Tubes... what do they do?...

I really mean it...

What is it that tubes do, say for instance in a Preamp or Amp..

What exactly does the tube do, what is/are it(s) function(s).. and how does it acomplish it..

It is the equivalent of the transistor in your solid-state device. It takes a music signal and amplifies it. It is what makes the amplifier amplify. For the how-do-the-work part, yes, do check out the articles posted above.
It above referanced link is an older one but still just about the best introduction. It is a bit funny, the writer spends so much time talking about how out-dated tubes are and then, at the very end, he retreats...just a bit.
"Tubes, what do they do?"

Warm your room and your soul! :-)

Sorry, I couldn't resist.
They replaced transistors.
I would say it is a matter of taste what different types of amplification moves you. I would say tubes lends a small degree of realism to the reproduced music. You can mention that you have a tube stereo to average individuals and you will be looked as an excrentic, until you play some music.
It produced this warm, soothing glow that takes your mind off of the cares of life, and your system, as it ever so gracefully distorts the signal to its final output. Not exactly what you would call a tube fan, but I have done some research conducted by independent sources and historical periodicals. Once you understand what you are reading as far as charts, specs, and graph; and apply this to to the overall effect of the systems performance, you come to this same conclusion.

Let it be opinion completely differs from the concensus of this thread and its contributors, and doesn't represent the opinion of audiogon. :)
Transistor amps generally have a very linear transfer function (until they clip). Transistor amps generally have a more 'S' shaped transfer function meaning that for low amplitudes, the gain is higher and for higher amplitudes, the gain tapers off. This can give the impression of more low level detail.
Some strange comments here.

Vacuum tubes are amplification devices, and tubes like the 243 or 300B are the most linear open loop amplification devices known to man. The proof of this is that you actually get vacuum tube power amplifiers that do not make use of any form of negative feedback, and those that do, use very little NFB.

Transistors have very high open loop distortion levels, which need be addressed by using negative feedback loops. The use of negative feedback (in both vacuum tube and transistor) in amplifier lowers distortion levels.

Opinions differ pertaining to the use of negative feedback, as it does introduce non-harmonic (i.e. phase) distortion, which many folks find disturbing. Distortions associated with vacuum tube amplifiers (with little to no negative feedback) are mostly a diminishing amounts of first, second and third harmonic distortions which many find pleasing to the ear.

Harmonics occur naturally with all sound waves i.e. strum a single guitar string and the other vibrate in harmony; so an amplifier with a high level of harmonic distortion can still sound extremely lifelike and real (because it is). Phase and inter-modulation distortion do not occur naturally, so even very small amounts can give the music a cold or hard edge and sound very unnatural.

Good amplifiers (and bad amplifiers) can be had using either vacuum tube or transistors. Anybody that simply dismisses one topology as being bad or distorted is simply demonstrating ignorance.

So Pauly...what testing results or guidelines do you use or suggest one should use to determine the difference between a good tube amp and bad tube amp? How should one inteprete the tangible results of the testings?
11-16-06: Cdwallace “what testing results or guidelines do you use or suggest one should use to determine the difference between a good tube amp and bad tube amp?”

Use the most complex and most accurate audio evaluation devices known to man - your ears.

As a bit of an education, have a look at Arthur is somewhat opinionated, but has a wealth of knowledge and experience and you may just end up learning something.
Thanks Paul. I also found this doc to be useful as well, back when I wanted to research the anatomy and function of a typical SET amp. This also includes many of the scientific strategies and practical analysis of the tube amp, which also produces tangible conclusive results.

I must admit, even though I'm not a fan of tube amplification, this document was very eductional regarding the practical applications many of today's tube amp manufactors use to test their products before release to the market.

This is just one of many available. I'll see if I can find more and post them.

I'm glad to see there is more than one person who is into education regardless of how much experience one has.

Good looking out Pauly! : )

Its amazing whats available on Google.

Check out the link below:
Here's another good link to review.

This covers both arguments, so to speak.
Don't wanna be a pest about things but here's another.
CD Wallace – apologies for my tone in prior post, it was uncalled for.

The article you posted pertaining to the CAD300SEI is spot on. I always cringe when folks want to show me test results to prove how good their sound is … my ears have rarely been able to match their test results.

The hobby wouldn’t be much fun if there wasn’t things to learn.

Slightly off topic. I spoke to a gent name Peter Ledermann of Soundsmith ( . He has just developed a brand new type of electro mechanical cart that does not make use of coils or magnets. If what he says is true, it will be a paradigm shift for analogue folks … Yep, there a lot to learn and a lot of new things audio.

"my ears have rarely been able to match their test results."

It is important to learn this skill, because the measurements are the sound, with the exception of small nuances. Knowing what measurement effects which part of the sound can really help cut through lots of options and help you "upgrade" you system with much more control and direction.

What is dangerous about measurements is it sets a standard that people can make objective judgements about the performance of equipment, and this is very bad for high end audio. Once you can take your own measurements it becomes very easy to correlate the general performance of a product and what is sounds like. The imperfection of measurements is only human, what we interpret and how we take them.

Information is information, its how you sort it out that makes it useful or not. Whether you hear the information (can't print it out) or see the information

PS: tabulated measuremnts like ".0004% distortion", absolutely useless agreed there. The battery of graphs on Stereophile reviews super useful, even when JA changes the measurement tolerance to make a product look good.
Eddie, you really don't comprehend english well at all ... were making such progress until your last post. What happened?
CDWallace – Not sure what you consider “progress”, but I doubt I was leaning towards what you consider progress. After 30 years in this hobby I do still learn a lot, but most certainly not from just anybody.

What I have learned though is that facetiousness and irony is lost on some, and in a big way. Anybody following the thread would know my statement “my ears have rarely been able to match their test results.” is obviously tongue-in-cheek … well almost anybody.

I recall many years back watching a flamenco guitarist tune his guitar with an electronic tuner. I recall thinking that he probably wouldn’t be much of a musician if he couldn’t tune by ear. I was right; he was pathetic.

Same holds for an audiophile. An audiophile who cannot trust his ears is not worth listening to.


I think CDW was refferring to the fact that you made a post that did not directly insult or belittle someone to make your point.

Can you tune a guitar by ear pauly?

Your attempt at humor fell short, as I believe it would be against your nature to place those who measure equal to yourself a true music lover.

But since you are part of the measurmeent brigade! Maybe you can tell us about your speakers and amplifier and how they measure and how that relates to what you actually hear. I would be very interested with what someone with all your experience and knowledge has to share. Sharing some of your 45 years of experience would be appreciated.

What kind of speakers do you have again? Do you use the new ETF or Liberty, Mlssa?