Interest Jurgen's Scanning Interpolator PCB?

[Henri Kovalainen]

 Thanks to Juergen for sharing the idea with all of us, but still, I would
 suggest that everybody takes a look at Don's alternative design at

 http://www.till.com/articles/scanner/index.html

 atleast before anyone starts designing boards for the thing. IMHO this
 version seems much more attractive, as I have been told that with 
 moderate matching of the trannies, one can achieve satisfying results.

On Sun, 4 Apr 1999 WeAreAs1 at aol.com wrote:
> I haven't looked at the schematics lately, so I don't remember if the circuit 
> is DC-coupled (for scanning LFO outputs).  Is it, Juergen?  If not, could it 
> be?

 There's no reason why the VCAs wouldn't be DC-coupled. Indeed, this is
 required for the type of use I'm looking forward to. You see, by feeding
 offset voltages to the VCA inputs (most conviniently done with vertical
 sliders) and scanning them with a VCO output, we have total control of
 the resulting wave. However, the VCA inputs can be used for any type of
 signals (not just static voltages) so there are actually no limits to the
 amount of animation we want to apply to the output. Further more, the
 scanning signal doesn't have to be a simple repetitive wave either.

 Actually by feeding in an audio signal we have, just by the sliders, full
 control over the "transfer curve" of the dynamics in the signal. I would
 certainly like to try, what kind of distortions are you able to do with
 something like this? Although, I have no idea what the signal would sound
 like, because of the fact that we have only 8 steps and the space between
 them is practically linear. I guess we could build a scanner with more 
 steps, but I'll try the 8 step version first. Has anybody who actually
 has one ever tried this? 

 Then again, with much more inputs, it would probably be appropriate to 
 change the whole design, so that we would have only 2 VCAs, and the
 input in question would be muxed into the required VCA. Then the two VCAs
 whould fade between each other as the next (or prior) input is switched
 in and so on... In this case I would be easier to implement control on
 the fade curve, and even the order in which the inputs are used.
 However, designing a circuit that would be able to do this at high audio
 frequencies is, alas, far beyond my skills.

 It's a pity that in the traditional design, there doesn't seem to be
 any simple way to gain control over the fading curve of each step, this
 would make things even more interesting. Btw, if we fed a part of the
 current that controls the VCA back into the scanning voltage (as voltage
 ofcourse), what kind of effect would this have on the curve of the 
 particular step?

 I have seen some graphic eqs with sliders that have a tiny led in each
 slider pot. Does anybody know where I could buy these kind of sliders?
 Would sure be a killer place for the step indication led!

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