tube Watts vs solid state Watts

While on one level a watt is just a watt, we also have to take into account how humans hear. As Duke noted early in the thread, we perceive "loudness" far more on the average level than peaks.

Take the following example with a 20 watt tube amp and a 20 watt transistor. Both are plugging along into a 87 dB efficient speaker. We're using roughly 10 watts to crank out a loud 96 - 97 dB average volume. We encounter a 3 dB peak in the music which requires doubling the needed power. Both amps deliver their maximum unclipped volume without clipping.

However, if that is a 6 dB peak, we now need 40 watts so both amps clip. The tube amp will give a better behaved clip that is less likely to draw attention to itself so we leave the volume control alone. The transistor amp clips harshly. Many people will respond to that harshness by turning the volume down until the harsh sound goes away.

This is the mechanism that causes many to say tube amps sound more powerful, watt for watt, than a transistor amp. Nothing real complicated going on.

Keep in mind that powerful transistor amps are widely available so if well matched with the speakers, this isn't a big problem these days.

As for transistors delivering more current & power as impedance drops, this only happens at certain frequencies, generally in a reasonably narrow band. You only get the extra power if your peak just happens to be composed primarily of energy at the correct frequencies. Music isn't generally composed and played with much consideration that the loud parts conform to a particular frequency profile. As such, it is a roll of the dice as to whether a transistor's extra power at lower impedances will be a benefit when playing any given piece of music.

All of that said, one is still better off buying an amp of appropriate power for your speakers and listening habits. The better solution is to avoid clipping and the need for impedance-related power all together.

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.