Hybrid vs. Straight Tubes

I owned a Leben CS600. Very nice unit, but you should listen to it driving your speakers before you open your checkbook.

91 db speakers driven by a 10wpc amp would produce 100db peaks at 8wpc measured at a distance of 1 meter from the drivers (91db at 1wpc, 94db at 2wpc, 97db at 4wpc, 100db at 8wpc). To determine if this is sufficient, you need to measure the decibel level peaks at the loudest volume you might expect to reach during your most aggresive listening session.

Wattage still does relate to loudness, but you also get the same loudness with less power if you have more efficient speakers. The other issues is how an amp handles clipping (tubes do it well, SS not so good), and short dynamic output for handling transients - and you can't really tell that from wattage. Some 50 watt amps have tremendous dynamic power that is only needed for very short periods of time and can sound every bit as "loud" and a 200 watt amp that doesn't handle transient power delivery quite as well. I can tell you a Pass XA30.5 sounds like a lot more power than many other "30 watt" amps.

Have owned SS up until just a few days ago, when I had and took the opportunity to trade my Nuforce class D 160w mono's for a Cary Rocket 88R (30w triode/60 ultralinear). Despite the low power rating I notice no degradation in sound quality, even at fairly loud levels running in triode. I was afraid that my Usher 87db/8 ohm (dipping into 4 ohms) speakers wouldn't be a good match for tubes. The Cary is happily putting that notion to bed. Quite happy with the sound.

I'll add that I had 3 different tubed preamps in front of my SS amps over the time I owned them, none of the combinations have come close to the character of the tube amp/passive pre combo I'm running now. The magic IME lies in tubed amplification.

Mechans' comment re: "tube output stage is critical, period" is probably fair enough, overall. In the case of the RS6, it's even more applicable. Speakers which have a spike in impedence in the presence range (IIRC, the RS6 qualifies - as does the Merlin VSM, another speaker that "flatters" tube output stages) sound more dynamic and alive with the right tubed ouput stage. You might get a taste with tubed drivers and SS output, but you won't get the whole deal.

Good Luck.

Marty