[sdiy] emulating bi-polar capacitors

[Danjel van Tijn / intellijel]

Hey Mattias,

What method are you usually using for eliminating DC offset between opamp
stages?  Do you use polarized electrolytics? Or some other strategy?



On Tue, Feb 15, 2022 at 12:37 PM Mattias Rickardsson <mr at analogue.org>
wrote:

> Hej Danjel and others,
>
> 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! :-)
>
> 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:
> 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.
> Douglas Self writes:
>
> "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."
>
> Any other good reasons for using them?
> And sorry, no - I don't have any better advice than what has already been
> said. :-)
>
> /mr
>
>
> Den tis 15 feb. 2022 20:43Barry Klein via Synth-diy <
> synth-diy at synth-diy.org> skrev:
>
>> I used one in a typical dual op amp triangle oscillator on the phaser in
>> a Music Man amp design. It made a difference in extremely slow sweep
>> symmetry and also I had a function where you pull the knob out and could
>> fix the sweep wherever you wanted it. After I left the whole thing was
>> redesigned. Maybe I didn’t know what I was doing….  45 years ago…
>> Self-taught by Electronotes. What a fun job before work politics F’d it all
>> up.
>>
>> Barry
>>
>>
>> > On Feb 15, 2022, at 11:32 AM, Mike Bryant <mbryant at futurehorizons.com>
>> wrote:
>> >
>> > 
>> >> I've never bothered, I've never noticed a difference in just using a
>> 47μ 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.
>> >
>> > --
>> >> Gordonjcp
>> >
>> >
>> > 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.
>> >
>> >
>> > _______________________________________________
>> > Synth-diy mailing list
>> > Synth-diy at synth-diy.org
>> > http://synth-diy.org/mailman/listinfo/synth-diy
>> > Selling or trading? Use marketplace at synth-diy.org
>>
>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
>> Selling or trading? Use marketplace at synth-diy.org
>>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20220215/ff40dfaf/attachment.htm>