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From: bblue@crash.CTS.COM (Bill Blue)
Newsgroups: rec.audio,sci.electronics
Subject: Re: I really ***HATE*** electrolytic capacitors
Message-ID: <1520@crash.CTS.COM>
Date: Wed, 12-Aug-87 19:01:43 EDT
Article-I.D.: crash.1520
Posted: Wed Aug 12 19:01:43 1987
Date-Received: Sat, 15-Aug-87 05:55:18 EDT
References: <3646@sdcsvax.UCSD.EDU> <3650@sdcsvax.UCSD.EDU>
Reply-To: bblue@crash.CTS.COM (Bill Blue)
Distribution: na
Organization: Crash TS, El Cajon, CA
Lines: 77
Keywords: capacitor flame wars
Xref: mnetor rec.audio:2792 sci.electronics:1157

In article <3650@sdcsvax.UCSD.EDU> brian@sdcsvax.UCSD.EDU (Brian Kantor) writes:
>>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....

Electrolytics in the audio path are awful.  There's no if's and's or
but's about it.  In many many cases they are much larger than they
need to be -- it all depends on the load impedance that they feed.  
Some simple r/c calculations can be made to determine applicability of
lower value non-electrolytics.  In many cases a 5 or 10mf polyprop
or wonder cap is more than sufficient for linear response to below
10hz.  Electrolytic bypasses are generally ok, if they are bypassed with
.01's and .1's of reasonable quality.  Electrolytics (and tantalums) as
dc blocking in an audio circuit are just flat unacceptable.  

>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.

You *don't* want inductance or any kind of leakage in any of these
applications.  

>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.

Golden or not, even untrained listeners will readily appreciate 
improvements made by proper component selection.  It really matters
how much you enjoy audio.  If it's just background music it really
doesn't matter a whole lot.  And of course, the better the circuitry
design the more evident these types of changes will make.

>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.

Certainly it's good to be selective with any replacement components,
but besides the gross differences described above, a great many of the
characteristics that make an audio component sound good aren't
measurable by methods readily available.

Probably one of the most overlooked areas in audio equipment improvement
programs is the power supply.  Invariably, it will be extremely anemic
and irregular in its frequency response (actually impedance curve).  
Dramatic improvements can be made in this area with relatively minor
changes.

--Bill