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wrote:

I guess the peers were
also tubies. Either that or they were smokin' some gooooood stuff. Maybe
both. ;-)
I'd like to find some AES old-timers and get some straight answers about how
a POS like the Hamm paper made it through the JAES review process. The
guilty parties are probably dead and gone by now, so the truth might be
knowable despite the confidentiality of the review process.

Has anyone here actually READ The Hamm article. It woiuld appear
not, as it does NOT support any of the assertions made about.
Consider the precis of the article:

"Engineers and musicians have long debated the question of
tube sound versus transistor sound. Previous attempts to
measure this difference have always assumed linear operation
of the test amplifier. This conventional method of frequency
response, distortion, and noise measurement has shown that
no significant difference exists. This paper, however, points out
that amplifiers are often severely overloaded by signal transients
(THD 30%). Under this condition there is a major difference in
the harmonic distortion components of the amplified signal, with
tubes, transistors, and operational amplifiers separating into
distinct groups"

Let's look at the KEY points of the article:

* Previous attempts to measure this difference have always
assumed linear operation ...

* amplifiers are often severely overloaded by signal transients
(THD 30%).

The article ONLY deals with the amplifiers topologies AT THE TIME,
UNDER CONDITIONS OF SEVERE CLIPPING DISTRTION.

It makes NO claims about the operation under normal conditions.
The implications are quite clear: Clipping results in audibly
different
output from. An early 1970's tube amplifier sounds different than an
early 1970's transistor amplifier WHEN BOTH ARE BEING SEVERELY
CLIPPED SUCH THAT THEY ARE GENERATING 30% THD.

The solution to the problem is NOT to by tubes or transistors. The
answer to the problem is VERY simple:

DON'T CLIP THE AMPLIFIER!

Thus, Hamm's paper supports the reasonable assertion that a 250
watt sollid stats amplifier MUST sound better than a 20 watt tube
aplifier when both are being asked to try to produce more than 20
watts.

"Don't clip the amplifier" is easy to say, and tough to do. Totally
avoiding amplifier clipping under any and all circumstnaces requires
either active power compression control (i.e. "Power Guard") or a
really, really, really big amplifier, the very small signal performance
of which is usually suspect unless the amplifier is made extremely
heavy and hot and has a very high quiescent power draw. A 20 watt tube
amp that pulls 50 watts at full power is more efficient in practice
than a 250 watt solid state amp that pulls 80 watts quiescent and 500
at full power if either provides the same _subjective_ performance-even
though the solid state amp is more efficent for each watt it puts out.

Thus, Mr. Ludwig's assertions:

"Subjectively tube amps of a given specification often (not always)
sound better than solid state amps of better spec. Russ Hamm
proved it in 1973 with his paper which appeared in JAES"

is simply not supportable. The ONLY difference that the Hamm paper
deals with is under conditions of sever clipping, which is not
"always,"
it's not even "often" as Mr. Ludwig erroneously claims. Further, his
statement:

"and it has not been contradicted."

Is similarily false, as the following citation suggest:

Monteith, Jr., Dwight O.; Flowers, Richard R.; Hamm, Russell O,
"Transistors Can Sound Better Than Tubes," Vol 25, no. 3,
pp. 116-120; March 1977

What's interesting is Hamm, the author of the paper erroneously
cited by Ludwig, is one of the authors of this paper!

Further, the suggestion by Mr. Krueger that there is something
fundamentally amiss with the article or the reviewers is similarily
off the mark, because if you actually deal with the contents of the
article, you find that it makes reaonable sense: solid state amplifiers
clip differently than tube amplifiers, and for a variety of reasons.

First, Hamm's article by title states "transistors _can_ sound better
than tubes", which is sometimes true, not that they "always do" which
we know to be false.

Either vacuum tubes or trnasistors can be used with good results.
However many people still prefer to use vacuum tubes, at least under
certain circumstances.

However, I have not yet read this second Hamm paper, and will endeavor
to do so. It still won't make building tube amps any less
recreationally rewarding, though.