BassStation Filter: What is it?

Harry Bissell harrybissell at prodigy.net
Mon Nov 27 00:27:47 CET 2000 

Hi all...

I doubt the filter is near the Wasp. Check out JH's clone of the Wasp... its a
state
variable and the Bass Station is probably a 4 pole cascade, tapped at the 2 pole

point (more like the CEM3320...)

If you want a great sounding flange, take two digital delay lines (a matched
pair is
even nicer) and send the signal through wach in parallel. Set one for a fixed
delay
(like 2mS) and sweep the other through the 2mS point.  Sum both delay lines out
of phase... no original signal mixed in. True through zero flanging !!! which is
where
most DDLs screw up.

Opamp / OTA is a phaser... its really not a time delay effect per-se, but if you

cascade enough stages it gets to be that way...

Rob wrote:

> As far as the Bassstation, I wonder how closely related the filter is to the
> EDP Wasp filter? I would guess fairly close in both sound and function, but
> I am not sure.
>
> As far as BBDs, with a BBD you have more options to access what is going on
> with it without having to buy an expensive DSP devkit or learn to code,
> although a friend of mine says that delay based FX are extremely easy to
> implement with a DSP and that they actually have code you can copy and paste
> into certain low end DSPs devcards that are free if you show up to the
> seminar.
>
> I oftentimes wonder what the Electrix MoFx woulda sounded like had they used
> some nice analog distortion.. I cannot BELIEVE they marketed a product with
> such an aweful noisy distortion section.. It should be an option just to
> have that damn thing removed..
>
> Plus, too, digital flange just never sounds all that great, and from what I
> have seen it can use either a BBD or an opamp/ota based delay scheme which
> always sounds better.
>
> There is a real reason why digital flange sounds crappy, something like FPU
> overrun or something like that and has to do with a limitation of the signal
> representation in a digital system.
>
> Thanks for listening to my tripe
>
> Rob
>
> ----- Original Message -----
> From: "Harry Bissell" <harrybissell at prodigy.net>
> To: "Bjorn Julin" <bnillson at hotmail.com>
> Cc: <a0284520 at addcom.de>; <synth-diy at node12b53.a2000.nl>
> Sent: Sunday, November 26, 2000 3:33 PM
> Subject: Re: BassStation Filter: What is it?
>
> > If this is the one I'm thinking of... the CPU sets a rough current
> > source charging a cap, and the counter tick is the reset pulse to
> discharge
> > the cap...
> >
> > so this way the sawtooth is pure linear (no steps) and the frequency is
> > pure digital...  any errors show up as amplitude variation. Nice way to
> go.
> >
> > I have no problem with digital oacillators either, except they are really
> hard
> > to modulate with CV's....  Its funny that it is the imperfections in real
> analog that
> > everyone likes....
> >
> > For some things I prefer digital... like digital delay lines.  BTW I
> consider the
> > BBD a digital delay, albeit a Sh!tty one. The fact that it has an analog
> range of
> > oh... a couple volts in the Y axis does not cover up the sampled data
> nature of
> > the X axis....  so just saying analog does not mean good !
> >
> > (if this don't draw some flames then the list is dead....;^)
> >
> > H^) harry
> >
> > Bjorn Julin wrote:
> >
> > > Yeah, there it is,one thing that are missing
> > > are the DCO tickers, they are created in a
> > > wery odd MCU, from matshusita if i remember right.
> > >
> > > No wave tables just a counter tick to a integrator
> > > who charges in a odinary whay to create sawtoth.
> > >
> > > I remmber the "OLD and "LIVELY" discussion on diy list
> > > about why a DCO was a VCO, and the reverse,in my opinion
> > > there is absolutely nothing wrong whit DCO's,in my
> > > opinion i prefer them "if" high enough resoulution
> > > of the charge ticks are used. Besides DCO'dont soft
> > > sync. :-)
> > >
> > > Thanks for the link!
> > >
> > > Reg
> > > BJ
> > >
> > > >you are all in luck....
> > > >
> > > >http://www.asahi-net.or.jp/~WZ4K-TNK/syoyuu/bsk.html
> > > >
> > > >Rob wrote:
> > > >
> > > > > 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
> > > > > >
> > > > > >
> > > >
> > > >--
> > > >mark verbos
> > > >
> > > >"if you want something done right, build it yourself."
> > > >
> > > >verbos at simple-answer.com
> > > >www.simple-answer.com
> > > >
> > > >watch out for...
> > > >on my new label SIMPLE ANSWER "only a danger to myself"  and "Culture
> > > >Shock"
> > > >out now.
> > > >also...
> > > >coming soon "World of Illusion" Simple Answer 003 now distributed by
> > > >Integrale,
> > > >UK
> > > >I have moved to Berlin!
> > > >
> > > >
> > >
> > >
> ____________________________________________________________________________
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