[sdiy] Moog-type highpass filter

[cheater cheater]

Antti,
> I believe it's simply marketing speak for "Add user adjustable gain before
> and after the filter".
yes, but both pre-gain and post-gain are in a single control for ease
of use (I know it won't be exactly unity gain, it was just a
shorthand).

Harry,
> Which I have on one of my diy synths... there are separate pots for each
> VCO and a master volume after the filter. It was intended for a theremin
> so there is ~no~ VCA at all.

Correct me if I'm wrong, but wouldn't that just overdrive the input
stage? That means for example IC3b on this schematic:
http://yusynth.net/Modular/Commun/MOOGVCF/Moogfilter-sch.jpg

I wasn't really even talking about overdrive - just about having
enough AC peak-to-peak current so that it can modulate the
transistors' resistance in a significant way. I understand that
'normally' the AC signal's peak to peak current difference is orders
of magnitude lower than the swing of the 'control' DC current.

Cheers,
D.

On Thu, Apr 22, 2010 at 16:49, Antti Huovilainen <ajhuovil at cc.hut.fi> wrote:
> On Thu, 22 Apr 2010, Amos wrote:
>
>> "LPF that can amplify the (AC) signal  while it's going through the
>> ladder,
>> while keeping the whole effect at
>> unity gain."
>>
>> Do the laws of nature allow such a thing?
>
> I believe it's simply marketing speak for "Add user adjustable gain before
> and after the filter". Aka "drive" control.
>
> Antti
>
> "No boom today. Boom tomorrow. There's always a boom tomorrow"
>  -- Lt. Cmdr. Ivanova
>