Building a Z.Vex SHO clone from scratch

In my previous post I had some great success building a very simple boost circuit, the Electroharmonix LPB-1. While learning all about that particular circuit I kept coming across discussion surrounding the Z.Vex SHO; mostly questions of tonal comparison. So I decided to build one of those too, and was greatly excited to find this thread, which spelled it all out for me in simple terms. Here’s the circuit in a simple schematic form (I made it in ExpressSCH (on a Linux box)), then a diagram with some options. And finally one with external components that you’d find on a typical pedal schematic:

My own SHO schematic, with bill-of-materials

ZVex SHO “diagram”

Z.Vex SHO schematic

As you can see, it’s very simple. So much so that a fair few forum members decried it as “too simple” and in fact “retarded”. But I admit to wanting to know how Z.Vex can sell one of these circuits in a pedal for more than $150.

Layout

As with the LPB-1 I wanted to attempt a layout myself, and do it on veroboard. This genuinely was quick easy as this really is a simple circuit. My approach as to keep the relative positions of the components on the schematic. It practically wrote itself. It turns out my own layout was wrong, and non-obvious, so I’ve replaced it (on the left) with a decent layout from Mark at Guitar FX Layouts.

Soldering was simple, and went without drama. I was able to test the circuit within the hour. It worked! When I built it I didn’t have all the hardware, so as you can see from the picture, I used a trim-pot rather than a full-size potentiometer.

SHO clone on veroboard

Enclosure

Then the fun part, the enclosure! I’d been wanting to do a decent custom enclosure for quite some time, but never got around to it. This time I decided to make the effort and do something special. First step was to take some good measurements of the enclosure. I had ordered the enclosure from Small Bear, and started by spraying it a lovely fire-engine-red, using Rustoleum paint. That stuff goes on really well and I had no issues with drips or runs.

Decal

Then it came to the decal. I’m not a great designer, or at least not one dripping with amazing ideas for these things, so I looked around at other pedal manufacturers for inspiration. In the end I went for a cheesy tribute to Nigel Tufnel in the spirit of his ‘one louder’ philosophy. With my measurements in hand I used Inkscape to create a set of guides so I would know where all the hardware was going to go on the face of the enclosure. Then I made a simple panel-oriented design that would hopefully go well with the red enclosure. I had deliberately chosen the decal paper that had a white backing to it, so I knew that the upper panel would appear white. I also knew that the gap between them would contain the on/off LED, so that was intentional.

Decal shown in Inkscape

Application

Then it was a case of printing out the design on the water-slide inkjet paper (also purchased from Small Bear). Prior to printing it on the (expensive at $2 per sheet) paper, I did some trial runs on plain paper, just to check for size. You can see in the picture below how the ink looks nice and bold on the real paper compared to the plain paper.

Once printed, I then sprayed a reasonable coat of Rustoleum clear onto the inkjet waterside paper, to seal the ink without letting it run. I was surprised that even after drying for 12 hours the paper was still flexible. Next, I cut out each panel with small, sharp scissors, and made sure it all fit nicely. Finally I soaked each panel in water for about 30 seconds so that the decal was ready to slide off the backing paper. It was simple to apply the decal to the enclosure and get it lined up with the edge. It was most pleasing that my measurements were good, and also that the printer was accurate enough to obey my measurements. After smoothing out the decal with a bit of tissue I left it to dry overnight.

Decal ready to be applied

Finish

The next day I got things setup to shoot some clearcoats onto the enclosure. I planned on applying 5-6 coats, or until I got bored. This proved easy as long as I kept within the one hour time limit. If I waited longer than that I’d have to wait a further 23 hours to apply another coat.

Assembly

Well, it’s all assembled, and it is fully functional, but I’m not magically happy with the finish. It looks great, but it’s really really soft. It dents easily, even with cloth and finger prints. Maybe this means it will hold up really well to abuse because it won’t chip? Time will tell.

I am however pleased with the LED lenses, which I got from Mouser. Fulltone use a fresnel-type lens on their pedals, which I liked immediately. And to be honest I’m tired of the standard ‘chrome plated cone’ type that I’ve been using up until now. These ones are made by VCC and available from Mouser…try part 593-3210C (tall, like on this booster) or 593-2800C (flatter)

The finished article

The 3PDT wiring

Starting with the left column, top to bottom:
Output from circuit, output to jack, link to input (bypass).

Middle row:
9V power from DC jack, wire to LED load resistor, nothing.

Right column:
Input to circuit, input from jack, link to output (bypass).