Watts! How many do we need?

The Sanders white paper is excellent. The two big takeaways are 1. that transient power demand is far higher than we think or that anything short of an oscilloscope can measure and, 2. the recovery time of the power supply in responding to transient power demands is critical.

"is an unltralinear watt identical to a triode watt? That’s a serious question, I am not intending to be sarcastic."

Basically, yes. But ultralinear operation has plusses and minuses. and a lot of those depend on the quality of the output transformer, the percentage of the screen taps relative to the plate taps, etc. You can get essentialy twice the power of triode operation (or more) but you also introduce stability and distortion factors that must be addressed. In a typical feedback amplifier, switching from triode to ultralinear operation requires adjustments in the feedback components to optimize the amp’s performance and stability. So a big question when buying a switchable amp is, does switching from one mode to another involve correctly adjusting the feedback components to allow for optimal performance? An amp oprimized for triode operation can encounter some serious issues when switched to UL mode, and vice versa. If no such arrangements are made, then one mode or the other is going to suffer. Often times, people with switchable amps will report that they tried the triode switch but didn’t like it because the sound quality was reduced. Or, they’ll report that triode mode was more "open" but the bass control was worse, etc. Usually these negative impressions are the result of the amp not being properly designed to optimize each mode of operation.

@bigtwin thanks for the Sanders white paper! An excellent read.

The Sanders paper is very interesting.  But one should remember a couple of things:

1) He's talking about ESL speakers in the main;

2) I think he exaggerates the frequency and extent of clipping in an appropriately matched system.

I would venture to suggest, at the risk of possible ridicule, that an audiophile in 1950 with a pair of Klipsch Cornwalls and a 15 wpc Wliiamson amp would rarely have encountered clipping and was probably enjoying a better musical experience than a lot of the power-eating systems available today.  In modern terms, I'll also stick my neck out and suggest that an audiophile with a pair of Vandersteen 1Cs and a well-restored Eico HF-87 will find a good deal of musical contentment with that arrangement, with far fewer headaches and travails than an amateur attempting to joust with walls of drivers and 600 wpc. ;-)

As a counter-argument to Sanders, I enjoyed this interview with amp designer Justin Weber, who essentially maintains that most audiophiles need *less* power than they think.  He also offers a very amusing and (IMO) very pertinent discussion about single-ended amplifiers:

@dogearedaudio   You are correct that Sanders is speaking about ESL for the  most part.  I listened to your attached file.  Very interesting.  I would suggest you could start at the 25 min mark as he doesn't really get into the meat of the subject before that.  Incredibly knowledgeable guy.  Kind of funny how many of the amps his own company produces are in the 50 - 100 watt range when 5 watts is sufficient for 95% of speakers and 99% of listening rooms (I think I got that right).  Anyway, a good listen for sure.  I liked his comment that we should all start by choosing our speakers first and then work backwards to the right amp.  Maybe that's why I liked the Sanders paper as I am running very large panel speakers.  Cheers.