How do tube Watts compare to SS Watts?

The amplifier power will also depend on the room size, and your listning position distance from the speakers.

I use a PrimaLuna Prologue 2 ( 45 Watts KT-88 Valve Integrated, close to US $ 1K ).

Speakers are Sonus Fabor Extremas. Same sensitivity as your speakers.

Room size is approx 30 feet x 15 feet x 12 feet height.

Speakers & listning position is accross the width ( 15 feet ) of the room, not the length.

My listning position is approx 10 feet from the speakers.

I get good volume ( my gusstimate is 103 dB ) before the the amp runs out of steam.

I would HIGHLY recommend the PrimaLuna Prologue-2 if you listen to Rock and Jazz. The Prologue 1 with EL-34 valves is probably better for classical.

Hope this helps.

Cheers

I powered a pair of Vandersteen Model 3 speakers with Quicksilver tube M-60 amps ( rated at 60 watts ) During that time I did a demo with a CJ MF2300 ( rated at 200 watts ) I could not hear a significant difference other than a bit more bass. I was under the influence that when comparing watts " tubes to ss " you doubled the rating for tubes.

60 watts tubes would be equal to 120 watts ss.

I would say that 80-120 watts would be necessary in your case though.

Rascal, the most important factor when using a tube amplifier to drive speakers, is that the speakers must have a benign impedance curve. If the speakers have an impedance curve that varies significantly, even a 1000-watt tube amp will have problems driving them. The nominal impedance numbers i.e. 4 ohm or 8 ohm is not really important as most tube amps have 4ohm and 8ohm output taps.

In short, if your Thiels do not have a benign impedance curve, go solid state.

I drive 88db speakers to very loud levels with a 12wpc amplifier, so in theory you should be able to do the same with and amplifier rated around 20wpc. Again I repeat, this will hold only if your speaker has a benign impedance curve.

There is definitely something different between the rated output of a tube amplifier and a transistor amp. Wattage is measured the same, that much is true, but anybody that has compared tube and transistor based amps of similar ratings will be well aware that the vacuum tube amplifier can produce much higher SP levels before overloading is detected.

This is partially due to the fact that tube amplifier clip in a harmonic (musical) fashion, while high NFB used in transistor amps make them square off the signal when clipping. This squaring off of the overload is very noticeable and objectionable. As such, transistor amplifiers cannot be run near their maximum rated output. Tube amplifier can.

Another theory I have heard is that naturally dispersed harmonics add to the perceived SP of the signals. Vacuum tube amplifiers tend to produce high levels of naturally dispersed near maximum output. Transistor amplifiers tend to produce unnaturally dispersed harmonics which are both very objectionable and add nothing to the perceived SP levels. Tube amplifiers therefore deliver a bit more than what their rating suggests.

Regards
Paul

Yes, a watt is a watt is a watt but the rail voltages on tube amps are much higher. In my expereience comparing tube wattage to solid state wattage it is about a 2 to 1 ratio.

1 SS watt = 2+ tube watts in my experience in terms of filling a space with sound.