<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content="text/html; charset=us-ascii" http-equiv=Content-Type>
<META name=GENERATOR content="MSHTML 8.00.6001.23588"></HEAD>
<BODY>
<DIV dir=ltr align=left><SPAN class=701095105-01082017><FONT color=#0000ff
size=2 face=Arial>Yes, I should have clarified. I use 2164 for all my
filters, so my stages are always inverting (because 2164 must terminate to
virtual ground).</FONT></SPAN></DIV><BR>
<BLOCKQUOTE
style="BORDER-LEFT: #0000ff 2px solid; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"
dir=ltr>
<DIV dir=ltr lang=en-us class=OutlookMessageHeader align=left>
<HR tabIndex=-1>
<FONT size=2 face=Tahoma><B>From:</B> Andrew Simper [mailto:andy@cytomic.com]
<BR><B>Sent:</B> Monday, July 31, 2017 6:37 PM<BR><B>To:</B> David G
Dixon<BR><B>Cc:</B> Michael Zacherl; synth-diy mailing list<BR><B>Subject:</B>
Re: [sdiy] HP from LP ?<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=ltr>On 1 August 2017 at 08:29, David G Dixon <SPAN dir=ltr><<A
href="mailto:dixon@mail.ubc.ca" target=_blank>dixon@mail.ubc.ca</A>></SPAN>
wrote:<BR>
<DIV class=gmail_extra>
<DIV class=gmail_quote>
<BLOCKQUOTE
style="BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote>As others have said, it depends on the filter.<BR><BR>For
a four-pole cascaded-stage filter, you can get four different
highpass<BR>modes by summing the filter stage outputs and the feedback +
input in<BR>various gain ratios. If the gain ratios are given for the
{Feedback+Input,<BR>Stage 1 Output, Stage 2 Output, Stage 3 Output, Stage 4
Output}, then:<BR><BR> 6dB HP: {1,1,0,0,0}<BR><BR>12dB HP:
{1,2,1,0,0}<BR><BR>18dB HP: {1,3,3,1,0}<BR><BR>24dB HP: {1,4,6,4,1}<BR><BR>
<DIV class=gmail-m_875026266185064484HOEnZb>
<DIV class=gmail-m_875026266185064484h5></DIV></DIV></BLOCKQUOTE>
<DIV><BR></DIV>
<DIV>A quick point to the uninitiated: This only works if each of the cascaded
stages is inverting, otherwise you will need to flip the sign of every odd or
even weight.</DIV>
<DIV><BR></DIV>
<DIV>Cheers,</DIV>
<DIV><BR></DIV>
<DIV>Andy</DIV></DIV></DIV></DIV></BLOCKQUOTE></BODY></HTML>