tubes, transistors......

[Eric Barbour]

>Saying that tubes are non-linear to some degree (as he did) is not
>much of a fallacy, but you are also right in that you may get a
>wonderfully linear response from them as well.

Sorry if you were annoyed by my comments, Magnus. The main issue
here is that I constantly hear these incorrect statements about tubes,
repeated over and over again. Their 3/2-power response is not the
problem--the problem is with the actual signal distortion in-circuit,
using a standard class-A amplifier circuit. Load-lines do not follow
the 3/2 curves, and it's the load line that determines the input-output
voltage gain equation of a device. (Nor does the load line of a bipolar
transistor follow an exponential response. The SPACING of the device
curves determines its linearity.)

Even an average 6SN7 triode can beat the PANTS off any transistor
operating at typical low voltages, in a simple distortion test.
As we at VACUUM TUBE VALLEY magazine discovered.

The guy who made the original comment was just repeating something
he read. It's not his fault.

Often I find myself answering these comments. They are
made very often, by electrical engineers and marketing gurus
who think they know why these "crazy audiophiles" prefer tubes.
They always miss the point!
Distortion spectra are only PART of the reason for using tubes,
and only then as a sound effect. Too many smart people like
to make ignorant generalizations, which are then repeated by
ordinary people as if they were hard facts. That's what happened here.

I am NOT trying to start flames. So everyone, please calm down.

> EB> 	I CAN PROVE IT!!! Any takers? 
>Eric, I did NOT see those lines, do you know why?

The information was not posted here, because it will shortly
appear in IEEE SPECTRUM magazine........that ought to be
authoritative enough to be taken more seriously than stuff like
this, off the PAIA website, written by John Simonton:

>One by one these squashing characteristics have been removed.
>The first improvement was transistors. It's difficult and expensive to make tube
>circuitry linear, they just really don't want to do it. Individual transistors
>are no more linear than tubes, but they're cheap so you can afford to use
>lots of them..................................When loafing along within their design
>envelopes, there is no discernible difference between SS and VT amplifiers.
>This has been shown again and again in well designed double blind tests. 

The whole text is at http://www.paia.com/tubesnd.htm.

As much respect as I have for John Simonton, I feel compelled to point out
that he is WRONG here. There are other sonic effects inherent in solid-state
electronics--voltage-variable capacitances, slew-rate limiting, high negative
feedback and its effects, etc. These effects are TRANSIENT,
and do not show up in static distortion tests, nor do they become very apparent
in some A-B listening tests.
These transient effects are nonexistent or less apparent in tubes.

"It's difficult and expensive to make tube circuitry linear, they just really don't want to do it."
Sorry, John, you have a LOT to learn. It's not as simple as that.

And there are a few tube/transistor A-B listening tests in the literature--unfortunately,
they were often biased, because the people running them had an agenda
to accomplish. (One of the most notorious "tests" was run by Dan Dugan in the AES Journal
some years ago--it is still often quoted by the uninformed, even though Dugan was heavily
criticized at the time for not allowing the listeners longer selections, and for being domineering
and aggressive in his methods. Dugan is a notorious "skeptic" who has a blatant
anti-tube bias. It's really funny--I happen to know that he services Nagra equipment
as part of his business; Nagra recently introduced a very expensive TUBE amplifier
and preamp......... )

A major objection to these tests, by respected academics such as
Dr. James Boyk at Caltech, is that such tests allow only a few seconds
of listening for each device, rather than allowing the listeners to control the
musical material and length. This has only made the tube-using
audiophiles bolder, and roiled the waters further.

Let's put an end to this thread, it has very little to do with synths anyway.
I'll end with a suggestion for any interested parties to read the SPECTRUM article.
It is scheduled to appear in the upcoming August 1998 issue.