diode ladder vs. tr. ladder ?

[Don Tillman]

   From: Martin Czech <martin.czech at itt-sc.de>
   Date: Tue, 23 Sep 1997 07:33:53 +0200 (MET DST)

   Someone asked if diode ladders sound different than transistor
   ladders.  The answer was that the poles of the d.l. are all
   different whereas the t.l. poles are at the same location. Cranking
   up resonance means imidiately complex poles (in an X-shape) for the
   t.l., but the d.l. poles stay real for a while, before spreading
   out from the real axis. This would be a difference for shure.

Yes indeed.

   But, is this not just a question of dimensioning? I think it should
   be possible to get the same resonance behaviour out of both types,
   since diode and transistor represent current controlled
   conductances (1. order explanation), so it depends more on the
   filter caps (root locus).

You mean adjust the cap values on the diode ladder so that all four
poles are tuned together?  Sure, that could work.  I've never heard of
that being done.

   Do parasitic effects have such an influence that the circuits
   (poles) will never behave the same way?

It's more than that.

The nonlinearities and dynamic motion of the poles with overdriving
will still be a little different because the way the circuit works is
a fundamentally different process.  

Is this enough to be audible?  I dunno.  (Okay guys, into the lab!)

  -- Don