[sdiy] CEM3328 seems to only have buffers at the end

[Antti Huovilainen]

On Tue, 21 Feb 2006, Antti Huovilainen wrote:

> On Tue, 21 Feb 2006, JH. wrote:
>
>>> However, the
>>> distortion cancellation in OTA filters (for similar signal levels at OTA
>>> input / diff pair input) is so effective that any distortion in the
>>> resonance feedback loop dominates the behaviour.
>
> Simply put, if you have 4 pole moog ladder and 4 pole OTA filter set up so 
> that the filter core input voltages (after resistor ladder) are same, the OTA 
> is much cleaner. Therefore at self oscillation / high resonance the signal 
> level is higher than in Moog and any clipper in resonance path has higher 
> effect than in Moog.

They say a picture says more than a thousand words:
http://www.acoustics.hut.fi/~ajhuovil/selfosc.png

That is a simulation of filter in self oscillation starting as Moog and 
then switching to OTA at halfway. The only nonlinearities are in the 
filter core.

0.5 on y scale = Vt = 25mV

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova