Understanding Tube Power Ratings

Don't be shy! Go for the tubes. I had Thiel 3.6's and ran them with older VTL 225 DeLuxe monoblocks, 225wpc, and they sounded great . . . better than I when I ran them with a Levinson 333, 300wpc. Tube power gives you "more," watt for watt, and tubes sound better.

No problem. The Rogue 99 has a 23db gain and 30V p-p which is great for any power tube amp with the Thiels. I use a 3-watt 2A3 and a 26db/50Vpp CAT with my Thiels - and it works. And, no, you're not missing anything. Whether you have a tube or a SS at 250 watts, they both can, at full volume, blow out drivers which can only handle, say, 100 watts maximum.

As to why some will say that a "tube watt" is more than a "solid state watt" is not contraindicating the laws of physics. Tube amps have higher dynamic head room than SS amps. Headroom is the ability of an amp to push out more power than rated for a brief time, which comes in handy during transients. Each 3db of headroom doubles the peak power delivery. Tube amps have headroom ratings as high as 5 to 10 db whereas SS amps can have HR less than 1 db and 2 db is typical. The best SS have very low values (0.5 db and less) due to better power supplies.

If you look to SS amps for power doubling as load impedance is halved, then you run the risk of being baited by the sales brochure. Very few SS amps can double down to 4 ohms, much less to 2 ohms. While Ohm's law says this is inevitable, Ohms law also states that the voltage decreases with an increase in power (current). As the load is halved, the PS voltage drops and lessens its ability to keep up the current flow. The PS voltage and current regulators have to be of top quality and the transformer has to have plenty of reserve in order to double down. That's why a single $20,000 100 watt Class A monoblock will have a power supply transformer thats more than twice the size of a $3,999 250 Wpc and more elaborate voltage and current regulation stages. That's where all the money goes.

Tubes watts are reputed to be louder than solid state watts. Of course this is not technicaly true. Tubes tend to overolad more gracefully than transistors. Jim Thiel told me that the recommended power given for his speakers were given with quality solid state amps, which could double down, in mind. He further recommended doubling those recommendations when using tubes, and to use the 4 Ohm taps on tube amps. Make sure the amps are up to the job at hand.