The Watkins Copicat is a tape-echo machine for musicians that was originally designed way back in 1958. The operating principle is simple: a small loop of tape is continuously fed through a recorder and playback mechanism. That means you can record audio, and immediately play it back — creating an echo. It’s an incredibly popular design, but lacks speed control. On the LOOK MUM NO COMPUTER YouTube channel, they’ve addressed that oversight with the use of a light dimmer switch.
This is a great mod, because it allows the musician to speed up or slow down the recording or playback of the tape. So, instead of getting a simple delayed echo, it can alter the pitch of the effect. That’s a feature on many modern delay/echo equipment, but it wasn’t built into the original Watkins Copicat design — though some versions have it now. That makes sense, considering the design originated in the ’50s and music wasn’t exactly experimental yet, but it’s a useful feature these days.
To make this work, they needed a way to change the speed of the reel motor as it spins the tape. Motor speed control is simple with DC motors, but the Watkins Copicat uses an AC motor connected to mains power. The solution they came up with was to use a light dimmer switch, which is designed specifically for altering the voltage of an AC circuit. By putting the dimmer inline with the hot lead of the Copicat’s motor, the speed can be controlled for some cool effects.