I'm using an external spring reverb in my Scope mixer. It's great, warm and "analog"
but, as it is not very versatile....Scope offers the tools to control it and "transform it, I used the modular to do it, but recently I made this device that does the job pretty well.
Try to imagine your long sprimg or your limited but awesome sounding external plate or whatever reverberator to be shaped and filtered to make ambients, rooms, halls and experimental pseudo reverse or gate reverbs.
I made a bunch of presets tailored on my Davoli Krundaal Spring unit, they could have to be changed in the input and output levels to match your unit and your incoming sounds.
The device is designed with a stereo input for the instrument sound, but it manages a mono unit (the spring) so the internal path is monophonic but it emulates pseudo-stereo on the verb effect.
It doesn't pass the instrument sound to the stereo out, it must be used only as an aux effect, it's not insertable and has its own MIDI I/Os for control purposes.
It has a Left input only switch on the panel that is the most logical way to use it, taking a single mixer Aux out in the left input and returning a pseudo-stereo reverb from a stereo output. I've put a stereo input for feeding it directly from a stereo signal, in this case you switch off the Left only switch, but the two channels are mixed internally to feed a mono spring.
You have an input hipass, both for the sound to the spring and for the followers, it can work also just for one of the two.
The two followers both act on a lowpass filter for the verb signal, the second one works also for the amplitude shape of the returning reverb.
The image should explain all the routings well. put the preset file in the presets folder.
This is marked as beta 01, but here it works ok so far, anyway here it is!
Last thing: this device is not related with my collaboration with Adern in any way, it's an older idea.
Enjoy
(for the very few that probably need it 
)
Looks like a useful tool!