AxionJFET Preamp

From the vendor

An adaptation of the JFET input stage of the Echoplex EP-3 tape delay unit, famously used by Jimmy Page, Brian May and many others.

The Axion JFET Preamp is based on the Chase Tone Secret Preamp, an adaptation of the input section of the Echoplex tape echo delay from the 1970s.

The Secret Preamp was originally released in 2013 and traced by Aion FX in 2025. We were not the first to trace it, but as an accurate reproduction of the Echoplex preamp, there are no big surprises under the hood. Ours had a few alternate values from other units, but nothing to substantially impact the tone.

This is one of three Aion FX projects based on the Echoplex preamp alongside the Ares (ClinchFX EP-Pre) and Ephemeris (Xotic EP Booster). Each of the circuits takes a different approach to the inexact nature of copying a delay pedal without the delay.

The Xotic EP Booster is a more usable circuit at the expense of accuracy, acting as a more traditional boost with some tone shaping that gets you into Echoplex territory.

The Clinch EP-Pre is a balance of accuracy and usability. The first stage is a direct implementation of the Echoplex, but an output buffer has been added in order to maintain consistent interaction with pedals that come afterward.

The Secret Preamp, on the other hand, is the closest part-for-part recreation of the three, with only the JFET stage and no second boost or buffer. It also runs on a slightly higher 22V internal voltage by reconfiguring the charge pump. (All three circuits still use 9V as a supply voltage.)

The Ares and Axion should sound the same in normal usage. But for those who are concerned about having the closest part-for-part recreation of the Echoplex, the Axion keeps it simple and direct.