Ditching Class A Amps due to Heat - Sort of a Poll

@yyzsantabarbara     No I haven't.  I am not looking much for upgrades any more and I don't go out listening to new kit.  After nearly 60 years, I'm in the lucky position that I love my system the way it is.  I occasionally buy a phono cart, mainly top-end Ortofon.  I changed my pre-amps 4 years ago from old Audio Research to vdH The Grail and Audio Research Ref 6.  Otherwise it's all old stuff.

I read Krell Solo 575 Mono Power Amplifier 575 Watt Amplifier features 'iBias'.  This is said 'to deliver the rich musicality of Class A amplifiers, the uncompromised dynamics of classic Krell amplifiers, and the efficiency and low power consumption of Class G and H amplifiers.'  Sorry.  I don't believe you can get something for nothing.  In their publicity Krell extol the virtues of Class A and pretend they are still building it.  Neither do I trust Krell since the D'Agostinos were fired.  The way that was done suggests the new owners are bad guys not to be trusted.

In 2015 they cost $22,500/pair.  Not a lot, in the context.  Fremer's 2015 review was 'equivocal', although Atkinson found it measured 'impressively'.  For those that are concerned, the power supply isn't stiff; output doesn't double up down to 4 ohms, let alone 2.

The minimal amount of heat from a class A amp is equal to 4 x 100 watt light bulbs approx. no big deal and since I love the sound I see no reason to ditch the amp becauseof heat, unless one wants a new toy for the sake of a new toy.  

The cost of elctricity in my area is 12.5 c per kw hour.  Multiply by .4 kw and my amp costs 5c per hour to run.  I am more than happy to put another nickel in the slot every hour :) 

Maybe class A amps will become more popular when homes are mandated to have non fossil fuel or natural gas heating. 

Compared to a 36.2 kw electric furnace .4 kw ain't nuthin.  

@avanti1960 Wrote:

The minimal amount of heat from a class A amp is equal to 4 x 100 watt light bulbs approx. no big deal and since I love the sound I see no reason to ditch the amp becauseof heat, unless one wants a new toy for the sake of a new toy.

The cost of elctricity in my area is 12.5 c per kw hour. Multiply by .4 kw and my amp costs 5c per hour to run. I am more than happy to put another nickel in the slot every hour :)

I agree! 😎

Mike

in the sense that it does what it’s designed to do, prevent notch distortion (the basic reason we want Class A) while reducing power consumption.

@axo1989 

Just so you know, any class D amp that uses a choke-filtered output (which is nearly all of them) are incapable of notch or crossover distortion.

I read Krell Solo 575 Mono Power Amplifier 575 Watt Amplifier features 'iBias'.  This is said 'to deliver the rich musicality of Class A amplifiers, the uncompromised dynamics of classic Krell amplifiers, and the efficiency and low power consumption of Class G and H amplifiers.'  Sorry.  I don't believe you can get something for nothing.  In their publicity Krell extol the virtues of Class A and pretend they are still building it. 

@clearthinker

Krell has used a sliding class A bias system for years. The way it works is at lower signal levels the bias is also reduced. As the amplifier power increases, the bias linearly increases with it. In this way it can be biased in the A region all the time (in this case meaning both output transistor banks are active throughout the entire signal waveform) at any power level the amp makes. Because music tends to have lots of transients that are short duration, even though the amp might be quite powerful the net result is it will run cooler and draw less power, significantly so.

If you were to run it at full power long enough for it to heat up, you would find it making the same heat and drawing the same power as any class A amp capable of the same power.

My point here is that its not a 'get something for nothing' proposition as you suggest. Seems to me there was a patent issued on this technology back in the 1990s.

The heat generated from a class A tube amp is significant and can be annoying.  I have a Black Ice Audio Fusion and a Cary tube amp.  I can only run them in the cooler late autumn through the winter seasons.  The rest of the year I run bridged Schiit Aegirs and Outlaw Audio 2200 monoblocks.  For class A, the electrical cost is not the issue; it's the heat.  If the bias current is not spot on, the amps will overheat and shut down.  The Black Ice uses four 6550s and the Cary uses eight KT88s.  Yes the 6550s are the functional equivalent of oven coils although KT88s are slightly cooler.  This may be sacrilege, but if I had to do it all over again, I would go with class D.  My Ampeg SVT tube amp runs nowhere as hot as these stereo amps.