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<DIV dir=ltr align=left><SPAN class=608281300-12122018><FONT color=#0000ff
size=2 face=Arial>Roman,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=608281300-12122018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=608281300-12122018><FONT color=#0000ff
size=2 face=Arial>You're right. Your suggestion is superior. I was
simply unaware of what a complete shit-show all this digital circuitry is.
This is exactly the reason why I avoid digital solutions whenever
possible. This module should be a pretty straightforward application of an
analog multiplexer, but you are basically saying (and I concur based on my
experience) that I can't use such a thing for clean audio, and to me, that is a
sad indictment of these ICs. I'm now switching these DG408s about as
cleanly as is humanly possible, and they're still misbehaving. It
just shouldn't be this hard.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=608281300-12122018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=608281300-12122018></SPAN><SPAN
class=608281300-12122018><FONT color=#0000ff size=2 face=Arial>So, I'm going to
try to implement your idea, but I don't have the ICs I need. I'm also
still trying to understand exactly how the switching works. I'm
presuming that the 3914 must be in Dot mode, because only one comparator can be
on at a time for this to work, and therefore, this circuit ONLY works with 3914,
and cannot be implemented with a generic flash comparator
chain.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=608281300-12122018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=608281300-12122018><FONT color=#0000ff
size=2 face=Arial>So, I'm going to finish off the circuit as it is, because it
works pretty well, but I concede that I basically cannot use these fucked up
digital chips to switch active audio circuits, and will build the next one your
way.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=608281300-12122018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=608281300-12122018><FONT color=#0000ff
size=2 face=Arial>Cheers,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=608281300-12122018><FONT color=#0000ff
size=2 face=Arial>Dave</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=608281300-12122018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
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<DIV dir=ltr align=left><FONT size=2 face=Tahoma><B>From:</B> Synth-diy
[mailto:synth-diy-bounces@synth-diy.org] <B>On Behalf Of
</B>Roman<BR><B>Sent:</B> Tuesday, December 11, 2018 1:20 PM<BR><B>To:</B>
synth-diy@synth-diy.org<BR><B>Subject:</B> Re: [sdiy] Help, I'm Desperate!
(Charge Injection with DG408)<BR></FONT><BR></DIV>
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<DIV></DIV>
<DIV>I know it's too late, as the circuit at this stage has already gone
slightly different path, and I already gave up, but couldn't help drawing this
little schemo that explains my idea of using single switches with that
obsoleted chip. Switches should be DG444 or similar (0=closed, 1=open), or
replace diodes with NAND gates and use any regular dirt cheap switch like
4066.<BR></DIV>
<DIV>There's no switching happening while VCA is open, provided that VCA
control triangles match the edges of LM3914 stages. The only switched channels
are the ones routed to muted VCA, so in theory there should be no clicking
audible.<BR></DIV>
<DIV>Basicaly this is just the circuit that makes this input switching
sequence:<BR></DIV>
<DIV>VCA-A:12233445566..<BR></DIV>
<DIV>VCA-B:11223344556...<BR></DIV>
<DIV>by creating one step overlap between stages. Only 6 inputs in this
example, but can be extended to any other number.<BR></DIV>
<DIV><A
href="http://www.synthdiy.eu/files/scanner.png">http://www.synthdiy.eu/files/scanner.png</A><BR></DIV>
<DIV><BR></DIV>
<DIV>IMHO switching active channel will always produce some clicking for many
reasons: not matched channels, difference between transistion times H->L
and L->H as Ingo said, break-before-make feature of DG407, slow response of
4532, and who knows if not also charge injection.<BR></DIV>
<DIV><BR></DIV>
<DIV>Roman<BR></DIV>
<DIV class=nh_extra>
<P>Dnia 11 grudnia 2018 18:24 Ingo Debus <igg.debus@gmail.com>
napisał(a):<BR></P>
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<DIV>Am 11.12.2018 um 08:10 schrieb David G Dixon
<dixon@mail.ubc.ca>:<BR></DIV>
<DIV><BR></DIV>
<DIV>There is now<BR></DIV>
<DIV>only one tiny problem: There is still an almost imperceptible click
when the<BR></DIV>
<DIV>CV crosses 0V (and the logic control voltage crosses 2.5V) in the
positive<BR></DIV>
<DIV>direction. This is when the logic switches from 011 to 100
(i.e., all three<BR></DIV>
<DIV>bits change). Interestingly, I don't hear the click at all when
the CV goes<BR></DIV>
<DIV>in the other direction (100 to 011).<BR></DIV></BLOCKQUOTE>
<DIV><BR></DIV>
<DIV>Couldn’t this still be caused by a very brief „forbidden state“ during
the transition from 011 to 100? In your case, the forbidden state would be
000 (MSBit changes slower that the other two) or 111 (MSBit changes faster).
Probably just a difference between rising and falling slope. Can you check
with a scope?<BR></DIV>
<DIV><BR></DIV>
<DIV>Ingo<BR></DIV>
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