The Colorsound Overdriver / Power Boost family went through a few different versions over the years. This layout is for the classic 1971 9V Overdriver version – essentially the 9V successor to the earlier 18V Power Boost, with the same basic three–transistor topology but set up for a standard single-supply pedalboard. It makes a huge, dynamic boost that can run from almost clean to a thick, fuzzy overdrive, with a very effective bass and treble control.
I went with the 1971 9V spec simply because 9V is more convenient, and I had one of the larger Gapco enclosures that suited the longer 0.15" vero format. This layout also includes a post-gain volume control (master volume). Original units did not have this, but given how loud the circuit is, most people prefer to keep the master. If you really want to be vintage-correct you can omit it and wire the output straight from the gain pot.
There is a lot of excellent historical information on the Power Boost / Overdriver on Kit Rae’s site, including a clear explanation of the differences between the 18V Power Boost and the 9V Overdriver, and notes on various reissues.
COLORSOUND 1971 OVERDRIVER – 0.15" VERO LAYOUT
Layout notes: this is a 0.15" stripboard layout sized for a larger vintage-style enclosure. Check transistor pinouts before soldering – the original BC109 devices can be swapped for common modern NPN types if you re-orient the legs correctly. The added volume control is a true output master; if you omit it, take the output directly from the gain pot lug as marked.
COLORSOUND 1971 OVERDRIVER SCHEMATIC
COLORSOUND 1971 OVERDRIVER VIDEO DEMO
Here’s a short demo of this layout in use, showing the range from clean boost through to full overdrive.
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