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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Well, I know that the higher-Q filters
have a longer delay, so that they take longer to respond to the incoming
waveform. I’m thinking that a Q of about 3 is probably about right, and with
that, only a 4-pole filter is required.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I’ve got a nice design for an envelope
follower which responds quickly and has little or no ripple, so that’s not a
problem.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>On a related note, does anyone here have
problems getting the Bode plotter in Multisim to work consistently? I am
finding with this simulation that sometimes if I change the component values, the
Bode plotter doesn’t work at all. Also, for some simulations, changing the
component values doesn’t change the filter response at all. Multisim is sure
glitchy. It’s very frustrating. I can sometimes fix it if I erase all of the
passive components and load new ones with the new values, rather than just
changing them, but that sort of thing is just complete bullshit. Multisim is a
sad excuse for a professional program. There must be something better out
there (?).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> Paul Perry
[mailto:paulfrancisperry@gmail.com] <br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, August 30, 2019
10:22 PM<br>
<b><span style='font-weight:bold'>To:</span></b> David G Dixon<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [sdiy] vocoder
filters</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>I don't think there is a "right" answer. To my mind, it
depends on what one wants to do with the unit. Think about what will happen
when a single swept tone is used to modify white noise. The low pass filter on
the VCAs probably has a significant effect as well.<o:p></o:p></span></font></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>paul perry <st1:City w:st="on">Melbourne</st1:City> <st1:country-region
w:st="on"><st1:place w:st="on">Australia</st1:place></st1:country-region><o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>On Sat, 31 Aug 2019 at 14:50, David G Dixon <<a
href="mailto:dixon@mail.ubc.ca">dixon@mail.ubc.ca</a>> wrote:<o:p></o:p></span></font></p>
</div>
<blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;
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<div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>Well, I think I might have answered my own question. Looking
again at the JH Living Vocoder, since Jurgen Haible’s filter responses overlap
at about the 8dB mark, it really should not matter at all what’s going on
around the skirt of the response, and higher-Q filters with two 2-pole stages
should give very similar results to low-Q filters with four 4-pole stages (and
be much much cheaper to build).</span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'> </span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>I’d still appreciate if anyone has any specific insights into this
problem. Cheers.</span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'> </span></font><o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;font-weight:
bold'>From:</span></font></b><font size=2 face=Tahoma><span style='font-size:
10.0pt;font-family:Tahoma'> Synth-diy [mailto:<a
href="mailto:synth-diy-bounces@synth-diy.org" target="_blank">synth-diy-bounces@synth-diy.org</a>]
<b><span style='font-weight:bold'>On Behalf Of </span></b>David G Dixon<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, August 30, 2019 9:05
PM<br>
<b><span style='font-weight:bold'>To:</span></b> <a
href="mailto:synth-diy@synth-diy.org" target="_blank">synth-diy@synth-diy.org</a><br>
<b><span style='font-weight:bold'>Subject:</span></b> [sdiy] vocoder filters</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=3 face="Times New Roman"><span style='font-size:12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Hey SDIY
Team!</span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>I’m thinking
about building a vocoder, and I have a general question about the bandpass
filters.</span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>I’ve looked
at Jurgen Haible’s Living Vocoder, and he used 8-pole filters with low Q.
These give a reasonably broad band with fairly steep slopes. He makes the
filters from two pairs of LP and HP.</span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>I was
thinking about using BP filter sections, but just 4-pole, and with higher Q
(around 10). This gives a somewhat narrower band, and the slope is steep
near the corner, but fairly shallow around the skirt. This idea uses a
lot fewer components (about half as many).</span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>What I’m
asking is, does anybody here have any insight into what the “proper” approach
to vocoder filters would be? What is the design goal? Do you want
significant overlap from one band to the next, or should they be fairly
distinct? I guess I’m just looking for some general guidelines and
conventional wisdom.</span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> </span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Cheers,</span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Dave Dixon</span></font><o:p></o:p></p>
</div>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>_______________________________________________<br>
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