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<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial>Hi Elain,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial>You should check out the frequency responses for the
Intellijel Polaris filter (which I designed) here:</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial><A
href="https://intellijel.com/wp-content/uploads/2015/12/Polaris-Frequency-Responses.pdf">https://intellijel.com/wp-content/uploads/2015/12/Polaris-Frequency-Responses.pdf</A></FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial>You will notice that three of the bandpass modes (B, C, and E)
are asymmetrical, with different slopes on either side of the corner
frequency. The bandpass modes can put different numbers of poles on either
side. Hence, for a four-pole filter, the possibilities are: 1/1, 1/2, 1/3,
2/1, 2/2, and 3/1. The five bandpass modes available on the Polaris are as
follows:</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial>BP A = 1/1 (symmetric)</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial>BP B = 2/1 (asymmetric)</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial>BP C = 3/1 (asymmetric)</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial>BP D = 2/2 (symmetric)</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=158171707-11062018><FONT color=#0000ff
size=2 face=Arial>BP E = 1/3 (asymmetric)</FONT></SPAN></DIV>
<DIV><FONT color=#0000ff size=2 face=Arial></FONT> </DIV>
<DIV><SPAN class=158171707-11062018></SPAN><FONT face=Arial><FONT
color=#0000ff><FONT size=2>T<SPAN class=158171707-11062018>he
1/2 bandpass mode is not available on the Polaris, because the
powers-that-be at Intellijel didn't want to include it for whatever reason (it
was probably too similar-sounding to one of the others). These modes are
obtained by summing the four individual stage outputs of a
cascaded-stage (Roland-type) filter in precise gain
ratios.</SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=158171707-11062018></SPAN></FONT></FONT></FONT> </DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=158171707-11062018>Also, there are some interesting notch and double-notch
modes available on the Polaris which will give something like asymmetric
bandpass filtering when resonance is employed. Some of these modes may get
you close to the instrumental timbres you are looking
for.</SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=158171707-11062018></SPAN></FONT></FONT></FONT> </DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=158171707-11062018>Cheers,</SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=158171707-11062018>Dave Dixon</SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT color=#0000ff size=2 face=Arial></FONT><BR></DIV>
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<HR tabIndex=-1>
<FONT size=2 face=Tahoma><B>From:</B> Synth-diy
[mailto:synth-diy-bounces@synth-diy.org] <B>On Behalf Of </B>Elain
Klopke<BR><B>Sent:</B> Sunday, June 10, 2018 10:43 PM<BR><B>To:</B> *SYNTH
DIY<BR><B>Subject:</B> [sdiy] Filter slopes<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=ltr>
<DIV>Hey all,</DIV>
<DIV><BR></DIV>I was reading an article about the spectral content of various
instruments (woodwinds and strings) and while they didn't have any circuits,
there were some tables showing cutoff frequencies and high and low slopes.
Several of the pictures looked like bandpass filter responses with different
slopes on each side. How would I go about doing that? Is the slope determined
by the gain of the op amp in an active filter? If it's that easy, would it be
a highpass filter followed by a lowpass filter each with their own gain
settings?
<DIV><BR></DIV>
<DIV>-Ian</DIV></DIV></BLOCKQUOTE></BODY></HTML>