The Asteria Preamp Drive Mk. II is an adaptation of the second version of the Catalinbread® Formula No. 5, based on the Fender 5E3 Tweed Deluxe amplifiers from the 1950s. This version of the Formula No. 5 was originally released in 2011 and was traced by Aion FX in 2020.
The Formula No. 5 replicates the quirks of the original Deluxe amp, including a tone control whose effect diminishes as the gain is turned up, with almost no change across the sweep at maximum drive.
Like several other Catalinbread pedals, this circuit blurs the line between a preamp and an overdrive. Like a true preamplifier, it’s very reactive to what comes before it, so it’s best placed after other drive pedals but before modulation. However, it also generates more than enough drive on its own and can be used as a standalone overdrive pedal just like any other.
The two versions of the Formula No. 5 are similar, but still different enough that we decided to release them as separate projects (the Asteria Mk. I replicates the original version). The Formula 55 is a full redesign of the circuit from 2017, and it’s also available from Aion FX as the Asteria Mk. III.
The Formula No. 5 used 2N5457 JFETs, which are no longer available in through-hole format. Extra pads have been provided if you want to use surface-mount JFETs (part number MMBF5457), which are still in production and perform identically to those used in Catalinbread pedals. Aion FX also offers pre-soldered MMBF5457s on adapter boards if you find surface-mount parts intimidating. See project documentation for more information.
The Asteria Mk. II is compatible with the 18V Voltage Doubler / Bypass module if you want to run the circuit at 18V without an external adapter. The higher voltage provides increased volume and clarity.