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
So, One of these is + ground and one is - ground? So, that means you can't power daisy chain layout 1, right?
ReplyDeletethe 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.
DeleteThanks Zach, that is what I figured. I was just making sure (I'm still learning a lot of this stuff....)
Deleteno worries todd. never hesitate to ask questions. it's the only way to really learn things.
DeleteRight. #1 is a PNP transistor design.
ReplyDeleteIf 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
Hah, LOL.
ReplyDeleteFigures. I took to long answering.
Well, Zach is certainly the authority.
haha will. i figured i would just give the shortest and quickest answer.
DeleteThanks Will :)
ReplyDeleteHa, you got me right. If there's a way to make it longer, more drawn out, & more complicated I will find it. LOL
ReplyDeleteStill, 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 . . . .
caught and error in the layouts. there's 4 cuts not 3. i made the correction to the layouts.
ReplyDeleteWhere's a schematic for this two transistor version?
ReplyDeletehonestly i don't remember cause i've had it for awhile. probably FSB or DIYSB.
DeleteIt's on FSB. I'd post it but I'm not sure if that's proper. Just search FSB, It will come right up.
DeleteThis comment has been removed by the author.
DeleteAhem, My apologies.
ReplyDeleteThe 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
Fuzz Central Has it. Look under Schematics & PCB's.
DeleteWill
Found another 2 (on the D*A*M forum this time):
Deletehttp://stompboxes.co.uk/forum/viewtopic.php?f=6&t=8081&start=40
I guess that s/b enough? LOL.
Will
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.
DeleteThank 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.
ReplyDeleteWow! 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
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.
Deletei 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?
ReplyDeleteI 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.)
ReplyDeletePretty sure Swell 2 and Swell 3 should be reversed, as this is the same as volume controls on all other similar circuits.
ReplyDeletenope, not according to any of the multiple schematics for the zonk. the swell control is exactly as it's indicated in the layout.
DeleteWoah.
ReplyDeleteSo has anyone verified this yet?
ReplyDeleteI 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?
ReplyDeleteSame problem here. I built NPN version and also get horrible noises when not playing with gain on max . With gain rolled down it is kind of fine.
DeleteI built NPN version, I used BC108B transistors and this sounds amazing! Doyle Bramhall's secret weapon tones!
ReplyDeletenpn bc107 200hfe
ReplyDeleteHey Zach. I recently acquired a vintage Hornby Skewes "Transistor Mixer Unit" that's been modified beyond original functionality. I'd really like to restore it to its original condition; any chance you'd be able to help with the schematics?
ReplyDeletehey man. i don't have a schematic for that one and did a search, but didn't come across a schematic for it.
DeleteI built this and it is muddy, but like the Zonk I I think that's just the way it goes -- sounds much better with a boost (like LPB) in front (as do most zonks and mk i's in my opinion). Does make some noise when swell is maxed, but backed off just a tiny bit the noise goes away. Worth building given how simple it is. I tried bc107s and bc108s and preferred the nastier and wilder tone from the 108s.
ReplyDeleteVery farty.... I tried changing input and output caps, not much love. I used 2n5089s because with 3904s there wasn't enough output. I ended up throwing a clean full spectrum boost in front... perhaps I should have tried a treble boost but honestly this circuit was a bomb for me...
ReplyDeleteAnyone have transistor voltages for this? Or know of a post that lists em? IV searched many threads and can't find em, so any help would be appreciated. I built the one version and it sounds ok, but a little mis-biased.
ReplyDelete