Wiardgroup

> 
> - does the type knob permit smooth transitions from LP to BP to HP? 
> If so, if this CV controllable in any way?

Yes, unlike other Sallen-Key designs, the Borg uses a pan pot to tranverse from LP to BP to 
HP. It is very smooth and resonance (peaking) is constant. All other designs use a switch 
for this function.

CV control would add a great deal of expense. Doubling the cost of the module.

Panning from LP to HP in performance sounds a somewhat like adding a phaser. The first 
synth to have this function was the EML 101. But that was a very primative state variable 
filter with an unobtainium tapped potentiometer. The Borg inplementation is much more 
elegant.

Personally I find state variable filters to be completely boring. Although the SEM used one 
and some people like it. For musical drama, a Sallen-Key (Borg) or Butterworth 4 pole 
(Boogie) gives much better results.

Five years ago I prototyped a state variable filter made with Vactrols and it was so "plain 
vanilla" I almost cried. Painfully unexciting.

> - is the control range knob an attenuator for control in?  If so, is
> this the only difference between control in and key in?
> 

Yes the Control Range knob is the attenuator for control in. The Key(board) input is 
nominally
1 volt per octave. It is use when you want ot have the filter track the keyboard for a 
constant spectrum.