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<P><FONT size=2><FONT face="Courier New">I have both 4-channel and 8-channel
interpolating scanners that work perfectly and are not terribly
parts-intensive. You can see YouTube demonstrations of them
here:<BR><BR>My "simple" 8-channel scanner, is shown here:<BR><BR></FONT><A
href="https://www.youtube.com/watch?v=hZGskck31hs"><FONT
face="Courier New">https://www.youtube.com/watch?v=hZGskck31hs</FONT></A><BR><BR><FONT
face="Courier New">There is also a slightly less parts intensive 4-channel
version. This module works by controlling a single linear crossfader to
process two adjacent channels in a group of 8 (or 4) channels. The
scanning is completely seamless and can be done at audio rates with no
glitching.<BR><BR>My older 4-channel scanner design with variable width and
spacing of the control trapezoids, is shown here:<BR><BR></FONT><A
href="https://www.youtube.com/watch?v=Hf_KCZX1fcQ"><FONT
face="Courier New">https://www.youtube.com/watch?v=Hf_KCZX1fcQ</FONT></A><BR><BR><FONT
face="Courier New">The beauty of this older design (which I've just redesigned
and built again in Euro format for a local synth enthusiast here in Vancouver)
is that it can be built just as a trapezoid generator, and used to drive any
quad-VCA module (such as the Intellijel Quad VCA, or two Intellijel
uVCAs). This option involves very little circuitry. I've redesigned
this circuit to put not only the fader, but also the trapezoid width, under
voltage control, and I use an onboard linear VCA to keep the trapezoids
perfectly within the fader field regardless of the width control. This
scanner can be adjusted to go from complete overlap of all channels to
significant separation (with dead-space in between) of the channels.
Regardless of the width setting, Channel 1 will come on from the bottom of
the fader, and Channel 4 will just disappear at the top of the
fader.<BR><BR>I will happily share schematics for these circuits, or make PCBs
for a very reasonable price (through-hole Doc Sketchy specials -- not terribly
small, but a real pleasure to stuff and solder). For a bit more moolah I
will happily stuff and test the boards, and for a bit more, I will install them
behind 5U panels. If you are a Eurorack user, I can do that too, but the
modules are pretty deep. Here's a couple pictures of my eurorack 4-channel
variable width scanner buddy (for external VCAs) that I just delivered two days
ago:<BR><BR><IMG border=0 hspace=0 alt="" align=baseline
src="cid:726180818@03122020-0BF1"><FONT color=#0000ff face=Arial> <IMG
border=0 hspace=0 alt="" align=baseline
src="cid:726180818@03122020-0BF8"></FONT></FONT></FONT></P>
<DIV><FONT size=2><FONT face="Courier New">The top board (the one you can see)
is the trapezoid generator -- four identical circuits generating -0.6V to +5.0V
trapezoids at different locations on the main CV ramp to turn on a linear VCA
(assuming the VCA is at unity gain when the CV is 5V). The bottom board
(which you can't see) is the CV control board, processing the panel controls and
CV inputs to generate the voltages to control the position and width of the
trapezoids. These boards are 2.1" wide and 3.5" long, and they plug into
each other. I made this circuit on two boards to accommodate
Eurorack. I could rearrange the various inputs and outputs so that it
would actually plug into the panel PCB in true Eurorack style, but I was in a
hurry to get this done.</FONT></FONT></DIV>
<DIV><FONT size=2><FONT face="Courier New"></FONT></FONT> </DIV>
<DIV><FONT size=2><FONT face="Courier New">So, if you watch the second video,
you will notice that the width control (the red knob) alters the width of the
fader field such that the CV must be adjusted to put all the voices in the field
symmetrically. I've solved that problem with my new circuit. To
demonstrate, the following plots show the position and width of the control
trapezoids across the entire fader range as a function of the Width voltage
(which I called "Range" in the video):</FONT></FONT></DIV>
<DIV><FONT size=2><FONT face="Courier New"></FONT></FONT> </DIV>
<DIV><FONT size=2><IMG border=0 hspace=0 alt="" align=baseline
src="cid:726180818@03122020-0BFF"><IMG border=0 hspace=0 alt="" align=baseline
src="cid:726180818@03122020-0C06"><IMG border=0 hspace=0 alt="" align=baseline
src="cid:726180818@03122020-0C0D"><IMG border=0 hspace=0 alt="" align=baseline
src="cid:726180818@03122020-0C14"></FONT></DIV>
<DIV><FONT size=2><FONT color=#0000ff face=Arial></FONT></FONT> </DIV>
<DIV><FONT size=2><FONT face="Courier New">Notice how Channels 1 and 4 just
appear and disappear at the bottom and top of the fader range, respectively, no
matter the Width voltage. This involved a bit of
algebra.</FONT></FONT></DIV>
<DIV><FONT size=2><FONT face="Courier New"></FONT></FONT> </DIV>
<DIV><FONT size=2><FONT face="Courier New">Anyway, back to your previously
scheduled programming....</FONT></DIV>
<P><BR><BR><BR><BR><BR><FONT face="Courier New">-----Original
Message-----<BR>From: Synth-diy [</FONT><A
href="mailto:synth-diy-bounces@synth-diy.org"><FONT
face="Courier New">mailto:synth-diy-bounces@synth-diy.org</FONT></A><FONT
face="Courier New">] On Behalf Of Joel B<BR>Sent: Thursday, December 03, 2020
1:30 AM<BR>To: Synth-diy@synth-diy.org<BR>Subject: [sdiy] CEM3340
question<BR><BR>[CAUTION: Non-UBC Email]<BR><BR>The Behringer Neutron uses two
3340s but it has a feature that I’m not seeing in the CEM3340 data sheet -
voltage controlled wave shape - you can sweep between four different shapes.
It’s a little glitchy unless you modulate at a fairly low frequency. Yet when I
look at what is available otherwise, especially in Eurorack format using this
chip, nothing has that feature.<BR><BR>How did Behringer implement
that?<BR><BR>Joel<BR><BR>Sent from my
iPhone<BR><BR>_______________________________________________<BR>Synth-diy
mailing list<BR>Synth-diy@synth-diy.org<BR></FONT><A
href="http://synth-diy.org/mailman/listinfo/synth-diy"><FONT
face="Courier New">http://synth-diy.org/mailman/listinfo/synth-diy</FONT></A><BR><FONT
face="Courier New">Selling or trading? Use
marketplace@synth-diy.org<BR></P></FONT></FONT></BODY></HTML>