D-Man wrote:
I've come across that fact many times but I don't quite understand why.
How they are measured. Power is measured at onset of distortion (it's a hi-fi thing, where distortion is undesirable) and, while solid-state stay clean until the upper end of their power range, valves tend to start distorting at much lower gain levels, so are rated at much lower levels (about half) than they are actually capable of producing. Valves also compress naturally, so you sound much louder on average.
To my knowledge, a watt is a watt? How does one watt differ from another?
Specs are generally totally meaningless, at worst completely misleading. Even when they are not, you need to know how to interpret the specs to get an idea of the real-world performance of the device and for most people it's simpler just to plug in and try the damn thing... Especially as the manufacturers naturally only show you the specs that look good (you have to know how to read between the lines and look for the specs that they aren't showing you).
Watts are a perfect example - there are different "standards" for measuring them, some which are useful to the electronic savvy person (RMS), some offer a more real-world perspective (Continuous/Program) and some which are totally useless and misleading (PMPO). Even then, in a guitar amp, without also knowing the sensitivity of the speakers, you will still have no idea how loud the amp is in a playing situation.
