Doepfer A-138o

Bought this to go with an A138p (as it has to!). As with all things Doepfer is does exactly what it says on the tin. The only downside is that the auxiliary in/out is mono - and considering most of what you'd send via a solitary bus in modular land would be reverb, that's a little limiting. But beyond that, everything else is as you'd want: solid build quality, transparent sound, etc.