Solid State vs. Tubes - What if Transistors came first?

@fleschler, Roger Modjeski also get’s 100 watts out of a pair of KT88’s in his Music Reference RM-200 Mk.2, with well less than 1% distortion (look at the listening impressions and bench test results in it’s review in Stereophile a few years back). He does so not by driving the tubes hard, but by creative engineering. I somewhere read his explanation of how he did it, but don’t recall where. Give him a call, he likes to talk and is a real swell fella.

Well, I believe that John Curl went into a very enlightening discussion on how easily the standards can be gamed, not that that's happening in this case, but specifications are a lot more pliable than most understand. Again, I don't know these manufacturers, but 50wpc rms into 8 ohms is 100wpc rms into 4 ohms, and 50wpc rms is 100wpc, to name a few ways to spin things that I am familiar with. New Sensor claims 2 x 33 watts max for their tubes, 2 x 30 being the norm, so 50wpc gives you a nice cushion but 60wpc is within spec. Perhaps you ought to be asking those manufacturers how they can get more out of a tube than the manufacturer of the tubes says is reasonably possible. OTOH, if you listen to Kevin Deal of Upscale Audio, within a particular tube line, acceptable specifications greatly vary, so presumably they could be buying only tubes that exceed specifications. I personally would consider that to be deceptive unless they insist that those outputs are only obtainable using tubes sold by them. Furthermore, the best of the best tubes fade, so be it 100wpc, or 50wpc, as tubes age, your output capability will drop!

I’m not sure how tubes are rated, and am by no means a tube amp expert, but if you attach the tubes in bridged mode, instead of push-pull you could get 2x the voltage, or 4x the power. So assuming this is done, it seems quite plausible to me that you could get 60 watts RMS out of a pair of 33 watt (peak) tubes.

The proof is in the listening however. The difference in dB between 60 and 40 watts is only 1.76 dB. Point being, things look a lot more different in wattage than they sound.

The wattages quoted, 30 something, is pertube, in a pushpull amp you'll double that.

Oh, so bridged mode allows a 50% increase without exceeding distortion performance standards.  I forgot about the RM-200 which I also liked and heard many years ago.  I doubt that Kevin Deal is selecting tubes which only exceed specs as many people reported excellent results with NOS and other brands of current tubes as well.  I just thought that pushing the tubes harder, if that's what 100+ watt per pair might due, would lessen their effective life.  I know several friends with Audio Research gear of the 1990s/2000s who decry the short lifespan of their output tubes.  

My output tubes are run conservatively (6-6BG6) to produce 125w.  So cool that the transformers are just barely warm to the touch after 3 hours of dynamic music listening.  They last about 3,000 hours (luckily they are NOS and cost only $7 a tube).