"Trevor Wilson" wrote


snip magazine reviews and personal OSAFs


When examining the frequency response plots of the SET amps we can see
serious, highly audible flaws. When examining the distortion plots, we
can see serious audible flaws in most models at realistic listening
powers. Examining the plots of the other amplifiers, we can see no
obviously audible flaws. Choosing a SET amp over a push pull amp, is
therefore the deliberate choice of audible problems. Those audible
problems are completely artificial artefacts, not present in the
original sources.


Your problems are not everybody's problems - choice of a SET is to
choose an amp for its characteristics. The bit you can't choke down is
that people buying/choosing/using SET amps consider those
characteristics to be beneficial. Three members of the 'St Neots Six'
(local enthusiasts) own and use SETS, one of the others prefers my SET
to my PP amps, another would like a SET and the last one keeps
threatening to build one but probably never will as he is getting
perhaps a bit to old for more building - otherwise that could easily
become a *100%* instance of SETs here!!



The choice of such an amplifier is, therefore, a rejection of the
musician's/producer's philosophy.


Which is what?


The SET owner may be better off using a
'blameless' amplifier, with some tone controls and a little additional
distortion and noise.


Or he could just use a SET and be done with all that crap....



Whilst not stated in the graphs, we also need to understand what
constitutes a *proper* amplifier. A proper amplifier is the *ideal*
source. IOW: It neither adds, nor subtracts anything to the music.
Fundamentally, a SET fails this simple test very early on. Most
amplifiers are rated for XX Watts @ 8 Ohms. Fine, as far as it goes,
but the ideal amplifier will be rated for XX Volts output. IOW: It
will maintain XX Volts, regardless of load impedance. Or, to put it
another way: An ideal amplifier, rated for 100 Watts @ 8 Ohms, will
deliver 200 Watts @ 4 Ohms, 400 Watts @ 2 Ohms and so on. Naturally,
in the real world, this is an impossibility. However, some amplifiers
do come pretty close, provided saturation effects are taken into
account. For example, if we examine a typical, quality, push pull
amplifier, rated at 100 Watts @ 8 Ohms. The same amplifier might,
typically, deliver 150 Watts @ 4 Ohms and 175 Watts @ 2 Ohms. This
allows for a choice of speakers and, as the vast majority of
loudspeakers do not exhibit a perfectly resistive impedance
characteristic, is a darned good idea.


Funnily enough, all that came out when Chinese Willy was here the other
day - another instance of where fine theory falls on its arse in the
real world...



A SET amplifier, OTOH, might be rated for (say) 10 Watts @ 8 Ohms.
It's 4 Ohm power, therefore, be less than 5 Watts. It's 2 Ohm power
will be less than 2.5 Watts. It is the complete and almost perfect
antithesis of a theoretically ideal amplifier. An ok choice, IF you
happen to be using a perfectly resistive load. For anything else
(particularly ESLs), it is the worst possible choice.

SETs are a fashion statement. They're not serious high fidelity
products. Their promoters are, at best, deluded. At worst, cynical
opportunists.


Who TF's promoting them? - I only defend my preference for them. If you
or anybody else don't like and doesn't want a SET amp then fine, don't
have one...