Power amplifiers with selector Class of operation?

My MSB M 204 mono blocks have also  the bias switch. Never used :)

VTL?

I have a late 70’s Yamaha B-4 that allows switching between ‘A’ and ‘A/B’. The only discernible difference I can sense is about 50 extra degree of heat. Great sounding amp though. 

cosmicjazz

Power amplifiers with selector Class of operation?

You want some like this, pity it isn’t made any more. 3w 10w 30w 100w of Class-A bias
https://ibb.co/0jZyD4Q

Next best is the Gryphon Antileon Evo. low, med, high Class-A bias
https://ibb.co/3CksBT7

And yes the Parasound John Curl designed Halo JC1 monoblock are great 10w or 25w switchable

Cheers George

Emotiva mono blocks have this feature. 

roberjerman, whether you think so, or not, speaker switching, brings the speaker output wiring, to the front, and then, back, to the rear of the amplifier, and, this, limits current, affects damping, and can only add / pick up noise. In your very large museum of power amplifiers, name me one American made power amplifier, that offers speaker switching. Bel, GAS, or whatever. When Adcom decided to eliminate the speaker switching, from the GFA 535, to the series II, this was an enormous upgrade ( other things, positive, changed, as well ). I can only imagine a Krell, Threshold or Levinson power amp ( of which I have owned many ) having speaker switching. Just use a 2nd amp, for a 2nd pair of speakers, or, change the speaker cables, manually, to the other pair. I find many statements of yours, ridiculous. But hey, we all have our opinions....Enjoy ! MrD.

Have made our Olympia Series of amplifiers with a Low Bias / High Bias switch for years.  https://pbnaudio.com/eb-sa-amplifiers/

Good Listening

Peter

Speaker switching is not harmful to an amplifier and is a nice feature to have when using two pairs of speakers.

This is typically a feature that allows amplifiers which are designed for a high bias current (i.e., mostly Class A amplifiers) to be run at a lower bias, as an energy saving feature.  The low bias setting typically decreases the power consumption and heat output, with the penalty being a decreased output in Class A (before switching to Class AB to provide the rated total power output), and some associated level of sonic degradation (i.e., increased distortion).  In addition to the amplifiers mentioned, some (but not all) Clayton Class A amplifiers include high/low bias switches.  

most amplifiers that have had a switch in the bias eventually go full nuclear and fail.

Probably the worst place in an audio circuit to put a switch.

It might take 10 years or more for it to happen and usually does take 10+ years....but consider it a done deal.

Tick tick tick......

You can’t afford to have those contacts in those particular switches to ever suffer any lack of contact, but..eventually they do.

It’s like all switches. They get dirty, and have contact issues, eventually. No exceptions that I’ve ever found. So, logically...

I'm not saying it's a deal breaker, as things should be good for quite a while.... 

Most plinius power amplifiers have a toggle that lets you select class a.

mijostyn beat me to it.  I found the lower bias setting on the JC-1s good for background listening and high bias (25 watts) better for critical listening.  A toggle switch on the back of each chassis so very convenient.

The Parasound JC-1 switches between 10 watts class A and 25 watts class A