[Boatanchors] Yet another tube question

[Glen Zook]

The question was about tubes used in final amplifiers
of transmitters and not audio circuits.  Most audio
applications use push-pull circuits where matching can
make a difference.  With a very few exceptions final
amplifier tubes are run in parallel and not push-pull.
 The Heathkit VHF-1 Seneca is an exception in that it
does use a pair of 6146 tubes in push-pull.  Of course
there are a number of VHF and UHF transmitters that do
use dual tetrode tubes that the sections are in
push-pull but those are single envelope tubes and
using "matched tubes" is not a possibility.

Even in audio applications many people are just not
capable of "hearing" the difference between tubes that
are matched and those that are not matched.  There are
individuals that are able to actually "hear" the
difference but in many "real world" applications the
difference is shown by test equipment and not by ear. 
Of course if one tube is extremely weak and the other
brand new there definitely will be a difference.  But
when both tubes are generally in the same condition
when put into service many people will not be able to
notice any difference in performance.

Glen, K9STH



--- Ron <ronami at yahoo.com> wrote:

I disagree with Glen's views, so let me present the
'other  side'. 
 
To be honest, my own background involves high end
audio amplifiers, where most of the time, the answer
is in the affirmative. 
 
Anyone that needs more than a pair or two and has the
equipment, can save some money by ordering a bunch of
devices and selecting the most closely matched pairs.
This is what I do.









Glen, K9STH

Website:  http://k9sth.com


 
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