John Atkinson wrote:

I have been following this thread and I don't think those who talk
about the Wavac amplifier "clipping" at 2W can have read the
review (it's now available in the www.stereophile.com archives). If
you look at the graphs of output power vs THD+N percentage, you will
see that it does indeed put out 2W at 1% THD+N, which is our usual
definition of "clipping." However, it is important to note that the
Wavac is _not_ clipping at this level of distortion.

I looked at the graphs. I think you need to redefine your definition
of clipping. Clipping is when the distortion products (when viewed on a
scope with a nulled out fundamental) show the beginnings of an apparent
spike, which happens as an output device reaches saturation (or cutoff)
on signal peaks.


What happens is that as the output power increases, the waveform
becomes increasingly asymmetrical, meaning that the signal
increasingly suffers from second-harmoic distortion. While this
is indeed audible once the Wavac is putting out a watt or so, it
doesn't sound like clipping distortion, particularly as it is not
accompanied by catastrophic amounts of intermodulation distortion.

But it results in lots of effectively audible IM with music signals
as opposed to test tones. Some people like this, but I don't.


As I wrote in the review, true waveform clipping occurs at a few
tens of watts, depending on the output tap and load. So for anyone
to cast aspersions at Michael Fremer's hearing ability because he
didn't hear "clipping" is inappropriate, given the particular
nature of the Wavac's non-linear transfer function.

I have no doubt of his ability to hear what he likes. What is
questionable is his ability (probably from lack of training and/or
interest) to identify defects that legitimately bother many/most
others. I can't speak for anybody else, but I just don't like these
kinds of amplifiers.


When I listened to the Wavac, the bass boost was immediately
apparent, but it didn't sound aggressively distorted. Partly
this is because the amount of power typically demanded from an
amplifier tends to be below 2W much of the time with music rather
than test tones; partly this is because second harmonic distortion
tends to fatten the sound in rather a pleasing manner, at least
until the intermodulation products reach threshold.

It can also introduce dynamic effects that aren't in the original
signal. Some folks like this, others don't. Why do a lot of pop
musicians prefer to use compressors and expanders in their recordings?
I can't stand them because I prefer acoustic music. If someone likes
it, that's fine with them, no?


Please note that I am not defending this amplifier's performance.
I am only pointing out that those on this forum who condemn its
sound without actually having heard it are shooting in the dark.

Not really.

It's performance is actually fairly typical of single ended tube amplifiers,
(you likely know this, since you've tested some of them) but it has more
power than most because of the use of a large transmitting tube for the
finals. There's no mystery about this. It's simply a matter of a person
just liking (or not) this kind of amplifier. Most probably don't.

The 'rating' of 150W is vulgar, grossly deceptive and a joke by any
modestly reasonable standard.