SV: Re: [sdiy] [SDIY] Faster Enveloppe Mod for Sixtrack ?

[karl dalen]

Try over clock the CPU! .-)
Make shure the 68B50 uart has its 500khz
maintained otherwhise your MIDI will go ape!.
Z80 can usuall be over clocked a bit.

KD


--- Tim Parkhurst <tim.parkhurst at gmail.com> skrev:

> On 9/17/05, David Moylan <dave at westphila.net> wrote: 
> > 
> > I believe those are Sample/Hold caps. The 4051 is an analog multiplexer
> > which is routing DAC generated CVs to the caps where they are stored.
> > If I recall the 3394 datasheet mentions that all the CV inputs are
> > buffered hi impedance so there is no additional need for S/H buffers.
> > You don't want to change those caps.
> > 
> > I don't think there's much hope in speeding up the envelopes as they are
> > CPU generated then just routed to the chip. Plus any cap that might
> > theoretically slow the envelope down is likely necessary to smooth
> > quantization of the envelope.
> > 
> > I was very interested in the 3394 for a while and stared at the
> > datasheet a lot. Who doesn't like a synth on a chip?
> > 
> > Dave Moylan
> > 
> > Frédéric Bourgeais wrote:
> > 
> > >Hi all,
> > >
> > >A friend who own a SCI sixTrack, wish faster Attack to control the output
> > >VCA.
> > >
> > >I took a look to schematics available here:
> > >http://www.geocities.com/SoHo/2163/ST_schem/
> > >
> > >And CEM 3394 datasheet here :
> > >http://www.synthtech.com/cem/c3394pdf.pdf
> > >
> > >3394's Pin 18 is used to control the Final Gain CV, but unfortunalty
> > >Enveloppes are CPU generated, so it's not easiest as swapping a capacitor
> > >to a smaller one with good old analogue synths...
> > >
> > >Is there a last chance for faster CV, simply playing on caps or resistor
> > >values on the input of the 6 sixtrack's 3394 (such C171,R136,C169 on U131
> > >pin 18 here: http://www.geocities.com/SoHo/2163/ST_schem/st_b1.gif )
> > >
> > >Does these componants are used to smooth the Enveloppe CV ( a bit like a
> > >glide ? )
> > >
> > >Thanks for your help
> > >Fred
> > >
> > >
> > >
> > >
> > >
> > 
> >  You might have better luck by building simple hardware EGs and adding 
> their outputs to the VCF and VCA CV inputs on the 3394 (yes, a nifty little 
> chip). There are however, two major drawbacks to this approach: First, 
> getting the right 'gate' signal to trigger the EGs would be a PITA (perhaps 
> from decoding the right address on the 4051s). Second, these EGs would not 
> be programmable, and even if they were voltage-controlled, there would be 
> little hope of adding these settings to the existing program (unless you 
> felt like doing a major rewrite of the Six's operating system). 
> 
> Tim (and I thought PITA was a type of bread) Servo
> -- 
> "Imagination is more important than knowledge." - Albert Einstein
>