AionFx Sigma (Cornish ST-2 (Colorsound Overdriver))

[apierz]

Build Rating

4.00 star(s)

My main overdrive sound is the green side of a Protein, and then using the blue side if I want a louder, more open tone or using a Kliche in front of it for a more compressed, fatter sound. I haven't built a pedal in a while so I figured I'd audition some new builds to see if anything tops the Kliche. I've mostly been looking at lightly dirty boosts that sound good on their own to add volume and compression without adding in too much grit . I've been playing it for a few days now and it's growing on me. With the gain maxed it gets a little splatty but when dialed in I dig it, especially as a boost into another overdrive. I'm going to keep it on the board for now (other contenders yet to be built are the Blue Yonder and Fumble Boost).

Build-wise, this is a pretty packed pcb with all the weird part values you would expect in a Cornish clone so I got to see a whole bunch of resistor band colors for the first time. It doesn't show in the gutshot very well, but it is pretty colorful in there. Also I got some too-big electrolytic caps for the main filters but they ended up just barely fitting. I give the build out of five, mostly because the lack of ground pads at the top of the PCBs on @aion pedals. Having to wire all the grounds together and get it in the power jack always gives me fits. I think I have a better strategy for the next one, but every time I do an Aion build I am reminded how glad I am @Robert adds those ground spots in. I hate internal switches so I hardwired it for the buffer to be always on.

This is also my first time doing any kind of design on a pedal, and thanks to @Fingolfen 's helpful UV printing tutorial I was able to figure out how to get a successful PDF design starting in Inkscape and importing/finishing in Affinity designer. I've always liked the way Cornish does his gray box pedals in a so ugly it wraps around to being beautiful way, so I tried to ape him as best I could. I'm happy with the level of detail and accuracy Tayda can do and, now that I know I can get it right, I've got some more complicated designs for the next ones.

Here's an audio sample with a telecaster bridge pickup that will probably be in no way relavant to your guitar/rig. First its clean, then Sigma engaged with guitar volume at 7, then guitar volume at 10, and then the green side of the Protein engaged too.

 

[MattG]

Have you by chance compared this to a stock Colorsound Powerboost or Overdriver? The ST-2 definitely has that in its DNA, but has some tweaks.

I built several Colorsound PB/OD pedals over the years. One thing they were “famous” for is the splatty decay when used as a light overdrive or dirty boost. The Boss BD-2 does this too, but IME it’s more overt in the Colorsound circuit.

They were also capable of crazy volume, so I find it odd Cornish felt the need to graft that TL071 gain stage to the end of the circuit.

Can the Sigma/ST-2 do all out fuzz with the gain maxed out? From reading other discussion forums about it, I got the impression it’s more clean boost/EQ than overdrive or fuzz.

As you can probably tell, I’ve always been curious about this circuit!

That’s a fantastic looking build and a great report, thanks for sharing!

 

[apierz]

After playing it for a while at a bunch of different settings, it seems like Cornish wanted to make the pedal cleaner than the original Overdriver. I haven't tried a true Overdriver or direct circuit clone, but the demos of the Overdriver I have seen show it having more clipping than the ST-2. Even at max gain it doesn't get too fuzzy until the notes start to trail off, though its more pronounced with low end notes. Putting a boost in front of the Sigma with the gain knob maxed will put it into fuzz territory.

For me, there was basically no difference between my clean tone and the pedal with the gain around 2 o'clock, and the other knobs at noon to 1. The clipping and fuzzy decay starts with the gain around 3 o'clock.