Final Tube question

[Glen Zook]

None of the major manufacturers including Heath and
Collins ever shipped a new transmitter with "matched
pairs".  Frankly, all that matching really does is to
increase the price and the profit of the company that
is selling them.

Now when tubes are used in push-pull and not parallel
(virtually all of the boat anchor rigs use the tubes
in parallel) and push-pull is used usually in audio
circuits, there may be a very slight advantage to
using matched pairs.  However, even in most audio
applications the "average" person cannot tell the
difference.

Most tubes "age" at different rates and even if you
start with matched pairs in a relatively short period
of time they are no longer matched anyway.  

Now you generally don't want to put a very used tube
in with a brand new tube.  However, if the tubes are
basically the same age (by age I mean in time used)
they will work fine in at least 99.999 times out of
100.  The 0.001 time is going to be when one of the
tubes is defective.  You generally replace all of the
tubes in the final amplifier section at one time.  If
not, you want to observe them for a little while to
make sure that the "new" tube isn't handling more
power than the other one (look for red on the plates,
etc.).

If you haven't read the article on the 6146 family of
tubes that was in Electric Radio a while back, and has
been published in several other publications as well,
go to either of the websites that are listed at the
end of this message.  You will find the article on
either site.

Glen, K9STH


--- "TChesek at Epix.Net" <tchesek at EPIX.NET> wrote:

Many Heath rigs use a parallel final output tube
configuration. Often times I see "matched" tube sets
for sale for 6146, 6GE5, etc. Are there technical
reasons, other than power output, to match these or
doesn't it matter?









Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco

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