The Thagomizer 2 - A Cornish ST-2 Clone

So as promised in my recent Thagomizer I update, there is indeed a Thagomizer 2, and I'm presenting the prototype build today. The Thagomizer I is a cone of the Colorsound Power Boost - at this point built with all vintage components. The Power Boost is very closely related to the Colorsound Overdriver, which I'd also previously built - though with all modern components. I first became interested in both of these pedals when researching David Gilmour's effects boards. In later years, however, David worked with Pete Cornish to develop a custom integrated pedalboard - which Pete later released as distinct effects pedals in their own right. The ST-2 is a major overhaul of the original Overdriver circuit with different component values (and therefore different voicing), a double buffer like the G-2, and an op amp gain stage tacked on to the end of the circuit. With new copies running over $500 (with a long wait) and used copies starting at about $650 - this is yet another pedal that screams for a good clone!

For this build I started with the AionFX Sigma board, and as evidenced in the photo above, this is yet another very densely packed board. For comparison, I've included a picture of the board from the AionFX Plasma clone of the Colorsound Overdriver below. As is typical for a Cornish pedal, the ST-2 is incredibly complex with a very high parts count - and in addition to the high parts count, many of the parts (especially the resistors) are in unusual values. In fact, there are almost half as many resistors with a value of 100 Ohms or less in the ST-2 (a total of seven) as there are resistors of any value in the entire Overdriver build (15 not including the added RPD and LED resistors). 

As is typical for my builds with modern components, I generally used the high-end component recommendations from AionFX purchased from Mouser. Where the recommended part was out of stock, I found something equivalent or better. The resistors are all Yageo or KOA Speer 1% tolerance. The film capacitors are all WIMA or KEMET. The electrolytic capacitors (and there is an army of them in this build) are all Nichicon. The IC is a TI TL071 in a high-end round hole socket.

As with all of my new builds, this one has the production code, serial number, and Steggo's signature on both halves of the enclosure. Because the black enclosure paint carried over into the inside of the enclosure, I used my chrome pens to add the vitals on the main part of the enclosure.

I'm trying to keep all of my wiring a bit cleaner these days, so I'm using more ribbon cable to connect the 3PDT daughter boards to the main board, and all of my hook-up wiring I'm trying to set at fixed lengths. All of the jack connections (input, output, and DC) are shrink wrapped. Since this is my personal prototype, I ended up re-using a couple of jacks that I'd mis-soldered in previous builds. This not only brings my prototyping costs down, but helps me get better at de-soldering components as well!

The enclosure is once again an homage to Pete Cornish's enclosures, but I had the foresight not to simply copy the ST-2 name. This is, of course, the TH-2 for "Thagomizer 2." I'll likely end up building more of these, but they'll have different artwork going forward. Hopefully something that's a bit more uniquely "Steggo" - though it is helpful for me to have my personal pedals in something close to original livery so I can keep them straight at a glance without having to refer back to all of my documentation!

I tested the pedal's sound last night practicing with my MIM Stratocaster, and honestly I'm extremely impressed. I expected it to be a bit louder than it was, but it's still plenty loud when compared to my Overdriver clone. It is also more of a boost pedal as even at higher gain settings you don't get some of the distortion that you get with the Overdriver at high gain settings. The video above using an original pedal sort of gives you the feel of what it can do. In short, in a lot of ways it feels like the clean side of my Power Boost clones, which is why I decided to call it a "Thagomizer" rather than something else.