ZonkBox Marc II

"Fuzz and Boost in a box, of T Rex fame.  The originals are about as hard to find as a T. Rex today."



The ZonkBox Marc II fuzz rack effect module compares to the super-rare Hornby-Skewes Shatterbox.  It combines a Zonk Machine fuzz with a treble boost and sounds best when they are both used together.  Dirty boogie rhythms or cutting leads are there.  Get it on!



The ZonkBox Marc II is the GT version of the Hornby-Skewes Shatterbox, made popular by Marc Bolan of T. Rex.  The Shatterbox is two separate Hornby-Skewes effects in one enclosure.  The first is a Zonk Machine, often referred to as a Tonebender variant, actually more like a Fuzz Face, but different from both.  The second is a Treble Boost.  Information about the Shatterbox is a bet sketchy, but here's what we've found that we think is accurate.

The first versions of the Zonk Machine and Treble Boost were based on germanium (Ge) transistors.  The second versions used silicon (Si) transistors.  The circuits also changed when the transistor change occurred.  Very few Shatterboxes exist, and the details of their configurations are a little murky.  It is clear that there was a Shatterbox based on the Si transistors with the boost coming after the fuzz, and an earlier one based on Ge transistors where the fuzz came after the boost.  Ours is based on the Si transistors and the second version of the circuit, with the fuzz after the boost.  We offer the Ge version of the Zonk Machine as one of our Fuzzbender configs.

There's some discussion that the Zonk Machines are rather crappy compared to other fuzzes.  Perhaps these comments come from people building or using versions of the circuit that are suspect.  Both the Ge Tonebender-ish version and this Si version we offer sound great, although not alike by any means.

The Zonk Machine uses some large capacitors, which allow a lot of bass through the circuit.  With the Boost off, you get a muffled fuzz sound, unless you are cutting some bass before this effect.  It's a good fuzz sound, but with lots of bass that causes the "there's a blanket over my amp" effect.  But the Boost cuts a large amount of the bass.  When you engage the boost, you get a completely different beast, ready to cut through a band mix easily.  In fact, think of the Boost as the "melt some faces solo time" setting.  It is a bit louder, but mostly it cuts bass and cuts through.

Which did Bolan use?  It's difficult to say.  Some say his tone with the Shatterbox sounds more Si than Ge.  Not many pics show his rig details, although one popular one shows a one-knob Shatterbox, so we can only guess what that one was since it differs from known configs.  He did use Ge Rangemasters, so maybe he had a Ge Zonk and a Rangemaster?  Or maybe kept the Fuzz or Swell pegged and had a custom version built that way?  This module is the Si version, and the Zonk config of our Fuzzbender gives you the Ge version, although you would still need the Ge boost to go with it, such as a Trail Boss

It is easy to imagine Marc playing his boogie rhythms through the Si Zonk Machine and then hitting that Boost switch to cut through for leads.  It seems pretty close to ideal for that.  Originals are nearly impossible to find, and are amongst the most expensive of the vintage effects, costing around $5000.



  • ZonkBox Marc II - compares to Hornby-Skewes Shatterbox, silicon version






  • Bass Cut - Permanently chop down some of the bass to reduce the muffling "blanket over the amp" tone.  It will still have enough bass going through so that when you engage the Boost it will still further reduce the bass to cut through and wreak havoc.
  • Bass Cut Switch - Same as the Bass Cut, but on a switch.  Check availability, as this option is just being added at the time of writing.
  • Carbon Comp Resistors - Get that carbon comp fuzz sound.
  • Boost Order - The original silicon version had the boost after the fuzz, which is the default configuration.  You can switch the order by swapping some cables internally, or we can swap the cables for you.
  • Always On Boost - You can have the boost always on by using the Boost footswitch override control on the back panel.  If you want the Boost to be hardwired as always on, then we can leave off the Boost footswitch.  This allows the module to be 1.5" instead of 2".
  • No Boost - If you just want the silicon Zonk Machine II, we can leave off the Boost completely.  The module will then be 1.5" instead of 2".
  • Custom Components - We use 2N4061 PNP Si transistors by default (same as the original), along with metal film resistors and a selection of capacitors that provide good tone and low noise. 


Front Panel

  • Fuzz
  • Swell (Volume)
  • (optional) Bass Cut switch


Rear Panel

  • Audio In
  • Audio Out
  • On/Off Footswitch
  • On/Off Override
  • DC Power
  • DC Power LED
  • Boost Footswitch
  • Boost Override


Module Width

  • 1.5" standard
  • 2" left wing module and 1.5" right wing modules are available for 2-3 control configurations


Power Consumption (aprox)

12 - 20mA


Base Configurations

Part # Description List Price
MOD-ZONK ZonkBox Marc II module $229



Part # Description List Price
MOPT-ZONK-SWCUT Bass Cut Switch $19
MOPT-ZONK-CCOMP Carbon Comp Resistors $5
MOPT-ZONK-AOBST Always On Boost -$29
MOPT-ZONK-CC Custom Components $0 - TBD



Part # Description List Price
MPT-ZONK-CA Replacement pot, switch, jack, LED cable assembly $19
MPT-ZONK-KNB Replacement control knob $2
MPT-ZONK-PB Replacement power board $29
MPT-ZONK-SB Replacement switching board $29