4-ohm setting with 8 ohm speakers

And to complicate matters a little bit with what will likely be a footnote to the discussion, it should be mentioned that output transformerless (OTL) amps actually increase their output power into higher impedance speakers. Atma-sphere amps are the most well-known OTL amps although there are also OTLs from Tenor, Transcendent (incl kits) and others.

This makes Speltz autoformers particularly helpful with these OTL amps, although as the Speltz site testimony makes clear the autoformers can improve sounds with other amps as well.

Rrog, An example in ss amps is the Harman Kardon amp(s) in the Citation series years ago when hk abandoned their decent quality American-made amps for the Japanese-made lower quality amps after they bought Levinson. Not that there's anything wrong with Japanese-made per say. I think their 4-8ohm taps were to compensate for a less muscular amp that could not handle a 4 ohm load except at the expense of sound quality. And I think this device in ss is sometimes used to compensate for an anemic amp. I'm always suspicious when I see this device in ss, but I realize it has its place. My predjudice also comes from my dislike of switches which degrade sound quality.
I apparently didn't articulate my initial point very well because I surely don't have anything against using the tap that sounds the best as long as it doesn't cause damage to the amp. That's kinda the whole point of the tap. I don't have a technical background as some of you know, but I do understand in general impedence matching of amp and speakers. There is an optimum load for every amp. That is the point of the taps and the point of autoformers, a device used to find that optimum load. Lynne

I don't know about impedance matching, but if you want a high damping factor the idea is to get speaker / amp impedance pretty much as far apart as possible.

4/8 ohm switch or taps on SS? Maybe to limit power into lower impedance loads to make up for an inadequate PS.

The 'best' load for an amp? Probably a resistor. Than it turns into degrees and how well an amp handles reactive loading.

Check out the link to the 'power cube'...not an amp, but a measuring system.
As always, good specs DO NOT guarantee good sound.

http://www.audiograph.se/Downloads/PowerCube_12p_brochure_complete.pdf

Magfan, looks interesting. Do you know any reviews in which it has been used?

Darn good question....and I have NO answer. You'd think if a manufacturer were proud of a top amp, they take the data and Brag.
Considering the cost of electronic test equipment, this would be a drop in the bucket. Stereophile even skips this test. A plain old resistor is good enough for them!

OTOH, Who the heck knows how to interpret this data except for some fringe tehno-geek types?

Than what would happen of some highly regarded amps crapped out in this test?
When testing a tube amp, should you change taps as you change load impedance?
What about tube amps not being happy with capacitive loads? (I think this is right, and it isn't inductive)