tube watts vs transistor watts?

There's lots of informative answers here but I'm not sure they have answered the original question.

When an SS amp approaches its power rating, it will go into distortion very, very quickly. Suppose it is rated at 200 watts; then if you try to get 210 watts out of it, you could easily get 10% THD or more. It will sound totally horrible. So in practice, you would not actually want to go anywhere near 200 watts with such an amp, because the power level of a music signal varies greatly and you are just asking for trouble.

On the other hand, the tube amp rated at those same 200 watts (this would be a little beast btw) can go to 210 watts and the THD might not go a whole lot higher than 1%.

So it's not so much that the tube amp is more powerful than its rating, but rather that the SS amp is not as powerful as its rating (by comparison); that's how I think of it.

That, and the realization that 30 watts is a whole lot louder than we think. :)

Stanwal, I went to the Stereophile website and randomly selected a solid-state amp reviewed there (since they have nice graphs in their review). Ok, not so randomly selected--it was at the top of the list and it's probably the most recently reviewed. :)

It's an Electrocompaniet AW400. Looks like a reasonably nice amp, $12,500 (pair of monoblocks). Look at the graph on Atkinson's measurement of power output, Figure 3. The curves do exactly what I said: slow decrease in THD with rising power, until suddenly they hit a barrier and spike drastically upwards.

You might say that SS amps have a dramatic change in the second derivative of their power vs. THD graphs right around their rated output, compared to tube amps. That very different approach to distortion results in the effects that we've been talking about.

So tube amps and SS amps are different beasts when it comes to power ratings, and it is quite valid to make a correction accordingly. A rule of thumb I've seen here and there is that N watts of tube amp is about the same as 3N watts of SS amp, because of this effect.

Now if you can make absolutely, positively certain that your SS amp will never distort as the signal level routinely approaches that boundary, then you can change that rule of thumb accordingly--but that's a toughie.

Tvad, I'm sure you know everything I posted here (ever). You *probably* meant "maximum" instead of "minimum", but that wasn't what I was getting at. It's not just that we humans like one kind of distortion better than another. Whereas for tube amps, the line into "too much distortion" is somewhat arbitrary (1% THD? Why not 5%? 0.1%?), for SS amps, it's much more straightforward: they are either pretty linear, or catastrophic.

When I listen to Mahler's 3rd with the tube amp, I occasionally sigh or smile when the little guy runs out of gas, since it's not so bad and what are you going to do. When I turn on the 275 watt SS beast, I get the symphony in its proper loudness... with a finger right on the remote ready to stop the thing. Living dangerously.

Re-reading the OP again, maybe he was just asking if his speakers would blow up? Man, don't worry, if you can afford a 200 watt tube amp, you can afford new speakers. :)

Stanwal, aside from snide disrespectful remarks, did you bother to look at the graph at the Stereophile site that I told you about?
I'm sorry that you have to take that tone, it suggests you have other problems.
Now do go to that graph, then come back and tell us what precisely you see in that graph that motivates you to show so much contempt.