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My grandson plays an ordinary accoustic cello but thank you for your interest.
The type of device I have in mind takes a mic or high level feed in and the reverberation acts on that signal alone, with an output high enough to drive a speaker, it may have several different input channels of course but I would only need a more simple device with just the one channel if that's all that is available but the number of inputs is not a problem.
Of course things may have changed but those I used before I retired from the profession were just as I've described, assuming of course that they were 'rack' mounted and not part of a sound mixing desk. where each cnannel has it's own reverberation 'send'
Musicator