[sdiy] Module Placement - Dist > Filter or vice versa

[Roy J. Tellason]

On Thursday 18 November 2004 01:49 pm, Scott Gravenhorst wrote:
> "Roy J. Tellason" <rtellason at blazenet.net> wrote:
> >On Thursday 18 November 2004 12:26 am, William Berzinskas wrote:
> >> i'm building a simple efx unit using a few things lying around..  i've
> >> got 2 distortion units  selectable via switch..   one is tube overdrive
> >> sim and the other strait distortion.   i'm also going to add a cd4007
> >> based filter in there..
> >
> >What kind of a filter can you base on a 4007?

> Pretty much like a 4069UB filter.

I don't recall running across that one either,  though I might have and just 
don't remember...

> The 4007 contains three inverters which can be used as integrators.  If the
> input is sufficiently attenuated, you can also use a 4007's N transistors as
> voltage controlled resistors.  (the attenuation required is no worse than
> that used for OTA filters).

That sounds pretty nifty.  I'm really surprised that there doesn't seem to be 
any simple way to control amplitude with voltage,  and hasn't been for as 
long as I've been looking.  How low of a signal level are we looking at 
there?  I never did get much of a handle on OTAs though I have a few to mess 
with here,  both 3080 and 3094...

> I'm still sitting on a design myself, 4069UB for the integrators and H11F1
> for the resistive elements.  Schematic is done, gotta get my ass in gear and
> breadboard the thing.  I chose H11F1 rather than 4007 or 4069 because the
> H11F1 eliminates virtual ground problems AND the H11F1 distorts
> symmetrically (when driven with more than 100mv Vds) according to my own
> testing.

Sounds interesting,  I'd like to hear more about this once you get around to 
getting  going with it.