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.
