[Irwin]

I'll be the first to admit I have very limited knowledge of things electronic.If I've read it once, I've read it a hundred times,many claim that there's more power to  Tube watts than Solid State watts.I understand that Tubes and SS have different sonic signatures,but isn't
a watt a watt?Educate me.

[JohnR]

I think that what is meant there is that a 25 watt (say) tube amp sounds subjectively louder than a 25 watt solid state amp, because the tube amp can be driven further into compression/clipping before it becomes objectionable.

Whether that is actually true or not, I don't know, never tried to verify it Presumably the circuit topology of the specific amps would have a lot to do with it.

[Folsom]

There are a lot of factors involved in that. How hard certain things are to drive, input impedance, level of gain, etc...

Also the more distortion or anything going on wrong with solid state makes it require more volume to reveal more, in my experience, but it never seems that loud. That is my experience anyhow.

[Wayner]

In my book, a watt is a watt. However, speakers are not purely resistive loads. Also as JohnR stated, the tubes seam to buffer a clip a bit nicer than a SS amp might. I do think that unless you have very efficient speakers, this lower wattage is just not desirable. Unless your a SET guy of course, then 25 watts is overkill.

Wayner

[Niteshade]

I agree that a watt is a watt. Here's the thing: If you have a tube & SS amp rated for 100 watts each, they should both become overdriven past or at 100 watts. This is why these specifications are written- so you know where breakup (over-modulation) occurs.

[BillB]

I think class plays a big part in it too as a pure class A amp seems to play "bigger" than an AB of the same wattage.

[macrojack]

In my personal experience tube amplifiers always have seemed more powerful than similarly rated SS units. However, I put this topic out of my mind a few years ago by going to high efficiency speakers.
So far I have not been able to figure out why everyone else hasn't done so. Is there a reason?

[darrenyeats]

Valves do not suddenly clip when overdriven, they have a soft area where the music is compressed. This is less obvious than clipping by an overdriven solid state amp.

Of course, compressed signal does sound louder - i.e. has a higher average level - than the equivalent uncompressed signal with the same peak level. That's why valve amps might sound louder than the equivalent SS, but it only happens when the valve amp is pushed into a zone where compression happens.

Compression in general can have a seductive quality to it, depending on the music. It can bring out details which might be lost in noise (recording or system noise floor, environmental noise etc). But it is of course undesirable if dynamic range and low distortion is your aim.
Darren

[Philistine]

Below is a recommendation for Salk HT3's:

50 - 200 tube watts
120 -300 solid state watts

Tells me that Jim considers SS and Tube watts are not the same?
Or are other parameters involved? 

[bunnyma357]

Beyond tubes sounding better when driven to distortion I think SS watts also include mainstream brands that overrate their power specs, testing with not all channels driven. Many receivers won't do well with 4 ohm loads or lower and will go into protection mode and shutdown. So some people when saying tube watts are more powerful may be talking actual usable watts vs. maximum marketing watts.

Jim C

[planet10]

Valves do not suddenly clip when overdriven, they have a soft area where the music is compressed. This is less obvious than clipping by an overdriven solid state amp.

that is a generalization. One can make a tube amp that clips just as hard as a typical SS amp (ie fully differential Class A triode with CCS on the output pair cathodes).

How an amplifier recovers from overload also affects the apparent power availability.

dave

[darrenyeats]

Below is a recommendation for Salk HT3's:

50 - 200 tube watts
120 -300 solid state watts

Tells me that Jim considers SS and Tube watts are not the same?
Or are other parameters involved? 

These figures are a guide not a fixed range. The point is to create a sound with realistic loudness and realistic dynamic range in your room with these speakers. Tastes and rooms vary hence the ranges. Why are the ranges different? Every speaker has limits as to continous power handling and peak power handling.

With valve amps the average power of the output can increase (without obvious clipping) as gain increases past the point at which the peak signal reaches the peak rated power. Note the average power increases but the peak power does not, much - this is compression. But effectively, the average power is put on steroids.

With SS amps the average power of the output cannot increase (without peaks clipping obviously, harshly and dangerously for the speakers) past the gain at which the peak signal reaches peak rated power. On the bright side the relationship between average and peak power is maintained by this restriction - this means uncompressed signal. Anyway, you can't put an SS amp's average power on steroids.

That's why 200W=300W.
Darren

PS: As for speakers which present harsh loads, this will bring out the above effects all the more quickly because the power demands are increased (peak rated power arrives at a lower gain). Of course speakers with harsh loads tend to be speakers with passive crossovers. This problem as well as a host of others are mitigated with active loudspeakers, and actives are my recommendation to anyone starting from scratch...

[doak]

The difference in power delivery of SS as compared to tube power derives from the stored energy in the power supply. 
It is true that quality SS amps have much larger PS caps than tube amps, so how then can tube amps be so superior at instant power delivery?  The answer is in the formula for stored capacitive energy:  .5 x C x V squared = Stored Energy.  Here's the key: SS amps operate at a rail voltage of around 60-80 volts.  Tube amps may operate at 600 volts. The voltage squared of the SS amp (60x60) equals 3600.  The voltage squared of the tube amp is 360,000.  Makes a BIG difference in the calculation - by a factor of up to 100X!  It way more than makes up for the smaller caps in the tube amp PS and in instant energy reserve/delivery.    (credit to David Manley in the "The Vacuum Tube Logic Book" for first making me aware of this important fact).

Doak

[TerryO]

As I've mentioned on other forums, the output transformers used in tube amps and especially SET amps have a real problem with erratic impedance curves. If the curve has a relatively smooth curve the tube amp is actually capable of extended bass as much as an octave (1/2 octave is entirely possible) beyond what a typical SS amp can provide.

The fact that tubes can provide extended bass at a low level may, due to Fletcher-Munson effects, cause the Tube amp to actually sound louder.

As for a watt is a watt, it depends on the current and the impedance load. This, is perhaps another reason why tubes sound so powerful as well. It certainly has motivated Nelson Pass to attempt to achieve with SS, what a good tube amp is capable of. His "First Watt" designs are single stage, single ended Transconductance modeled a on SET Tube topography. He attempts to get by with as little Negative feedback as possible (SE Triodes are the most linear device ever created and need miniscule amounts, or no negative feedback) and has seen improved sound as a result.

Without getting into negative feedback, damping factor and THD, I can only say that much of the thinking has changed among designers in the last few years with a lot of the common knowledge of yesteryear being really out of date.

Best Regards,
TerryO

[Browntrout]

I think tubes are better at amplifying music full stop. They sound more realistic, more like real music.
   One Watt will always measure as one Watt but what it actually physically is, what causes the current can be very different from one amplifier to another and be changed by something as simple as different diameter wires or material used.
   When you look at the time component of  current and therefore power it can be seen to be dependant upon electron availability. In other words as current is measured as a certain number of electrons passing a point the more electrons that are available per cross sectional area of the conductor the faster that current can be provided.
   An Amp in one device could be produced by 0.5 Coulombs of charge moving distance x or by 1 coulomb of charge moving 0.5x. This affects power as it will take (all other things being equal) twice as long to create the current in the first instance as you have half as many electrons moving twice the distance compared to the second example ( please note the figures are just for example).
   The measured results as far as Watts are concerned will be the same but the physical occurance in the conductors is different.

[darrenyeats]

I think tubes are better at amplifying music full stop.

I can't argue with that. Personally, I think that if a source or amp has acceptable levels of distortion, bandwidth and frequency response, what you think about that piece of equipment can make more of a difference to your enjoyment than the equipment itself!
Darren

[Browntrout]

It's not what I think about the equipment it's what I think about the sound that the equipment makes.