Who will survive? One last table til I die.

Dear TWL and Teres:

With respect to the answer given by Mr. Crabbe, he's right when he says that the voice-coil impedance can be considered to be in series with the amplifier's output impedance. However, that's not the point. The ideal amplifier's mission is to work as a perfect voltage source, regardless of the load impedance presented at its output terminals. This ideal can be reasonably approximated using many technologies -vacuum tubes, bipolar transistors, mosfet transistors, etc.- However, using vacuum tubes this task is almost unsurmountable, simply because tube 99.9% of current designs depend heavily on the use of an output transformer that further introduces anomalies, distortions, colorations, saturations, phase shiftings, etc. etc. By the way, perhaps at this moment the word OTL will come to your mind, but I could mention many aggravations they have too, but that is another matter that would be subject of a different thread. Anyway, assuming that all these problems could be solved, tubes generate big amounts of harmonic content not present in the original signals, and I see this as the biggest obstacle in our road to true fidelity. Tubes will always add sweetness to the music, at the expense of accuracy, that to many music lovers as myself means fidelity. Today's solid state devices, on the other hand, have current linearity far more linear and and noise characteristics far more desirable, all in favor of a better musical experience. This is the ultimate goal of listening to music.

And regarding Teres arguments, I have several points I would like him to consider: Tubes are voltage devices, whereas transistors are current devices. Therefore they operate in completely different fashions, not similar. Any electronics designer can confirm that. Although tubes and transistors both present big amounts of distortion if not corrected, transistors have the advantage of having complementary devices, that when properly matched, can virtually eliminate alinearities, harmonic distortion and IM distortion without needing any global feedback. Unfortunately, there are not and will never exist such thing as a complementary tube; they simply can't have this fundamental advantage. So when you say that transistors depend on big amounts of feedback, I can see that you have been simply ignoring the state-of the-art in modern solid-state design, where non-feedback is almost a gospel.

Ultimately, there will never be such thing as a zero-feedback amplifying device, and this includes single-ended triodes (where the electron flow and the space charge are the feedback parameters working in conjunction with the grid-cathode voltage) and transistor emitter-follower configuration (where the flow of minority carriers is the feedback parameter). I agree that a zero-feedback amplifier would be great, but it's not achievable yet.

Regards and enjoy the music,

Raul

"The ideal amplifier's mission is to work as a perfect voltage source, regardless of the load impedance presented at its output terminals"...

"Tubes are voltage devices, whereas transistors are current devices."

Is this an inadvertent mistake or a blatant inconsistency?

"Tubes will always add sweetness to the music, at the expense of accuracy, that to many music lovers as myself means fidelity."

The truth is that distortions of tubes is much less objectional to the human ear becasue it is a "natural device" God is a much better designer than man will ever be. Raul you confuse confuse the absence of euphonic colorations(some disingenuous solid state designers have added that distortion in order to compete with tubes.)with accuracy. The fact is that transistors have added a cold sterile quality to the sound either by adding or taking away something from the music. It reminds of the argument that a vpi motor was noisy and that could be proved by listenig to a tunrtble with a magnetic bearing. Shouldn't we be comparing motors.

..."using vacuum tubes this task is almost unsurmountable" You previously said "impossible". So we are making some progress.

Those of us who have been around for awhile remember that using amplifer specs as a means of evaluation is more of a madison avenue ploy than science. It was an attempt to convince us that transistors must be better than tubes because they measure better.
Raul as indeed your own post which refers us to $350,000.00 amp proves. It is the ss electronics that require major trickery to cure it's inherent problems. Everytime I read about or hear a ss amp that I can live with it is priced way beyond my reach.

As a huge fan of conrad johnson I look forward to auditioning thier Premier 350. It is suppose to achieve low distortion without any feddback. Somtimes that means only no global feedback. Examination of its spec's indicate it does not "double down" like Krell. I have nothing against ss per se.
Enjoy the music and playing with your equipment!(stereo) Thanks to all you guys for whetting my appettite for stereo again. Pardon me while I earn some money to buy some equipment!

Anybody notice how Raul's English improved about an order of magnitude in that last post? Interesting...

Raul, I do agree that there are some favorable characteristics to both SS and tube designs.

However, it appears that you are attempting to engage in some kind of "specs race" between SS and tube amps. Distortion Specs are only useful in some regards, and are not indicators of performance in a music system. The methods used to measure them are not the same as the intended use of musical playing, and therefore may have little or no bearing on the actual musical performance of the amplifier. Static sine-wave distortion measurements into a dummy load are not even close to the way an amp produces music. Most informed users do not rely on these specifications. The ear can hear distortions produced by a design that do not show up in any measurement protocol.

Regarding "complementary transistors", they are only applicable in Class AB or B amplifiers(push-pull), which require switching, phase-splitting, or both, and are not the equal of true Class A design(no phase-splitting or switching) for musical reproduction. But I agree that complementary Class AB is nice to use when you need a high power amp that cannot run totally in Class A all the time, for use with certain difficult speakers. But it is obvious that virtually all Class AB SS amp makers bias them as high as possible, to keep the amp in Class A as much as possible. This is simply a "de facto" example that any kind of Class B(complementary or not) cannot compete with Class A sonics of a similar quality level amplifier(maybe even from the same manufacturer). They just do this switching to Class B so they can output more power without as much wasted heat. Not for better sonic performance than Class A.

Regarding your comments on "unwanted harmonic content", which I suppose means "harmonic distortion", you only have to look at harmonic distortion curves of various amplifier designs to see that SS amplifiers have relatively low amplitude harmonic distortion characteristics, but have them all the way up the spectrum, and have them primarily in odd-order content, which makes them much more objectionable to the ear, and therefore they have to be lower to be even listenable. Tube amps, on the other hand, especially Single-Ended Triode amps, have a somewhat higher amplitude harmonic distortion curve, but it is located primarily(almost completely with SET) at the 2nd harmonic interval, and is almost all even-order distortion which is easier on the ear, and also easier to deal with by other aspects of design. Push-pull tube amps are not as good in this regard as SET, and suffer from both odd and even order harmonic distortion, as well as the phase-splitting and complementary amplification things. But they can be good sounding amps nonetheless, if they are designed and built well(typically with some negative feedback that was well applied).

Regarding your discussion about output transformers, this is the crux of your previous discussion that included output impedance of tube amps and their performance with reactive speakers. The tubes have higher output impedances than transistors, and usually must have impedance-matching output transformers to achieve a low enough output impedance to drive a speaker load. This is well-known. I agree that there are problems associated with output transformers. However, very good output transformers achieve a very high level of performance, and mitigate the problems to a large degree. OTL and ZOTL can eliminate these output transformers, but traditional OTL must resort to parallel-ganging of the output tubes to reduce the output impedance to a useful level(which is still usually a bit too high, but works), and only ZOTL allows the use of true SET Class A single-tube output, with impedance matching to the speaker that is under 2 ohms,no output transformers, and devoid of the typical transformer artifacts. As you know, this is a unique circuit from David Berning, and it the circuit used in my personal amplifier. The distortion from this(my personal) amplifier has total harmonic distortion of much less than 2% in the audio spectrum and the predominating location is at the 2nd harmonic(with much much less in the rest of the spectrum). Output impedance with 0 feedback is under 1.8 ohms. The circuit is true Class A(no phase split) and has a single output triode per channel, which negates any need for any "complementary devices". Bandwidth extends to 500khz. It can produce a square-wave anywhere in the audio range. True full-power bandwith is produced down to 2Hz(where a coupling cap intercedes to avoid DC), and this produces very prodigious and fast bass response. Signal-to-noise ratio is better than -100db(quieter than most SS amps). Supersonic(RF)frequencies are used to heat the tubes, for heater noise elimination and long tube life. The amp is 12vdc powered to eliminate line noise. It has choke-loading for improved linearity. Super short signal path. Ultrahigh-speed switching power supply that is very stiff. Overall, this amp is about the most advanced and most musical amplifier that I have ever heard or seen, and it is a tube amp. I realize that specs are not the answer, as I mentioned earlier, but if you want some specs, there they are.

If you want to quibble about the 2% total harmonic distortion spec on my amp, then it would be useful to note that the single-driver speakers that I use have a similar 2% harmonic distortion profile at the 2nd harmonic primarily, and the judicious connection of the speakers at 180 degree phase angle to the amp outputs cancels much of the overall system harmonic distortion, and results in an overall system distortion much lower than any competing SS or tube amp with multi-driver speakers( which have wide ranging additive distortion profiles and cannot benefit from this happy matching). See the articles by amp designer Eduard de Lima on SET amps and single-driver loudspeakers, available with a web search.

I have no "axe to grind" against SS amps in general, and there can be some very nice SS amps. I have owned and heard many. My main purpose for my posting here, is to rebut the premise that you have made, which states that tube amps cannot be serious musical amplifiers. I hope I have done that. Nothing is perfect. Bliss is in the ears of the beholder.

Dear Twl:*****" The distortion from this(my personal) amplifier has total harmonic distortion of much less than 2% in the audio spectrum and the predominating location is at the 2nd harmonic(with much much less in the rest of the spectrum). Output impedance with 0 feedback is under 1.8 ohms. "****

This is exactly the point: THD 2% is really a high distortion it does not matters if location is: 2nd harmonic. But the output impedance of 1.8 OHms is a heavy problem for your amp can works like a constant voltaje source ( it's almost imposible ). This very high output impedance is the problem.
Now, you can check in your Stereophile's any ( all ) of the tests about, for tube and SS amplifiers,. and you can find the terrible errors that have all the tube amplifiers when they are trying to match the impedance of the speakers. Again, you can hear it.
Gregadd,this is not how it measure it is that any one can hear that big mistakes. The output impedance in the tubes amplifiers, usually, goes from 0.5 to 3 OHms ( high one ) and the output impedance in the SS goes from 0.02 to 0.5 OHms ( very low one. That's is one of the parameters why the SS has a high damping factor ). This is the point and the problem on the subject and you can hear it ( any one ).
BTW, I'm not in love with " specifications numbers " but like in the cartridge/tonearm combo is very important the " number " on the resonance frecuency, here at the amps this output impedance is one of the issues.
Any one that is using tube amplifiers in their system, don't really know how really " sound " their speakers and don't know the true performance of their audio system.
Don't say " NO " for what I'm telling you, till you do a serious test with a whole SS audio system at your home and for at least three months.
Regards and enjoy the music.
Raul.
Regards and enjoy the music.
Raul.