an old file of mine ...

Haible_Juergen#Tel2743 HJ2743 at denbgm3xm.scnn1.msmgate.m30x.nbg.scn.de
Fri Jan 19 23:16:00 CET 1996


From: "Haible J. ZFE BT SE 42" <Juergen.Haible at zfe.siemens.de>
To: "'analogue'" <analogue at magnus.acs.ohio-state.edu>
Subject: It finally works - first scanner impress
Date: Thu, 15 Dec 94 10:19:00 PST


Hi!

After some minor troubles (an opamp couldn't provide the current for
a reference voltage, and so on), my Interpolating Scanner finally works.
For all those who are interested, I will give You an overwiew of the
front panel, and my first sonic impressions.
The panel is 20cm x 12.5cm. On the top row, there are the 8 scanner
inputs. They are normalized, so that input #n gets the signal of input
#(n-1), if nothing is plugged in. This is useful, if you use less than
8 different input signals.
In the second row, there are 8 green LED's to indicate the scanner's
position. As the the VCA channels themselves, the LED's, too, are
controlled by triangle-shaped signals; you can actually see the
crossfading when one LED gets darker and the next one gets brighter.
The third row has 8 Input Level pots, one for each channel.
Below the 3rd row, on the left side, there is an "offset" switch, that can
normalize the first input with 10V DC. If no input jack is used, this
voltage feeds all channels. This is good for waveshaping effects.

[ and for CV shaping of course - exactly what the ramp generator
does! You even can leave out the VCA's and just sum up the
voltages from the pot's, if this waveshaping and ramp generator are
the only applications You have in mind. - JH, Jan. 1996 ]

The bottom row consists of 2 inputs "scan left" and "scan right", with
a modulation sensitivity pot for each input. There is, of course, a
Manual Scan pot, and 2 output jacks.

[ the Manual scan allows for anything between unipolar and bipolar
function, btw. And with the LEDs above each pot You always see
where You are at the moment.]

I have experimented with the following patches last night, which might
give You a slight idea of the possibilities of the Scanner:
(1) Used three different signals, all derivated from my OB-8's output,
for three scanner inputs: SEM-filter output, VariSlope Phaser/Filter output
and direct OB-8 output. With the Manual Scan knob I selected the initial
point (the SEM-filter, for example ). Then, with an LFO at the Scan Left
input, I scanned periodically between the signals. This gives nice crossfade
effects for rather different filter responses, or slight colour changes for
similar filter settings. (Different input levels were adjusted by the input
pots, to give smoothe fades.)
(2) A similar setting as in (1), but modulation with a percussive envelope.
I scanned from brighter to darker filters, and set the input levels of the
darker
filters successivly lower. This makes an additional VCA obsolete. The filter
sweeps can sound *very* different than commonly used HP/BP/LP filters ...
(3) Now I tried some Waveshaping. I switched the dc voltage to all inputs,
and set the levels for the 8 positions rather randomly. Then I fed a VCO
signal (Triangle) into one of the *Scan* (i. e. modulation) inputs. This
produced
some nice sounds known from other waveshaping techniques. I fed an LFO
into the second Scan input; now the range, where the waveshaping actually
took place, was periodically shifted. The result was a bit similar to pulse
width modulation, only with complex signals instead of pulses.
(4) I used the patch of (3), but replaced the dc bias with the VCO signal
(the
same VCO that was used for scanning) for one channel. Now, everytime
when the LFO drove the scanning into the region of this input, there were
sime kind of auto-ring-modulation colours.
(5) I even used chords as a modulation source. With simple intervalls like
5ths, I got some nice waveshaping distortion.
Then it was late at night, and I stopped myself from experimenting.
I was tempted to start again this morning, instead of going to work - but
no, here I am again, on my computer.

JH.






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