One Falcon Heavy Drive prototype was built and gigged before the first run of Falcons. It had three JFET stages (the third was only available on channel two) and some different mid notch and clipping options.
A bass-specific version was breadboarded but ultimately folded into the main Falcon Heavy design.
The original naming, seen in the videos below, was “Falcon Drive” for the guitar version and “Falcon Heavy Drive” for the bass version; the combination of these designs resulted in the production Falcon Heavy Drive.
This Falcon Heavy Drive prototype had a different mid notch than production Falcons. The clipping modes were no diodes, asymmetric MOSFET clipping, and asymmetric Schottky diode hard clipping.
The breadboarded bass Falcon had the same mid notch as production Falcons, with no diode, symmetric hard-clipping silicon diode, and asymmetric Schottky diode clipping modes.