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<DIV dir=ltr align=left><SPAN class=858432323-26122017><FONT color=#0000ff
size=2 face=Arial>That's an old version. I've replaced the two transistors
with another 2164 VCA, and you don't see the actual expo converting 2164 in that
schematic, but it takes the Expo VC output of the opamp and directly processes
the VCO core current.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=858432323-26122017><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=858432323-26122017><FONT color=#0000ff
size=2 face=Arial>The parts count really isn't that high. Almost all of
the parts on this schematic are input resistors and pots for controlling the
pitch, and these are all going to be required no matter what. The HFC
circuit requires two trimmers because my scheme adjusts both the slope and the
intercept of the correcting current, unlike most schemes which only control the
slope. This is the key to the Dixie's (and Rubicon's and Atlantis's)
excellent tracking. Again, even an all-in-one expo converter chip would
require external correction trimmers, because every VCO core has tracking
error.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=858432323-26122017><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=858432323-26122017><FONT color=#0000ff
size=2 face=Arial>I don't mean to presume anything about your design skills or
level of experience, but I think that if you really went carefully through a VCO
design, then you would realize that what you are asking for really wouldn't save
very much in terms of parts or labor, both in building and in
calibrating.</FONT></SPAN></DIV><BR>
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<FONT size=2 face=Tahoma><B>From:</B> Jacob Watters
[mailto:jacobwatters@gmail.com] <BR><B>Sent:</B> Tuesday, December 26, 2017
1:58 PM<BR><B>To:</B> David G Dixon<BR><B>Cc:</B> SDIY<BR><B>Subject:</B> RE:
[sdiy] Expo in one chip?<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=auto>Thanks David. Like this example posted on muffwiggler?
<DIV dir=auto><BR></DIV>
<DIV dir=auto><A
href="https://www.muffwiggler.com/forum/userpix/2077_dixie_cv_network_2.png"
target=_blank>https://www.muffwiggler.com/<WBR>forum/userpix/2077_dixie_cv_<WBR>network_2.png</A><BR></DIV>
<DIV dir=auto><BR></DIV>
<DIV dir=auto>That sovles the resistor contact issue, but it still has a high
part count. Is there no such thing as a chip with linear in on one pin and
expo out on another?</DIV></DIV>
<DIV class=gmail_extra><BR>
<DIV class=gmail_quote>On Dec 26, 2017 4:07 PM, "David G Dixon" <<A
href="mailto:dixon@mail.ubc.ca" target=_blank>dixon@mail.ubc.ca</A>>
wrote:<BR type="attribution">
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<DIV dir=ltr align=left><SPAN
class=m_-861058061474778718118420321-26122017><FONT color=#0000ff size=2
face=Arial>Yes, it's called the V2164, and it is available from Coolaudio in
bulk, or from many retailers (Small Bear, Mammoth, etc). It is a quad
exponential VCA chip. One VCA is used to temperature compensate
the expo, and another is used as the actual exponential converter. It
requires an external summing opamp. A third VCA can be used as a
precision high-frequency compensation current source, leaving the fourth VCA
for another use. This is how all Intellijel VCOs (which I designed)
are controlled, and they have a reputation in euro-land for very decent
tracking and stability.</FONT></SPAN></DIV><BR>
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<FONT size=2 face=Tahoma><B>From:</B> Synth-diy [mailto:<A
href="mailto:synth-diy-bounces@synth-diy.org"
target=_blank>synth-diy-bounces@<WBR>synth-diy.org</A>] <B>On Behalf Of
</B>Jacob Watters<BR><B>Sent:</B> Tuesday, December 26, 2017 12:49
PM<BR><B>To:</B> SDIY<BR><B>Subject:</B> [sdiy] Expo in one
chip?<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=auto>
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<DIV>
<DIV dir=auto>Expo conversion is require in almost all VCO, VCF and VCA
circuits. Matching transistors and getting the right tempco resistor to be
touching them so they are the same temp is a pain.
<DIV dir=auto><BR></DIV>
<DIV dir=auto>Has anyone ever made an expo conversion chip that had
everything required in one package? Is it still
available?</DIV></DIV></DIV></DIV>
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