Comparing this unit with Erbe-Verb, feeding it short pings from QPAS: I can tell thereās some similarity in the topology, but the sound is really pretty different except in relatively narrow ranges.
Erbe-Verbās decay time goes far longer and more feedback-ier, and that also makes it softer and lusher and more reverb-like. Erbe-Verb never really sounds like a delay in a feedback loop, even at maximum size ā there are a few echoes but theyāre kind of scattered in a complex way rather than repeating regularly, and still somwhat diffuse even with Absorb at minimum. It can sound quite metallic at minimum sizes. But still, any āsustainā it has is very diffuse and reverby, if that makes sense.
Your unit tends to sound like a delay with a bit some neat scattering to it, especially as you lower the clock rate/multiplier to slower rates. It gets more metallic as you speed it up, but the diffusion just isnāt there to make it sound reverb-like.
Also the envelope follower on the Erbe-Verb isnāt patched into anything, it just goes to the āCV Outā jack; I often forget the feature is there. Itās not really an integral part of the sound as much as the modulation is, especially the āergoticā random modulation with shimmer. (That paper doesnāt mention the shimmer for some reason; I donāt know if itās a side effect of how the modulation is implemented or a little extra special sauce.)
Audio example:
I recorded this on Erbe-Verb with quasi-Karplus comb filter pings from Rainmaker. Absorb is at minimum, decay at about 2 oāclock (any higher and it will start to sustain infinitelyā¦ actually even at this setting thereās a little bit of sustain āleakingā), tilt is neutral, depth is zero.
Iām starting at maximum Size and working my way down to minimum. (Iām not touching the Decay knob, which seems to be feedback.) The odd pitch shifts on the tails of the first two pings were because I didnāt wait long enough for the decay to fade out before turning the knob 
Even the longest size is a scattered, complex pattern rather than a steady echo, and the complexity and āreverbnessā increases as feedback further scatters the already-scattered signal.
I think itād be an extreme challenge to really duplicate the Erbe-Verb, but maybe more reverb-like response is possible within the limitations of the ER-301ā¦
(BTW, this is the closest Iāve ever listened to the Erbe-Verb, especially with short pings that reveal a bit more about its characterā¦ so thanks for indirectly encouraging me to get to know it better 
)
