a friend, ham radio op and commercial radio tech, suggested that solid state amps are
"cleaner" than tube amps. is that "generally" true?
There are several reasons why a tube amplifier is more likely to be
cleaner than a solid state amplifier. Most tube amplifiers have higher Q
output matching (pi or pi-L) networks than solid state amplifiers, which
generally have broadband ferrite core transformers followed by fairly
wide bandpass filters. So when properly tuned a tube amplifier is likely
to generate less noise at frequencies far removed from the intended
signal. Also the ferrite cores in the output coupling transformers and
bandpass filters in a solid state amplifier can be driven into a
nonlinear mode. An air core inductor (in most tube amplifier tank
circuits) will not go nonlinear. In general a solid state amplifier uses
more transistors to get the same amount of power, than the number of
tubes used in a tube amplifier. It is easier to keep one or two tubes
biased properly, than four or eight or more RF power transistors which
may have have slightly different characteristics. And the required bias
of transistors is more sensitive to temperature than tube bias is.
Having said all that, a well designed solid state amp should have all
those possible problems worked out, and be nearly as clean as a tube amp.
DE N6KB
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