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

[jhaible at debitel.net]

> > But you have so many degrees of freedom to design these filters.
> > Especially when you're using OTA filters with buffers and resistor
> > dividers, you can set your "working level" (and the clipping which
> > would occur in another OTA for feedback) just as you like.
> 
> Nitpicking, but the same goes for Moog.

Yes, obviously.


> Input divider sets core level, 
> output differential amplifier the resonance distortion (usually pretty 
> low when opamp is used for this).

Yes, but your original mail said something like in OTA filters, the distortion
would be dominated by the feedback distortion. That's what I didn't get, with
all the variations that are possible. So that statement about the feedback 
distortion dominating in OTA filters, but not in ladder filters, would apply
to a setting where the feedback rounding is somewhat between the rounding
of ladders and the rounding of OTAs, and for such a setting only.

> I _think_ (read: I've done a few spice simulations but nothing conclusive) 
> what happens here is that the base-collector diode becomes active when 
> capacitor voltage goes below diff-pair - input. This is somewhat similar 
> to tube amplifiers where the grid also acts as a diode thus varying 
> the DC voltage over the interstage DC blocking capacitor.

Yes.

JH.

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