The Asteria Preamp Drive Mk. I is an adaptation of the first version of the Catalinbread® Formula No. 5, based on the Fender 5E3 Tweed Deluxe amplifiers from the 1950s. It was originally released in 2010.
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. The Aion FX version adds a toggle switch to increase the gain of the first stage.
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 Formula No. 5 was updated in 2011. The second version is very similar, but still different enough that we decided to release it as a separate project called the Asteria Mk. II. The Formula 55 was the third update, releasing in 2017, this time a near-complete redesign. The Formula 55 is also available from Aion FX as the Asteria Mk. III.
The original 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 details.
The Asteria Mk. I 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.