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<DIV dir=ltr align=left><SPAN class=214295109-16022022>For my application, I
needed to go down to 0.1Hz. For this, I found 22uF to be adequate, so two
47uF caps.</SPAN></DIV><BR>
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<FONT size=2 face=Tahoma><B>From:</B> Synth-diy
[mailto:synth-diy-bounces@synth-diy.org] <B>On Behalf Of </B>Tom
Wiltshire<BR><B>Sent:</B> Wednesday, February 16, 2022 1:31 AM<BR><B>To:</B>
Brian Willoughby<BR><B>Cc:</B> Synth DIY<BR><B>Subject:</B> Re: [sdiy] emulating
bi-polar capacitors<BR></FONT><BR></DIV>
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Non-UBC Email]</FONT></TD></TR></TBODY></TABLE>Why do we need such large
capacitance values anyway for DC blocking caps? Is everyone feeding low
impedance loads and trying to reproduce sub-bass signals?
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<DIV>Putting 100K/100n into 1/2PiRC gives 15Hz, and you can easily go two
octaves lower (220n, 470n) with standard film caps, or reduce impedance
accordingly.</DIV>
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<BLOCKQUOTE type="cite">
<DIV>On 16 Feb 2022, at 06:30, Brian Willoughby <<A
href="mailto:brianw@audiobanshee.com">brianw@audiobanshee.com</A>>
wrote:</DIV><BR class=Apple-interchange-newline>
<DIV><SPAN
style="TEXT-TRANSFORM: none; FONT-STYLE: normal; TEXT-INDENT: 0px; DISPLAY: inline !important; FONT-FAMILY: Helvetica; WHITE-SPACE: normal; FLOAT: none; LETTER-SPACING: normal; FONT-SIZE: 12px; FONT-WEIGHT: normal; WORD-SPACING: 0px; TEXT-DECORATION: none; caret-color: rgb(0, 0, 0); font-variant-caps: normal; -webkit-text-stroke-width: 0px">While
writing firmware for a digital mixer, the folks over in the
digital-controlled-analog-preamp team discovered distortion that was traced to
the polarized capacitors. I did not look at the schematic, so I don't know
what the exact problem was. They changed the capacitors for the next prototype
and got rid of the distortion. I don't remember whether they switched to
bi-polar caps or just found polar caps with a higher voltage rating. I seem to
recall it was the latter, but it stuck in my mind that the electrolytics could
cause distortion due to their polarized nature - at least for large input
signals and/or high gain settings.</SPAN><BR
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style="TEXT-TRANSFORM: none; FONT-STYLE: normal; TEXT-INDENT: 0px; DISPLAY: inline !important; FONT-FAMILY: Helvetica; WHITE-SPACE: normal; FLOAT: none; LETTER-SPACING: normal; FONT-SIZE: 12px; FONT-WEIGHT: normal; WORD-SPACING: 0px; TEXT-DECORATION: none; caret-color: rgb(0, 0, 0); font-variant-caps: normal; -webkit-text-stroke-width: 0px">Sorry
for the non-answer. Seems like there's definitely the potential for problems
that can't be ignored, but the solution is not necessarily bi-polar.</SPAN><BR
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Feb 15, 2022, at 12:30, Mattias Rickardsson wrote:</SPAN><BR
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<BLOCKQUOTE
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type="cite">Hej Danjel and others,<BR><BR>I don't recall seeing any hard
facts about non-polarized electrolytics performing better than ordinary
polarized in audio circuits, but still they occasionally turn up in designs.
Would be interesting to hear why they sometimes are preferred by audio
designers, though! :-)<BR><BR>I searched for "non-polarized" in Douglas
Self's reference book "Small Signal Audio Design" and found a couple of
applications where they actually do make sense - but it's a practical reason
rather than an audio performance reason:<BR>DC blocking in inputs &
outputs, where it's possible that the connected gear pulls the voltage way
off ground level, and you never know in what direction.<BR>Douglas Self
writes:<BR><BR>"C2 is a DC-blocking capacitor to prevent voltages from
ill-conceived source equipment getting into the circuitry. It is a
non-polarized type as voltages from the outside world are of unpredictable
polarity, and it is rated at not less than 35 V so that even if it gets
connected to defective direct-coupled equipment with an op-amp output jammed
hard against one of the supply rails, no harm will result."<BR><BR>Any other
good reasons for using them?<BR>And sorry, no - I don't have any better
advice than what has already been said. :-)<BR><BR>/mr<BR><BR>
<BLOCKQUOTE type="cite">On Feb 15, 2022, at 11:32 AM, Mike Bryant
wrote:<BR>
<BLOCKQUOTE type="cite">I've never bothered, I've never noticed a
difference in just using a 47ì instead of playing about with
back-to-back capacitors even after the thick end of 40 years the
earliest stuff I built that way still has capacitors that capacitate
just fine.<BR></BLOCKQUOTE>--<BR>
<BLOCKQUOTE type="cite">Gordonjcp<BR></BLOCKQUOTE><BR>Agreed. Unless
you actually have a reverse DC bias voltage (in which case rotate the
capacitor) I've never understood any need for the non-polarised
capacitors. Most mixing consoles are full of thousands of them
either feeding the input or fed from the output of an opamp via a resistor
to ground.<BR><BR></BLOCKQUOTE></BLOCKQUOTE><BR
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