BassStation Filter: What is it?

[Rob]

Well, I remember way back when, I looked into the unit and I didnt see the
telltale signs of a ladder filter ie neat rows of transistors/capacitors.
Unfortunately, I don't have one on hand to check out right now.. I am sure
once the rack unit I bought comes in, it will prlly only take me an hour
with my scope to figure the thing out.

Also, a state variable filter would definitely be easier to produce the 2
pole/4 pole configuration that they used.

As far as the VCO, I question whether it has a VCO at all. I get the feeling
that it has a DCO driven from lookup tables in the uP.. I dont remember it
ever going out of tune, so this would point to to a uP DCO.

Nothing wrong with this, but you definitely don't get the warmth of analog
with the DCO.. Still sounds good, but just a bit too perfect.

Thanks

Rob

----- Original Message -----
From: <metamatic at webtv.net>
To: <synth-diy at node12b53.a2000.nl>
Sent: Saturday, November 25, 2000 8:51 PM
Subject: Re: BassStation Filter: What is it?


> cyborg_0 at iquest.net wrote:
>
> >Anyone know what kind of filter is
> >crammed in there? From what I
> >remember, it was some sort of state
> >variable filter, but I am not all that sure.
>  >Perhaps someone has some schematics?
>
>  I have the keyboard version. The VCF has two modes, both lowpass. The 2
> pole mode is meant to suggest a TB-303 filter, somewhat unconvincingly,
> IMO. The 4 pole mode, however, does a wonderful job of emulating a Moog
> VCF. I think it sounds quite a bit like my ancient Source, and along
> with the bonus of factory MIDI, I don't have to worry about damaging a
> rare membrane switch panel.
>
>  I'd love to see schematics as well, if only to see how the different
> cutoff slopes are achieved.
>
> Richard Hess
>
> metamatic at webtv.net
>
>