The Sigma Vintage Drive is adapted from the Pete Cornish ST-2, traced by Aion FX in 2020.
Cornish pedals are best known for being extremely expensive. There are two reasons for this. First, the build quality and reliability is unmatched. Second, the mysterious nature of them, partially due to the fact that the circuit is obscured and partially because of the A-list of clients such as David Gilmour, Brian May and Pete Townshend.
Pete Cornish originally designed the ST-2 for David Gilmour as part of his custom integrated pedalboard. It was later released as a standalone product in 2007. Other owners include Keith Urban and John Shanks. Lou Reed had one as well.
The ST-2 had long been suspected to be based on the Colorsound Overdriver, given the description, control layout and the first customer (Gilmour is a known enthusiast of the Overdriver). However, it’s never been confirmed.
After tracing it, it’s clear that the ST-2 is definitely based on the Overdriver, but with a few twists. First, it’s double-buffered, the same as the G-2. Second, several values have been changed throughout the circuit and so the overall voicing will be different—it’s not a direct clone. Lastly, an op-amp gain stage has been added to the end to increase the available volume. The original Overdriver could get loud, but the ST-2 can get even louder!
The Sigma is a faithful reproduction of the ST-2 circuit, but with one major addition: an internal slide switch allowing the pedal to be used in true-bypass mode instead of buffered bypass. As with the Klon KTR, the buffered mode is “almost always better”, but with this feature, you can determine for yourself.