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From: brian@sdcsvax.UCSD.EDU (Brian Kantor)
Newsgroups: rec.audio,sci.electronics
Subject: Re: I really ***HATE*** electrolytic capacitors
Message-ID: <3650@sdcsvax.UCSD.EDU>
Date: Tue, 11-Aug-87 15:09:16 EDT
Article-I.D.: sdcsvax.3650
Posted: Tue Aug 11 15:09:16 1987
Date-Received: Thu, 13-Aug-87 05:42:55 EDT
References: <3646@sdcsvax.UCSD.EDU>
Reply-To: brian@sdcsvax.UCSD.EDU (Brian Kantor)
Distribution: na
Organization: UCSD deaf wombat society
Lines: 46
Keywords: capacitor flame wars
Xref: mnetor rec.audio:2771 sci.electronics:1148

>Really want to make it sound MUCH better? Pull all the electrolytics out of
>the preamp and power amp and put in 2 uF mylars or polyprops if you can
>find them.

Bullsh*t.  Most of the capacitors in the preamp and power amp are on
the order of 50 to 100 uF; the smallest are 4.7uF.  Replacing them with
2uF polypropylene caps is going to change the sound, that's sure
enough.  I don't think I'd want to listen to it anymore, though.  And
I've got great and glorious visions of finding a 5,000uF polypropylene
speaker coupling capacitor....

Try an experiment sometime - take your LCR bridge, feed a 10kHz
generator into it (so that it's not running at 60Hz, which many do by
default), and measure the inductance of a large-value (4 - 10 uF) mylar
capacitor.  You may find, as I did, that it's quite a bit more than the
same value tantalum electrolytic's inductance, so if you want to go
around installing low-pass filters between all the stages of your
amplifier, feel free.  Look at the dissipation factor, Q, leakage
current, etc.  Try several type, and get a feel for it.  Yes, the mylar
and polypropylene capacitors have many superior characteristics, but
they are not 100% across-the-board better.  It will, in some measure,
depend on where they are in what circuit.

True, they'll have a whole lot less leakage current than old
electrolytics, but a solidly-biased transistor stage can easily
withstand the few microamps of leakage that a new tantalum electrolytic
provides.  Remember, we're talking about old equipment here, when it
wasn't unusual for transistors to have hfe spreads of 10:1 in a single
lot.  It's Dynaco, circa 1973.  Right out of the back of the RCA
transistor manual.

I wonder how many people upgrading old equipment try replacing the old
parts with new ones first, before changing the type of the part.  I
mean, an old amplifier full of bad capacitors can't help but sound
better with new parts in it, no matter what flavor they are.  I'm not
insisting that the mylar or polypropylene capacitors don't make a
difference, I just wonder if I'll ever be able to hear it.  My ears
aren't golden by a long shot.

By the way, I tested every one of the new capacitors at 10kHz for
dissipation factor, leakage, and correct value before I put them in to
replace the old parts.  Worth it, too, since about 1/3 of the
new-off-the-shelf parts were unacceptable too.  Most of the bad ones
had ten-year-old code dates; it pays to shop carefully.

	- Brian