tubes, transistors......

[Magnus Danielson]

>>>>> "EB" == Eric Barbour <ebarbour at svetlana.com> writes:

Hi Eric and all you others!

 >> 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.

 EB> Sorry if you were annoyed by my comments, Magnus. The main issue
 EB> here is that I constantly hear these incorrect statements about tubes,
 EB> repeated over and over again.

Let me stress that I was only annoyed about the more flamish or
flamish-like parts. I certainly don't mind you making a point about
that tubes are good, and can you prove it then the better.

 EB> Their 3/2-power response is not the
 EB> problem--the problem is with the actual signal distortion in-circuit,
 EB> using a standard class-A amplifier circuit. Load-lines do not follow
 EB> the 3/2 curves, and it's the load line that determines the input-output
 EB> voltage gain equation of a device. (Nor does the load line of a bipolar
 EB> transistor follow an exponential response. The SPACING of the device
 EB> curves determines its linearity.)

Well, I must confes that I haven't spent too much time study up on the
subject, but I do have spent some time and will continue to do so.

The 3/2 curve is the transconductance behavior just as the exponential
curve for bipolars are.

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

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

 EB> Often I find myself answering these comments. They are
 EB> made very often, by electrical engineers and marketing gurus
 EB> who think they know why these "crazy audiophiles" prefer tubes.
 EB> They always miss the point!

I think I understand this point you are making, but then I find that
this category mostly misses the point so... It is certainly an most
anoying thing. Some of the tube-heads that I have met have how ever
also missed the point or at least been babeling about so much rubbish
that listening to it all just became anoying. This is BTW true for
many non-tube people too. If you happend to find my 1st of April fool
from last year (on AH) I think you can get my feeling about it.
But I think that the kind of people hanging around on this list falls
into a diffrent category and thus could be treated in a diffrent way.

 EB> Distortion spectra are only PART of the reason for using tubes,
 EB> and only then as a sound effect. Too many smart people like
 EB> to make ignorant generalizations, which are then repeated by
 EB> ordinary people as if they were hard facts. That's what happened here.

This problem one has to fight every day. What MAY be true in one
special case migth not be true in another not to say a general
case. Hell, it might not be true in the special case it is being said
to hold for. Today I found that yeat another generalisation that a few
of my companies EEs made did not hold, so tomorrow we will fix it
behind their backs in order to save money and time... most anoying.

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

Well, it seems that (in my eyes) you tended to use formulations
indicating that you more or less been heading this way. I would even
say that I seen strong tendenses, and I don't want to see that.

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

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

Eh, I where more refering to that I mentally blinded myself for the
comments you made, in order not to accidentally fall into flamewar mode.
My comment where pointing towards the fact that they where trapish.

 >> 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. 

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

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

It is certainly true that NP-junctions have a voltage-variable effect,
it is a very nonlinear effect. The high negative feedback (I think you
are refering to the Miller effect) is also there. One thing that
people tend to do wrong with bipolars is to use them as both voltage
and current amplifiers in the same time, high-current transistors
should be left away from voltage amplification to perform well. I have
seen power amps built this way work well.

The understanding of transients and their effect is as much black
magic as many other things to many people. When one care about
transient responce (regardless of technique in use) will much better
performance manifest itself than if you just strive for that
ultra-flatt frequency response. This is certainly true for large PAs
as well as a home setup, I have done both.

However, when I see how people go about and destroy their impulse
responses with all kinds of stuff (like most of the speakers out
there) will the empere's new cables or whatever just be a change of an
screwed up behaviour rather than an actual fix.

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

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

It is easy to "prove" something, it is far less easy to do it in a
scientifically way such that it will survive the critical eye and
other test. There is also many diffrent sides to things, often one
sees how people tries to show something where they infact showed
something else and through vague bridges (often postulates that can be
found untrue with some minor knowledge) the try to prove some fact.

I will not get into discussion weither Dan Dugan did so or not.

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

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

This thread is not a nice one, but I think we have touched a few other
subjects which could be enlightening to continue on.

As for the IEEE Spectrum article, at least I will look forward to see it.

Cheers,
Magnus