Tube Watts vs. Solid State Watts - Any credence?

The effect has to do with the distortion of the amplifier.

Since a transistor amp clips harshly, its obvious when it happens. A tube amp has a soft clipping characteristic (which can be modified somewhat depending on how feedback is used with the amp). So even though the amp is overloading, as it enters clipping it won't **sound** like it- and as you push it harder, the higher ordered harmonics become more abundant. Since the human ear uses those harmonics to figure out how loud a sound is, their presence will make the amp sound louder than it really is. This works until the clipping is so severe that the amp starts to break up and makes hard clipping like a transistor amp.

If you place a sound pressure level meter in the room, the phenomena will be revealed, which is to say that watts is watts.

I should have written that sentence differently pointing out that output power depends on the topology of the tube - triode vs. ultra-linear vs. pentode with the output power going progressively higher as one moves from triode to pentode.

Really it depends on how many tubes are used. Our MA-3 makes over 500 watts and its entirely triode, yet the H/K Citation 2 is pentode and only makes 60 watts. I think what you were trying to say in this passage is that pentodes **usually** pack a lot more power per tube than triodes usually do (there are triodes out there that make a lot of power; more than most pentodes).

Ultra-linear is a means of approaching triode linearity while retaining the power output of a tetrode or pentode (either can be used in ultralinear). The use of tetrodes, pentodes, triodes and ultralinear operation otherwise has nothing to do with power at all.

i think he's saying the same thing Atma-sphere & I & others have already written which is: a watt is a watt but each amp reacts differently with each speaker.

Actually I was more commenting on strictly how the amps distort- tubes interact favorably with human physiology while generally transistors do not (lower ordered harmonics as opposed to the dreaded 7th harmonic). This interaction can be quite profound and hard to turn down when you hear it!

A few years ago my band was at a show in Chicago. There were a lot of bands on the bill and to save time with each one shifting gear on stage, we offered to 'backline' our bass amplifier- a 400-watt Peavey ('backlining' is the process of having some equipment left on stage that all the bands would use during the show). One of the bands had a 500-watt Orange bass amplifier, which is class D. He wanted the extra power. He was quite blown away when I pointed out that a class D 500 watt amplifier would in no way keep up with a 400 watt tube amp on stage. He tried it and agreed- but had to go back to the class D amp as the Peavey made far more bass energy than he was used to- he was used to the thinner sound of the class D amp and was a little panicked that he would not be able to get the right sound (they were going on first).

Geoffkait's dynamic headroom theory falls apart when faced with a class A amplifier, which can be either tube or solid state.

The Dynamic headroom of an amplifier is measured in decibels, and has to do with the class of operation and the amount of energy storage in the power supply. The spec is rarely used today. The more dynamic headroom, the poorer the amp in general; the idea being that if class AB and without much power supply, for a brief instant the amp will be able to make more undistorted power than its constant power spec.

A Class A amplifier will have 0 db of dynamic headroom. A really bad amp will have 3 db of dynamic headroom. The spec was created in the 1970s to make cheap amplifiers look good on paper.

To be more specific, my tube amp has a 1040 joule power supply. In my "un-technical" way, I interpret that as "head room" because my amp presumably can handle short term power demands that exceed its rated power output of 150 wpc, subject to FR, speaker impedance and tap output impedance. Am I mixing and matching terms and concepts here??

Yes.

Its important to understand that the concept of 'dynamic headroom' and the resulting spec was entirely 100% marketing on the part of the manufacturers of inexpensive amps and recievers during the 1970s.

A worse amplifier has higher dynamic range? Worse how?

I did explain that in my prior post, here it is again: the amp has a small power supply that will not allow it to operate at full power continuously. On top of that, it would probably overheat if it did due to poor heatsinks. Further, it is biased class AB and likely exiting the A region with less than 1/2 watt output. These properties will allow the amp to put out brief spikes of power that otherwise its design does not allow in a steady state condition. The higher the headroom number (in db) the cheaper the amp.

Class D FWIW is not an exception to this rule of thumb- the best class D amps will make about the same power whether continuously or not.

Gee, in all this time on this thread no one has bothered to mention the most distinguishing feature of tube amps vs solid state amps. That is the lack of the irritating harmonics present in solid state amps.

Actually I did allude to that earlier...

Mapman, while there are some solid state amps that have less of the 7th harmonic that has become the hallmark of transistor amplification, there are none that are at the low level that tube amps often demonstrate, although I think there are a few that come close.

Class D is no exception, at least not with any of the amps I have heard and own. Their artifact does seem different than the traditional transistor type; so far it seems that no-one can make an amplifier that is truly neutral.

If you really want an amplifier that is as smooth as a tube amp you are going to have to get a tube amp (its the lack of the 7th harmonic that makes them smooth). If you want to avoid that 2nd harmonic that makes tubes so lush you have to avoid amplifiers that employ single-ended circuits.

The EL34 has a very good reputation in the sound department. A lot depends on how well the ultra-linear taps on the transformer are executed; if done correctly the linearity is just about the same as triode so my vote is for the EL34 in ultralinear mode, assuming the transformer is designed correctly.

Tube amps using ultra-linear mode of operation use a lot of global negative feedback to generate a higher wattage.

Bombaywalla, taken either in or out of context its hard to take this comment seriously. I've modified many Dyna ST-70s where the only feedback was the ultralinear operation itself and the amps worked fine. But the real problem with this statement is you can't apply feedback to get greater power. If the amp is capable of greater power is something entirely independent of feedback.

"Output stage coupling is a combination of “ultralinear” and Audio Research’s patented “partially cathode-coupled” topology, which is superior to conventional pentode or triode operation."

Its funny to me that they got a patent on that since Leslie amplifiers (of Hammond organ fame) had used the same technique in the 1950s.

I'm not even treading into the realm of "is 14dB too much global negative feedback?"!! ;-)

14 db is an 'inbetween' figure which normally leads to *increased* distortions of some harmonics, but as others have said the ARCs use other forms of feedback as well- ultralinear being one, and the cathode cross-coupling being another. If neither technique were used 14 db would very likely be problematic.

tube amps have no bass hence it's power mostly applied towards mids and highs while the solid state amps go full range.

As prediceted, I take umbridge with this remark as it really is simply false. Our amps make full power to 1 or 2Hz depending on the model. But what is really going on here is that most box speakers don't have decreasing impedance as frequency goes down; while many have dual woofers arrays, they will also have an impedance peak that is part of the resonance of the drivers in the box. So if you have a 4 ohm tap you can likely make that work on a tube amp.

More importantly is the question of whether that's even a good idea, as every amplifier technology known has audibly higher distortion when driving lower impedances. I've yet to encounter a good reason for increasing amplifier distortion if sound quality is the goal!!

well some of them isn't most of them. it's nature of tubes and output transformers. they're weak when impedance of speaker goes down on low frequencies.

This statement is false. First- tubes are not frequency-dependent devices and often have bandwidth far in excess of most semiconductors. The design of the output transformer is the real variable- its no problem designing one that will do quite well in the bass. The trick is doing that and getting the highs right at the same time.

Yes, a watt is a watt, but, the way most tube manufacturers measure their gear, a tube watt is, arguably, LESS than a solid state watt because tube manufacturers typically spec the output at a much higher allowed distortion level.

This statement is misleading. The way both solid state and tube amplifier manufacturers do it is with **the onset of clipping**. Many tube amplifiers will have higher THD at the onset of clipping than solid state amps might. FWIW that THD is usually of lower-ordered harmonics that the ear finds to be musical, whereas solid state amps are far more likely to have much higher levels of the 7th harmonic, which the ear finds to be really objectionable. Hence the tube/transistor debate over half a century after tubes were declared 'obsolete' and yet the tubes are still here.

And if you are thinking 'well all we have to do is build a solid state amp that doesn't make any 7th and it will sound as smooth as tubes' you would be nearly correct, so have at it!! The best designers out there (Nelson Pass, John Curl, Charlie Hanson) are all aware of this fact and have been for a long time. Its no coincidence that they have designed some of the best sounding transistor amps made.