I have to say; 3 years ago I knew nothing about FX pedals, & electronics beyond protons, electrons, & electromagnetic theory. I have this wonderful place & the people in it to thank for all I've learned, the many FX pedals I've built and I use every day. It's priceless, and so again:
    Thank you very much, IvIark, Zach, Alex, Mirosol. I know there are others, many others. FSB & DIYSB too!

    Good luck Todd, with your build, and the countless others you will build & enjoy because of this little blog . . . .

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  5. caught and error in the layouts. there's 4 cuts not 3. i made the correction to the layouts.

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  6. Where's a schematic for this two transistor version?

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    1. honestly i don't remember cause i've had it for awhile. probably FSB or DIYSB.

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    2. It's on FSB. I'd post it but I'm not sure if that's proper. Just search FSB, It will come right up.

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  7. Ahem, My apologies.
    The schems I found there are all 3 transistor versions.
    This is the link:
    http://www.freestompboxes.org/viewtopic.php?f=19&t=16723&hilit=Hornby+Skewes+Zonk+Machine+II+Search%E2%80%A6

    D*A*M* had some killer images on their forum. You could certainly trace a new schematic from those, link:
    http://stompboxes.co.uk/forum/viewtopic.php?f=6&t=1045&hilit=shatterbox+zonk+ii

    I'm still looking for it. If I find it I will post the link.

    Will

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    Replies
    1. Fuzz Central Has it. Look under Schematics & PCB's.
      Will

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    2. Found another 2 (on the D*A*M forum this time):
      http://stompboxes.co.uk/forum/viewtopic.php?f=6&t=8081&start=40
      I guess that s/b enough? LOL.
      Will

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    3. the schematic i used looks like the one from fuzz central. i also tweaked the layouts to match the sola sound schematics from the dam forum that you posted the link to, and made a new post with them. cheers on the find. can never have enough classic germanium fuzzes.

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  8. Thank you so much, Zach. Never enough good Fuzz' to mess around with, looking for that magic, elusive tone. Plus all that I get to learn in the process.

    Wow! just checked the new post. You just gave me my 15 minutes of Fame! LOL!

    I think I'll print it, frame it, and hang it on the wall in front of my workbench . . .

    You just made my month, Zach!
    Many thanks.

    Will

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    Replies
    1. cheers man. got to give credit when credit is due. i didn't even know those existed, so i wouldn't have been able to do the layouts if you didn't find the schematics.

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  9. i made this, the NPN version. it sounds great... or at least it would, but it is SUPER, unusably muddy. i used 2n2222a and all carbon comps. even dug up old caps for everything. i thought it might be the caps being super high so i swapped them out for 2uf input, 33n output and 10uf fuzz 2 to ground, and it sounded the exact same. i even swapped transistors, and put the 3.9k resistor on a mini toggle. nothing is changing. help?

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  10. I tried the NPN version too, tried several transistors - 2N2222, 2N3904, BC550, couldn't get it to work, at best I can get a very faint signal with literally everything cranked up (source, desk, etc.)

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  11. Pretty sure Swell 2 and Swell 3 should be reversed, as this is the same as volume controls on all other similar circuits.

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    Replies
    1. nope, not according to any of the multiple schematics for the zonk. the swell control is exactly as it's indicated in the layout.

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  12. So has anyone verified this yet?

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  13. I built the PNP but something isn't quite right. Gain seems to work although I get some odd artifacts when stopping a note on max. The swell also "works" but I have almost full volume, less saturation when all the way off. Maybe this is how this circuit works?

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