Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!newstop!eastapps!vergil!gsteckel
From: gsteckel@vergil.East.Sun.COM (Geoff Steckel - Sun BOS Hardware CONTRACTOR)
Newsgroups: sci.electronics
Subject: Re: How do I choose a capacitor type ?
Summary: tweaks don't use polyester
Keywords: distortion capacitors
Message-ID: <4193@eastapps.East.Sun.COM>
Date: 5 Feb 91 20:13:49 GMT
References: <64@owl.ukc.ac.uk> <1991Feb5.185727.14775@news.larc.nasa.gov>
Sender: news@East.Sun.COM
Reply-To: gsteckel@east.sun.com (Geoff Steckel - Sun BOS Hardware CONTRACTOR)
Organization: Omnivore Technology, Newton, Mass. (617)969-3448
Lines: 27

In article <1991Feb5.185727.14775@news.larc.nasa.gov> kludge@grissom.larc.nasa.gov ( Scott Dorsey) writes:
 In article <64@owl.ukc.ac.uk> abs@ukc.ac.uk (A.B.Smith) writes:
 >I am currently building a number of audio circuits (pre-amps, effect
 >boxes, that sort of thing) and the circuits I have don't specify the
 >construction material of the capacitor.
 
- For coupling capacitors in audio circuits (DC blocking caps), use polyester
- or polypropylene caps.

The `true believers' in audio wonderfulness would never use a polyester cap
anywhere.  In fact, they do have a large `dissipation factor' and apparently
are somewhat nonlinear, as are `high-K' ceramics (with Z5U or Y5V tempco
markings).

I would recommend polystyrene or polypropylene film caps for wonderful coupling
caps, or low-K (NPO) ceramic or mica caps for small values ( < 100 pF).
They will be much larger physically and cost much more than the polyester caps.

I don't think this distinction applies for bypass (shunting unwanted signals to
ground).  I'd use polyester for bypass type applications.  A common trick is
to bypass an electrolytic with a film capacitor of 1-10% the electrolytic's
value to achieve good high frequency performance for bypass applications.
Cost & size vs. religion is the tradeoff in this case.
	geoff steckel (gwes@wjh12.harvard.EDU)
			(...!husc6!wjh12!omnivore!gws)
Disclaimer: I am not affiliated with Sun Microsystems, despite the From: line.
This posting is entirely the author's responsibility.