Tube
Renaissance
Tube Renaissance
A possible expalnation of why tubes may sound
better than transistors.
From the late 1960’s, tubes were largely,
though not entirely, superceded by semiconduc-
tors in audio frequency amplifier designs. This
was an inevitable consequence of a continuing
quest
for
new
techniques.
Semiconductors
(Transistors and Integrated Circuits) have cer-
tain and obvious advantages: their small size,
absence of heaters, low voltage operation and
consequent opportunity to dispense with output
transformers may appear to make tubes obso-
lete. However, from about 1975 onward, there
has been a resurgence of interest in tubes; and it
seems worthwhile to consider why.
It is said by ‘hi-fi’ enthusiasts that tube
amplifiers sound better, that their distortion is
either lower or less noticable. Carefully con-
ducted listening tests seem to bear this out,
although their results are difficult to interpret. If
there really are subjective differences to a
listener between tubes and semiconductor am-
plifiers, can they be explained technically?
One thing should be clearly understood: it is
possible to design either a tube or a semicon-
ductor amplifier so that over a certain range
of output power its distortion will be so small
as to be imperceptable to the ear. Therefore,
if two similarly rated well-designed high
fidelity amplifiers, one using tubes and the
other using semiconductors, are compared in
the same listening conditions, correctly oper-
ated, their performance should be indistin-
guishable - and subjectively perfect.
Now, on the basis of measured performance,
many modern high fidelity semiconductor
amplifiers are actually superior to the older
tube amplifiers, which were already good
enough for their distortion tobe impercept-
able; so how can here be subjective differ-
ences? It seems that there cannot be any,
while the amplifiers are correctly operated:
and this may be the key to the mystery, for
there are two major problems: one is that it is
extremely difficult to avoid occasional over
driving of an amplifer, because of the very
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