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<DIV dir=ltr align=left><SPAN class=997425121-15122020><FONT color=#0000ff
size=2 face=Arial>Because 7.07k is the square root of 1/2 times 10k.
The closest resistor in E96 is 6.98k. Actually, using 11.5k and 16.2k
gives a ratio of 0.710, and is as close as one can get to 0.707 in the E96 (1%)
series or resistors.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=997425121-15122020><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=997425121-15122020><FONT color=#0000ff
size=2 face=Arial>The panpot attenuates 7.65dB at the midpoint, and the opamps
amplify by 4.65dB, to give 3dB net attenuation at the midpoint (about
71%).</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=997425121-15122020><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN><SPAN class=997425121-15122020><FONT
color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=997425121-15122020><FONT color=#0000ff
size=2 face=Arial>For the "compromise" law which is 4.5dB attenuation at the
midpoint, one would want a resistor ratio of 2.14, so the 7.07k resistors
would be replaced with 21.5k (the closest value in E96), or use 10.7k and 4.99k
resistors to get even closer. Now, the panpot attenuates by 14.5dB at
the midpoint, and the opamps amplify by 10dB, to give 4.5dB net attenuation at
the midpoint (about 60%).</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=997425121-15122020><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=997425121-15122020><FONT color=#0000ff
size=2 face=Arial>I don't know for sure, but I suspect that if "linearized" 2164
circuits were used in place of the pan pot, the signal bleed because of the
wiper contact resistance that Douglas Self worries about could be eliminated,
because the VCA could be fully turned off.</FONT></SPAN></DIV><BR>
<DIV dir=ltr lang=en-us class=OutlookMessageHeader align=left>
<HR tabIndex=-1>
<FONT size=2 face=Tahoma><B>From:</B> Didier Leplae
[mailto:didierleplae@yahoo.com] <BR><B>Sent:</B> Tuesday, December 15, 2020 1:36
PM<BR><B>To:</B> Mattias Rickardsson<BR><B>Cc:</B> David G Dixon; Synth
DIY<BR><B>Subject:</B> Re: [sdiy] Panning (again)<BR></FONT><BR></DIV>
<DIV></DIV><SPAN
style="BACKGROUND-COLOR: #ffecb3; COLOR: #000000; FONT-SIZE: 12px"><SPAN
style="BACKGROUND-COLOR: #ffecb3; COLOR: #000000; FONT-SIZE: 12px"><SPAN
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Non-UBC Email]</SPAN></SPAN></SPAN>
<DIV dir=ltr>Out of curiosity, why 7.07k resistors? That seems like such a
specific value</DIV>
<DIV dir=ltr><BR>
<BLOCKQUOTE type="cite">On Dec 15, 2020, at 3:27 PM, Mattias Rickardsson
<mr@analogue.org> wrote:<BR><BR></BLOCKQUOTE></DIV>
<BLOCKQUOTE type="cite">
<DIV dir=ltr>
<DIV dir=auto>
<DIV dir=auto>Douglas Self shows this connection as the first example in the
Passive Panpots subchapter of his Small Signal Audio Design book, with the
description
<DIV dir=auto>"... has several disadvantages, not least the poor offness when
panned hard over, caused by the current flowing through the wiper contact
resistance to ground."</DIV>
<DIV dir=auto><BR></DIV>
<DIV dir=auto>The rest is left to the reader, but thanks to separated L/R
channels with law-bending resistors, the story ends well. And most of you have
already figured out that the next subchapter is even better. ;-)</DIV>
<DIV dir=auto><BR></DIV>
<DIV dir=auto>/mr</DIV></DIV><BR>
<DIV class=gmail_quote>
<DIV dir=ltr class=gmail_attr>Den tis 15 dec. 2020 19:34David G Dixon <<A
href="mailto:dixon@mail.ubc.ca" rel="noreferrer noreferrer"
target=_blank>dixon@mail.ubc.ca</A>> skrev:<BR></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote><U></U>
<DIV>
<DIV><FONT size=2 face=Arial><SPAN>Hey Team,</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN>I've been thinking about this panning
thing, and I came up with the following very simple pot-based panning
circuit:</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN><IMG border=0 hspace=0 alt=""
align=baseline src="cid:893392018@15122020-2191"
data-unique-identifier=""></SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN>The gain responses of this circuit are
shown below, and compared with sin and cos responses:</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN><IMG border=0 hspace=0 alt=""
align=baseline src="cid:893392018@15122020-2198"
data-unique-identifier=""></SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN>I believe that I can create a
voltage-controlled version of this simple pot panning circuit fairly easily
by replacing the pot with a pair of modified Irwin 2164 circuits. I
did this for the Morphing LFO.</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN>Would this response suffice as an "equal
power"
panner?</SPAN></FONT></DIV></DIV>_______________________________________________<BR>Synth-diy
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<DIV><SimplePanner.png></DIV>
<DIV><PanPlot.png></DIV><SPAN>_______________________________________________</SPAN><BR><SPAN>Synth-diy
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