JOHN HORNBY SKEWES: Shatterbox, 0.15" Vero Layout

Continuing with the Hornby Skewes theme, time for the Shatterbox - original layout below using the old school large format 0.15" stripboard.  Although I'm not sure if I actually want to build one this way...  apart from all the off-board components, it's PNP silicon, which is annoying having a positive earth circuit with none of the benefits of germanium transistors.

HORNBY SKEWES SHATTERBOX - ORIGINAL 0.15" VERO LAYOUT

Photo from freestompboxes for comparative purposes below - a thread can be found here.  Scroll down for the rest of the photos and the schematic on the FSB thread, as it actually starts with someone building one (pinkjimiphoton), not liking it and coming up with an improved design.

The original design has a 100k resistor to ground across the output jack, subsequently affecting all signal through the pedal - so this is not in the true bypass camp as it stands.  It will affect your signal, whether it's on or off.   

I suggest you modernise the switching if you choose to build it, and while you're doing that, you may as well make it NPN and add some LEDs.  Just remember to flip the polarity of the electrolytic caps if you do.

SHATTERBOX VIDEO DEMO

JOHN HORNBY SKEWES: Selectatone TB2 Treble and Bass Booster, Tag Board Layout

While on the JHS thing, I noticed this booster and thought it looked interesting.  The output switches between filters to allow for treble and bass boost, unlike most other boosters where it all happens at the input.

Very few seem to be around, as I could only find one photo of the internals and one video demo.  The schematic still has a couple of assumed (but working) values, which are explained below and marked on the layout.

There's a bit of off-board wiring, which is how the original was built - and no volume control.  

JOHN HORNBY SKEWES SELECTATONE TB2 - TAG BOARD LAYOUT

Image credit: Effects Database https://www.effectsdatabase.com/model/jhs/selectatone#

LTSPICE RESULTS

Both with 100n for the input cap (C1), and the cap linking the treble bass switch (C2).

Changes to the 100n caps (C1, C2) mentioned above have almost no impact on the frequency response of the treble boost (right down to 22n), so tweaking these caps is more around tweaking the bass boost to your liking, and there will be some changes to how it distorts as well.

I split the circuit into two for bass and treble boost, as switches are painful in LTspice - simple SPDT / DPDT switches don't exist.  

For nerdy folks familiar with spice, here's what I was doing (schematic below).   

Short story for lesser nerds, a smaller C5 cap in the bass boost section raises the boost level and shifts it towards the mid-range.  C2 tunes how much low-end roll-off there is.  i.e. you might want a low-mid boost without the flabbiness of too much low-frequency content.

C1 impacts the response, affecting how the transistor distorts, so it's worth trying a 47n in there and a 100n.

Basically, breadboard it and play with C1, C2, and C5. 

Treble boost vs Bass Boost

Input cap variations effect on the Treble Boost output

VIDEO DEMO

OC71 vs 1T308 TRANSISTORS

Spot the difference?  Someone had a question in the comments, so I thought I'd quickly breadboard it for a look - note that this is from the 100n cap on the output, not after the high pass filter.

So turns out they look almost identical, and voltages also measured about the same.   

 

JOHN HORNBY SKEWES: Zonk II, Germanium Version

I started copying the original layout for veroboard and gave up toward the end as it's a cramped mess - this is a similar but more practical version.

The germanium John Hornby Skewes Zonk II is similar to a Fuzz Face but without the 100k feedback resistor, and note that the output cap is taken directly from the collector of Q2, and there's a resistor in series with the cap to take a bit of edge off the output level.  There's also a 680k resistor to help bias the base of Q1, probably due to the missing 100k feedback resistor.

It's a clear departure from the original Zonk Machine, before the silicon model, which also has two transistors.  To make things even more confusing, a hybrid silicon germanium version was thrown in for good measure.

I’ve read that these were made by Sola Sound for JHS in approx 1966-67.    Check the thread on the D*A*M forum for photos, as this is slightly different from one of the schematics.

Also important to note that there were multiple versions, all called the Zonk II, but with very different circuits.  Check out Fuzzboxes.org as a reference to this.

JHS ZONK II - 0.15” VERO LAYOUT

JOHN HORNBY SKEWES: Hybrid Zonk Machine, 0.15" Vero Layout

This is the original layout for the Hornby Skewes Hybrid Zonk Machine (Silicon / Germanium). 

Unfortunately, the trimmer needed to be a different size for the layout, so I had to make a strange triangular marker.

HORNBY SKEWES HYBRID ZONK MACHINE - 0.15" VERO LAYOUT (ORIGINAL)

JOHN HORNBY SKEWES: Zonk Machine (tagboard layout)

The Hornby Skewes Zonk Machine is pretty much a MKI Tone Bender with some value changes - most notably the 1n capacitor on the input and resistors to collectors.

A classic guitar effect from back in the day.

ZONK MACHINE - ORIGINAL TAG BOARD LAYOUT

TAG BOARD LAYOUT

There's enough room on a 12-lug tag board for all the components, so here it is...   probably worth adding an electrolytic from V+ to V- somewhere too.  Just keep in mind that you will need to leave room for mounting screws at either end, so bend around the holes a little.

I didn't include all the wiring - as you can see, there needs to be a few jumpers to connect V- and grounds.  I left them off to make it easier to read, assuming that people can work out what goes where on their own.  

Photos care of effects database.