Tube Watts vs. Solid State Watts - Any credence?

Kijanki is very right---a hard clipping amp is dangerous to the health of your tweeters. I had a low-powered SS amp burn out a dome tweeter in the blink of an eye when it clipped, and the volume was pretty low.

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.

So a followup question - if 2 amps both have 140 watts, why ever buy the more expensive amp if you are paying for wattage? Most have indicated quantity of wattage, but can the quality of wattage be better in some amps than others? Secondly, how can low powered tube amps sound so much better with some speakers that have amp recommendations much higher? Very few tubes get over 100 watts, yet are very prevalent even on some inefficient speakers. Any thoughts? Just trying to learn more.

I am using a pair of 40w EL34 monos driving a pair of 87dB efficient bookshelves full range with a sub crossed over low just to augment what my speakers can't reproduce and it rocks....plenty of power in my 15 x 17 x 9 room

I had previously used a McCormack DNA 125 which was a great amp no doubt but I don't think I even came close to it's full power even at louder volumes

Do

That's like saying why ever buy the more expensive tv if they are both 52 inch. Or the more expensive car if both have same horsepower engine.

With technology no single spec ever tells the whole story. In fact specs as a whole cannot. No two amps are exactly the same. There many differences some subtle and some profound. Quality being just one general category. Same as with any complex piece of technology.