tube Watts vs solid state Watts


Hi folks, can anyone explain to me why 20W tube amp is more powerful than a 20W solid state amp? Further: a 20W pure class A amp is more powerful than a 20W class B amp. Why is that? I've always thought Watt = Watt.

Chris
dazzdax
No doubt the tube amps I have owned play louder and have more "power" then higher rated (watts) SS amps. Very much my experience. My current 45 watts monblock tube amps have more speaker driving power then all 50 - 100 watt SS amps I have owned. I have owned many good ones to be sure.

My experience confirms this on many, but not all of the tube amps I have owned. It depends on the builder. Some tube amps are spec'd at 50 watts and only put out 32 when measured. Other tube amps put out more then the stated power.

The same is true for SS mps. I owned an Aloia 60 watt amp that was measured to put out 100 watts. Again, really depends on the builder and what they decide to list in the spec's.

However, in general, tube amps sound more powerful than like wattage SS amps. This is in general.

Bill
Not all ss amps clip harshly, if at all. My CarverPro ZR1600 have clip detection and automatic gain reduction if clipping occurs. I have never seen the CLIP LED illuminate. However, in home audio application this is probably the usual case as the darned thing is rated at 600 watts into 4 ohms.
Other than the tubes vs. solid-state argument and the class A vs. class B argument, an amp with a larger power supply will often sound louder and more dynamic due to its ability to drive more current, i.e. dynamic headroom. When I was in school I learned this and was amazed at a demo at my local Circuit City. The salesman there was comparing a 26 wpc Harmon Kardon receiver versus a 90 watt Pioneer integrated amp. I and others there expected the more powerful Pioneed to blow away the HK, right? So we were all amazed to hear not only that the HK had much better sonics, it played much louder. The sales guy then asked someone to stand on a scale he brought in and the HK was twice as heavy, hence a much bigger power supply.
I suspect that part of the perception that tube watts sound louder than solid state has to do with people being deceived into thinking they need WAY more power than they actually do need.

Solid state can deliver a lot of power cheaply. So, makers of a lot of solid state gear push the benefits/need for a lot of power. Power is much harder to supply from tubes, and personally, I find most high powered tube gear sounds pretty bad.

So, when one hears a demonstration where a tube amp sounds really good while being rated at 20 watts and a 200 watt solid state amp sounds less impressive, one tends to conclude that the 20 watts of tube power sounds stronger. Actually, it is more likely to be the case that the speakers really only need a few watts, when played at normal levels, so the extra power of the solid state amp was wasted. Oversized solid state amps are particularly cheated in such demonstrations because a lot of solid state gear does not sound its best when idling along while tube gear is at its best at low output.

I see so many people argue about how much power is needed to achieve "realistic" levels, based on measurement of SPL at concerts and factoring how much power is needed to achieve peak levels. But, the simple fact is that NO commercial recordings ever deliver that full dynamic range so one never needs what "theory" supposedly dictates. I'll take great performance over the first watt of power any day over ability to deliver a lot of power for peaks that may never actually be in a recording. One watt on most speakers, even inefficient ones, is surprisingly loud.
Ok folks, so the point is here not that the tube Watts are more "powerful" than solid state Watts in absolute terms (when measured) but they are more powerful in terms of psycho acoustics. It's the subjective finding that not all Watts are the same. So when someone is saying that a 20W tube amp is more powerful than a 100W solid state amplifier you have to correct that somewhat by using abovementioned explanation.

Chris