With vintage equipment such as this Eventide delay line, it’s a good idea to check what the manual says about the wiring — it’s not uncommon to find that older devices don’t adhere to the modern AES standard of pin 2 hot. Thankfully, it’s an easy fix!
I have an old Eventide 1745M [a 1970s digital delay line — Ed.] and a Marshall Time Modulator [an analogue delay‑based effects box]. The Eventide is about the same age as the H910 Harmonizer. I can send audio from the Marshall into the Eventide, and I can send the Eventide to the mixer — everything works. But I can’t seem to get audio from the Eventide into the Marshall Time Modulator. There were some strange pin assignments on Eventides in the old days — could that be the problem?
SOS Forum post
SOS Technical Editor Hugh Robjohns replies: Assuming that we’re talking about XLR connectors, the only strangeness is that early Eventide devices were wired pin 3 hot, pin 2 cold (or ground, if unbalanced), and pin 1 screen ground. In fact most US gear before the late ’70s was wired that way, and some UK gear was too. All modern equipment, on the other hand, conforms to the AES standard and that’s the other way around (pin 2 hot, pin 3 cold).
...the simplest solution would be to use polarity inverting (sometimes known as ‘phase reverse’) XLR adaptors — these are not at all expensive.
What this means in practice is that you have a likelihood of unintended signal polarity inversions in balanced connections to modern equipment, and potentially no signal at all with unbalanced connections. I have a feeling the Marshall is unbalanced, and the simplest solution would be to use polarity inverting (sometimes known as ‘phase reverse’) XLR adaptors — these are not at all expensive — or to make up custom cables for the Eventide, with the XLR pins 2/3 swapped over compared with normal modern cables.