Another Combo Pedal - Well, Sort Of! Cloning the ThorpyFx Heavy Water

The boost pedal market has exploded over the years. I believe part of the reason for the proliferation is some pedals tend to work better with specific amps, many pedals tends to work better with specific guitars, or more importantly specific pick-ups on those guitars. With many guitarists chasing specific or unique sounds, all of these subtle variations come into play. If you've watched any of the Anderton's guitar store videos on YouTube, you've likely encountered Danish Pete - a session guitarist and manager of their YouTube channel. He has a signature pedal called "The Dane" from ThorpyFx that combines a boost and distortion circuit (which would be a good future project...). There had been calls to produce the boost section as a standalone pedal, so ThorpyFx did just that, but took it one better. Instead of just having a single circuit, they created a dual effect pedal, the Heavy Water, which has the clean boost on the right, and a modified "grittier/dirtier" boost on the left. They also created a custom version with dual input/output jacks for people who wanted to create effects loops. I figured this would be a fun one to try since I already knew how to wire up a dual I/O jack pedal where it would function normally just using the input one and output two jacks (my recent Duo-Phase build). So in the final analysis, this is sort of a combo pedal as there are two circuits that can be accessed independently, it's marketed and sold as a single pedal normally.

I unfortunately didn't get any photos of the individual boards before I started fully wiring them up, but I started with two South Obolon FX Deuterium Torpedo boards custom silkscreened for Steggo Studios as the "Atomic Carnivore." Assembly is straightforward and the boards are very well laid out. As the boards are provided individually, you can build a single pedal in a 125B or even the smaller 1590B enclosure, or a dual pedal in a 1590BB. I went ahead and used a 1590BB2 because it provided me more depth to work with. 

I ended up using a mix of resistors for this first build. I was running low on 10M ohm resistors, so I used a 5% carbon film resistor instead of my normal 1% metal film resistors. The rest of the resistors are, however a mix of Yageo and KOA Speer 1% 1/4W metal film resistors, though (with one left-over Vishay Dale thrown in to provide an additional visual differentiation between the "clean" and "dirty" sides so I didn't foul things up in final assembly). The film capacitors are all WIMA and KEMET, and the electrolytic capacitors are Nichicon. There's one OPA2134PA dual op amp on each board, and I've socketed them. Both boards have four 1N4148 diodes. The only real difference between the clean and dirty boards is the clean side uses two 1N747A zener diodes and the dirty side uses germanium diodes. I grabbed a couple of vintage 1N34A diodes I'd picked up from Pedalhacker once upon a time, but I'll likely experiment with others in the future. 

As I'd mentioned before, I followed the same general wiring scheme for the four I/O jacks I used on the earlier Duo-Phase build. This arrangement works very well, and provides a lot of flexibility for dual pedal designs. I'd hoped to ground all four jacks directly to the PCBs, but there is only one additional ground connection on the board itself beyond those needed for power and switching (which would have been find if I was using single I/O). I therefore grounded the outputs to the input, and then the input to the board. Because you essentially have two pedals in one rather small enclosure, the wiring is a bit busy, but I tried to keep the lengths as short as possible.

I'd teased the enclosure art for this build previously on my Instagram page, but the Illustrator files never seem to do the final article justice. I decided to stick with the atomic theme of the original "Heavy Water" pedal name, and found a very cool piece of Spinosaurus clip art to create the Atomic Carnivore. I fleshed out the rest of the enclosure  with some old nuclear patents and symbols. I'd hoped to use some mini chicken-head knobs for this build, but the Low 2 and Boost 1 knobs are just a bit close together to make that work, so I went with some other retro looking knobs instead.

In early tests everything seems to be functioning like the various demos online. The clean side is a nice clean boost, and the "dirty" side adds a fair amount of grit. Things get very interesting when you have both on at the same time - then you're pushing even a solid state amp into distortion territory, and the tone is really crisp without the mud you can get from some dedicated distortion pedals. I'm definitely going to be playing around a lot more with this one!