Why Cap Value Spread

Questions and Answers

From postmaste--(at)--riodeel.com Thu Jul 29 20:07:07 CDT 1999
From: postmaste--(at)--riodeel.com (Ned Carlson)
Newsgroups: rec.audio.tubes
Subject: Re: Random Question/History of Component Values
Date: 29 Jul 1999 19:56:08 -0500
Reply-To: postmaste--(at)--riodeel.com
Xref: geraldo.cc.utexas.edu rec.audio.tubes:130888

On Tue, 27 Jul 1999 23:45:36 -0700, david--(at)--umnet.ucla.edu (David A.
Anderson) wrote:

>
>Hi,
>
>I've been wondering about this for a while, so I've decided to reveal my
>ignorance and ask why typical component values have shifted over the last
>30 years?
>
>For example, lot of the older gear I work with has capacitor values of
>5uF, 25uF, 50uF, but now, you find capacitors at 4.7uF, 22uF, and 47uF.

It maximizes the use of inventory if the values are such that the
tolerances (usually 10%, but long time ago 20% was common) just
slightly overlap.
If you've got 20% tolerance, instead of the old values of .01, .012,
015, .02, .025, .03, .035, .04 and .05, you get .01, .015, .022,
.033, and .047.
See, right there we've ditched 4 items off the inventory, and forced
all the engineers to pick 20% parts whether they like it or not ;-)
The Pointy Haired Boss would be proud of us.


Ned Carlson Triode Electronics "where da tubes are!"
2225 W Roscoe Chicago, IL, 60618 USA
ph 773-871-7459 fax 773-871-7938
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