The Eclipse Boost / Preamp is an adaptation of the preamp section of the Korg SDD-3000 digital delay, famously used by The Edge, Daniel Lanois and William Orbit among others. While the SDD-3000 is a digital delay unit, the preamp (input & output stages) is fully analog, and they would use the unit in bypass mode as a building block for their guitar tones.
The 125B-format update of the Eclipse has a few improvements. First, the attenuation controls have been changed into 3-way toggle switches to perfectly emulate the original unit’s functionality. (On the earlier version of the Eclipse, you’d have to approximate the attenuation level on the knobs, which was inexact.)
Second, the input buffer (which was only engaged in the -30dB position of the original SDD unit) has been added, but made independently switchable so it can be used with any attenuation setting.
Last, while the first version of the Eclipse supported either +/-15V or +/-9V power, the updated version uses a more advanced voltage converter to get a clean and quiet +/-15V from a normal 9V supply. The +/-9V operation has been removed.
The end result is that the build is both more straightforward and more accurate to the original SDD-3000, and now an even-more-exact replica of the original unit’s bypass mode.