Nice to have a special forum for a amplifierbrand. It will create a solid base of followers.
First of all I´m not a technician or audiodesigner. Just a customer of highend audiogear for the last 20 years.
Had the privilige to own several poweramplifier designs from Colangelo (ML-3), Agostino (KSA-100, KMA-200´s), Jeff Rowland (model 7 Series II, IV and model 8T) and Nelson Pass (S/300 and S/1000´s).
In the eighties Class A was the buzzword in highend and hifi world. John Curl designed for Levinson the ML-2 a 25 watt amp which consumed 400 watts at all times. Saw a lot of ML2´s with there heatsinks in time turned purple or even gold because of the heat. Krell was king in that area though. They specialized in copiing the designs of Levinson but make it even more outrageous with a designs like the KRS200 and six piece KRS-1. The more "modest" designs like the KMA-200´s drew a constant 1150 Watts from the outlet to retain the magical 200 watt Class A. It needed two noisy fans to cool it down. Threshold started with a original concept to tackle the constant draw of current with the dynamically biased 800A which at idling only consumed about 200 watts. In 1980 came the Stasis 1 (still the most sought after amplifier from Pass, also for it´s gorgeous looks, never superseded again in my opinion, probably thanks to Rene Besnee) with a completely new operating concept. From the accompanying brochure at that time: "Threshold Stasis amplifiers move beyond "class" designations through achievement of a completely new operating concept." In the accompanying tecnical paper (extremely readable though) a few years later with the introduction of the S/150 - 1000 series Nelson Pass stated that "While Class A operation was capable of reducing this effect (current variations in the gain devices) by swamping it with a large idle current, a method of reducing the current fluctuations would tackle the problem more directly. If one could envision a tandem arrangement of gain devices where current fluctuations were surpressed instead of voltage fluctuations as in cascode operation, this effect would be achived. Out of this concept came the STASIS amplifier.
So obviously there was no need anymore for that thermally stressing, power consuming ecologically unfriendly and in the summer to hot Class A biasing. Problem solved case closed! But then came the SA series after that the Aleph and now the XA series with a behemoth XA-200 of 80 kilograms idling just under the Krell and not even behaving as a voltage source because 200 Watts is the maximum you can get out of it according to the designer. The meter won´t move either than I suppose it just shows you the constant currentdraw from your pocket.
Krell (after abandoning the forced cooling and ridiculous large protruding sharp coolingfins (KSA-200 for example) and Levinson (always the more refined anyway of the two) got sensible and are now deploying plateaubiasing. Jeff Rowland has taken the real bold move to dispense with heat alltogether with his Icepower designs wich is the way of the future. He should only remove the heatsinks from his 300 series because there´s no need for it anymore just like the meter on the XA series.
So why is perspective with the other manufacturers of highend audio/amplifications has Nelson Pass revert back to energy wasting solutions from the past. Why is he back to square one in that parameter?
PS Found a series of photographs from the seventies of Threshold in www.passlabs.com/threshold One portrayed a Mark who later became president of MLAS. Is this Mark Levinson or Mark Glazier or just a stupid question.
First of all I´m not a technician or audiodesigner. Just a customer of highend audiogear for the last 20 years.
Had the privilige to own several poweramplifier designs from Colangelo (ML-3), Agostino (KSA-100, KMA-200´s), Jeff Rowland (model 7 Series II, IV and model 8T) and Nelson Pass (S/300 and S/1000´s).
In the eighties Class A was the buzzword in highend and hifi world. John Curl designed for Levinson the ML-2 a 25 watt amp which consumed 400 watts at all times. Saw a lot of ML2´s with there heatsinks in time turned purple or even gold because of the heat. Krell was king in that area though. They specialized in copiing the designs of Levinson but make it even more outrageous with a designs like the KRS200 and six piece KRS-1. The more "modest" designs like the KMA-200´s drew a constant 1150 Watts from the outlet to retain the magical 200 watt Class A. It needed two noisy fans to cool it down. Threshold started with a original concept to tackle the constant draw of current with the dynamically biased 800A which at idling only consumed about 200 watts. In 1980 came the Stasis 1 (still the most sought after amplifier from Pass, also for it´s gorgeous looks, never superseded again in my opinion, probably thanks to Rene Besnee) with a completely new operating concept. From the accompanying brochure at that time: "Threshold Stasis amplifiers move beyond "class" designations through achievement of a completely new operating concept." In the accompanying tecnical paper (extremely readable though) a few years later with the introduction of the S/150 - 1000 series Nelson Pass stated that "While Class A operation was capable of reducing this effect (current variations in the gain devices) by swamping it with a large idle current, a method of reducing the current fluctuations would tackle the problem more directly. If one could envision a tandem arrangement of gain devices where current fluctuations were surpressed instead of voltage fluctuations as in cascode operation, this effect would be achived. Out of this concept came the STASIS amplifier.
So obviously there was no need anymore for that thermally stressing, power consuming ecologically unfriendly and in the summer to hot Class A biasing. Problem solved case closed! But then came the SA series after that the Aleph and now the XA series with a behemoth XA-200 of 80 kilograms idling just under the Krell and not even behaving as a voltage source because 200 Watts is the maximum you can get out of it according to the designer. The meter won´t move either than I suppose it just shows you the constant currentdraw from your pocket.
Krell (after abandoning the forced cooling and ridiculous large protruding sharp coolingfins (KSA-200 for example) and Levinson (always the more refined anyway of the two) got sensible and are now deploying plateaubiasing. Jeff Rowland has taken the real bold move to dispense with heat alltogether with his Icepower designs wich is the way of the future. He should only remove the heatsinks from his 300 series because there´s no need for it anymore just like the meter on the XA series.
So why is perspective with the other manufacturers of highend audio/amplifications has Nelson Pass revert back to energy wasting solutions from the past. Why is he back to square one in that parameter?
PS Found a series of photographs from the seventies of Threshold in www.passlabs.com/threshold One portrayed a Mark who later became president of MLAS. Is this Mark Levinson or Mark Glazier or just a stupid question.
What's your motivation here? It sounds as if you're looking to bash a skilled designer for his design decisions. The advantages/disadvantages of Class A have been discussed to death in various forums, perhaps a few searches are in order before you call energy efficiency progress with no consideration of any other issues.
It does seem wastefull and excellent results can be had with other approches. However, by opperation no class is as pure as class A. The signal is never cut in half like in a AB or B amplifier nor is it ever hacked up then re-assembled like in a class D. As I said you can make an excellent AB,B,D,G ect. Amp, But for some people absolute pure, un-defiled audio is all that matters.
badman said:
What's your motivation here? It sounds as if you're looking to bash a skilled designer for his design decisions.
Certainly not! Have fond memories of the Threshold S/300 and S/1000 mono's in my system one of the most musical products I encountered. Love the NFB designs from Nelson Pass and Jeff Rowland. I'm seriously interested why the designer which skills I cannot and will not dispute has chosen for designs that waste so much power. That is a valid and legitimite question I backed up with the context I provided. Jeff Rowland stated it very elegant in one of his discussions he published named "A technical discussion With Jeff Rowland" subtitle: The Myth of "Class A" Operation"
last paragraph: "Most modern power amplifiers are quite inefficient and forwardthinking audio designers must become more ecological responsible by designing equipment which consumes less yet giver more." That's an opinion too made in the beginning of the nineties. Nelson Pass himself mentioned in his literature Stasis as the solution of all Class wars. He spoke over achieving linearity (his central topic in all of his discussions en designs) by swamping the circuit with biascurrent and propagated his Stasis solution as a less cruder and efficient way. I think it is in no way offensive to question/ask why a designer chooses to develop designs which waste so much power while he claimed in the eighties the end of the Class wars with his Stasis concept. You as a citizen of a country that in his First Amendment guarentees the freedom of speech shouldn't curtail me by saying I'm bashing a designer. Let's have a open discussion, I'm curious aren't you? Or is he a God...
The pic is Mark L, NP posted it when we had a talk overhere on Mr Levinson.
Small world, isn't it.
I've heard Mr Rowland's new age power amps.
Great design, but look and sound like refrigerators imo.
The pool in the backyard wastes a whole lot more, i kinda fancied nukes in a weird way too though.
Small world, isn't it.
I've heard Mr Rowland's new age power amps.
Great design, but look and sound like refrigerators imo.
The pool in the backyard wastes a whole lot more, i kinda fancied nukes in a weird way too though.
You will want to read this old post from Nelson on the subject:
http://www.diyaudio.com/forums/showthread.php?postid=558173#post558173
While it is true that the best power is the not-consumed one in terms of efficiency, I replaced a bunch of old light bulbs in the house with low-power ones. It turns out that I can enjoy many more hours of ClassA sound with an equal yearly electricity bill.
/Hugo
http://www.diyaudio.com/forums/showthread.php?postid=558173#post558173
While it is true that the best power is the not-consumed one in terms of efficiency, I replaced a bunch of old light bulbs in the house with low-power ones. It turns out that I can enjoy many more hours of ClassA sound with an equal yearly electricity bill.
/Hugo
jacco vermeulen said:
Thanks for the info on that picture.
Do you favour any particurly nuclear design? Fission or fusion Thermo-nuclear?
It's not the waste of energy only I pointed out. It cost you money the design is thermally stressed and the parts like the big toroids, heatsinks and so forth are costly items making the amp expensive.
The model 201 & 501 do look anything but not as a refrigerator. Though my refrigerator weighs less then a X-1000.5 or XA200.
How does a fridge sound anyway (don't say cold
BrianEno said:
Two quick comments before I run off to feed the boys...
1) You'll need to do a little homework before you say that the XA isn't a voltage source, simply because it tops out at 200W. It is a voltage source. That it doesn't increase wattage into low impedances is due to limitations on the bias current. The bias can easily be increased in that topology (something that would be anathema to you, apparently) and that would allow for full power into any arbitrarily low impedance that you might desire. The problem is that the amplifier would run hotter, require more power supply and heatsinking...and cost more. As a practical matter, designers have to stop somewhere.
2) You're spending far too much time reading, and vesting far too much emotion in sales literature. In case you haven't noticed, every new model from every manufacturer is lauded as a technological breakthrough of immense proportions. In direct consequence, they always claim to have rendered obsolete any and all pre-existing designs by any manufacturer...including themselves. Don't read too much into such claims, except for cynical entertainment value.
In passing: Your statement that class A subjects output devices to undue heat stress is poorly thought out. While it's obviously true that class A circuits run hot, each power cycle represents one heat cycle for the output devices; they get hot, stay hot, then cool down when the amplifier is turned off. Less aggressively biased amplifiers turn on, then get hotter/cooler/hotter/cooler/hotter/cooler...according to the demands of the music. This leads to many heat cycles every time the amplifier is turned on. Incidentally, this is one of many reasons that class A amplifiers are superior--the operating conditions for the devices are more consistent and distortion is inherently lower.
No one contests that class A amplifiers are more power hungry. That's simply the nature of the beast. Just how big a problem this is in terms of the environment is a matter of perspective.
Grey
Re: Re: Why Class A? Wasting power is something of the past
Thought that the perfect voltagesource has to double it's currentrating when the impedence halved to keep his voltage up like in Ohm's law. Now it turns out I'm wrong about that.
So what your saying that it could do that but the designer choose to do otherwise to keep the cost in balance. That must be a joke, you can't lift the XA200 by yourself and it costs a small fortune anyway with the restraints you mention. In fact you agree with me because as you say yourself: more bias requires an amplifier that would run hotter, require more power supply and heatsinking...and cost more
Apart from washingdetergent blahblah in the sales literature of even Nelson Pass products I take his technical exercitions in his technical papers somewhat more seriously then the brochures.
I have a Levinson ML-3 amplifier that is moderately biased for Class A and probably 90% of the listening is in that region and that will be the case for most of the Class AB designs. My other ML-3 operated for almost 30 years without problems.
I'm also not only taking in account conductors but also about electrolytics (saw some Sprague curves for them with diminishing life-expectancy by rising ambient temperatures) and soldering joints that crystalize.
Nice though to have a serious reaction on my questions.
Thanks
GRollins said:
Thought that the perfect voltagesource has to double it's currentrating when the impedence halved to keep his voltage up like in Ohm's law. Now it turns out I'm wrong about that.
So what your saying that it could do that but the designer choose to do otherwise to keep the cost in balance. That must be a joke, you can't lift the XA200 by yourself and it costs a small fortune anyway with the restraints you mention. In fact you agree with me because as you say yourself: more bias requires an amplifier that would run hotter, require more power supply and heatsinking...and cost more
Maybe that's not only truth for the sales literature but also for the products themselves. Class A has a magical ringing and when there's a market for it you tap in on that opportunity.
Apart from washingdetergent blahblah in the sales literature of even Nelson Pass products I take his technical exercitions in his technical papers somewhat more seriously then the brochures.
I have a Levinson ML-3 amplifier that is moderately biased for Class A and probably 90% of the listening is in that region and that will be the case for most of the Class AB designs. My other ML-3 operated for almost 30 years without problems.
I'm also not only taking in account conductors but also about electrolytics (saw some Sprague curves for them with diminishing life-expectancy by rising ambient temperatures) and soldering joints that crystalize.
Nice though to have a serious reaction on my questions.
Thanks
Re: Re: Re: Why Class A? Wasting power is something of the past
You are right about perfect voltage sources. But they are theoretical constructs that don't exist in reality. No amp is a perfect voltage source, whether it is class A, class B, class D or whatever. Neither is you mains outlet in the wall a perfect voltage sorce. Neither is a nuclear power plant. Anything in reality must have some limitations. However, within the limitations, we may consider amplifiers as approximating perfect voltage sources. But we must draw a limit somewhere. What about pluggin in a U-shaped copper bar instead of the speaker cable? Would you require the amp to keep up the voltage, just as a perfect voltage source would
BrianEno said:
You are right about perfect voltage sources. But they are theoretical constructs that don't exist in reality. No amp is a perfect voltage source, whether it is class A, class B, class D or whatever. Neither is you mains outlet in the wall a perfect voltage sorce. Neither is a nuclear power plant. Anything in reality must have some limitations. However, within the limitations, we may consider amplifiers as approximating perfect voltage sources. But we must draw a limit somewhere. What about pluggin in a U-shaped copper bar instead of the speaker cable? Would you require the amp to keep up the voltage, just as a perfect voltage source would
BrianEno,
If your intent is to rail again common practice in the audio industry, please be aware that there have been numerous threads over the years that took one or another (or all) manufacturers to task for advertising excess. We surely don't need another; it's all been said, ad infinitum, ad nauseum. Advertising is what it is. If you don't like it, don't read it. If you choose to read it, take it for what it is--mildly entertaining fiction, nothing more. Viewed objectively, it's no worse than the advertising for cars, cameras, or vacation hot spots.
If your intent is to ask technical questions as to why class A continues to be the class of choice, even after all these years of 'death-of-class A' pronouncements, you would do well to moderate your tone. At present, you sound more like you're spewing than asking serious questions. Bear in mind that the answers to may not suit you. Physics is implacable. Certain things are not open to negotiation. Mother Nature will allow certain work-arounds, some of the time, but don't think for an instant that there's an operating class that sounds as good as class A but uses only enough bias to power a flashlight.
Regardless of what the sales literature says.
Remember the "Have you searched?" button that you tagged in the process of starting this thread?
It's clear you didn't.
Grey
If your intent is to rail again common practice in the audio industry, please be aware that there have been numerous threads over the years that took one or another (or all) manufacturers to task for advertising excess. We surely don't need another; it's all been said, ad infinitum, ad nauseum. Advertising is what it is. If you don't like it, don't read it. If you choose to read it, take it for what it is--mildly entertaining fiction, nothing more. Viewed objectively, it's no worse than the advertising for cars, cameras, or vacation hot spots.
If your intent is to ask technical questions as to why class A continues to be the class of choice, even after all these years of 'death-of-class A' pronouncements, you would do well to moderate your tone. At present, you sound more like you're spewing than asking serious questions. Bear in mind that the answers to may not suit you. Physics is implacable. Certain things are not open to negotiation. Mother Nature will allow certain work-arounds, some of the time, but don't think for an instant that there's an operating class that sounds as good as class A but uses only enough bias to power a flashlight.
Regardless of what the sales literature says.
Remember the "Have you searched?" button that you tagged in the process of starting this thread?
It's clear you didn't.
Grey
BrianEno said:
I have a Krell-50 copy that shells out 700 Joules every second a few hours a day and it pleases me a lot more than the micro-wave.
The Mrs has been bugging me for a week to repair the Siemens wash-dryer, i told her we need energy awareness.
My kind of nuke, the best looking whale on the block : Astute
It's a legitimate question, nevertheless. Wasting power is
indeed something of the past.
Of course that depends on your definition of waste, and as I
pointed out before, the consumption of power is to be weighed
against the value it gives.
When I need to go somewhere, I give little thought to the
many kilowatt hours I have to use to accomplish it. When it's
particularly hot or cold, I will again spend kilowatt hours to be
comfortable. No Class A amplifier I ever built competes with
that consumption.
If you care enough about the sonic difference, then the energy
expenditure of the equivalent of a big plasma screen is worth it.
Clearly there is a small market segment for audio amplifiers
which consume high power, and that is why they exist. but there
are so few high end audiophiles running big Class A amplifiers
that it is not much of a target for those concerned about the
ecology.
If you are concerned about the environment and still want Class
A, the best thing to do is get some efficient loudspeakers and
buy or build little Class A amplifiers. In fact I recommend that
approach anyway, and between the Zens and First Watt, I
have made it easier for you....
indeed something of the past.
Of course that depends on your definition of waste, and as I
pointed out before, the consumption of power is to be weighed
against the value it gives.
When I need to go somewhere, I give little thought to the
many kilowatt hours I have to use to accomplish it. When it's
particularly hot or cold, I will again spend kilowatt hours to be
comfortable. No Class A amplifier I ever built competes with
that consumption.
If you care enough about the sonic difference, then the energy
expenditure of the equivalent of a big plasma screen is worth it.
Clearly there is a small market segment for audio amplifiers
which consume high power, and that is why they exist. but there
are so few high end audiophiles running big Class A amplifiers
that it is not much of a target for those concerned about the
ecology.
If you are concerned about the environment and still want Class
A, the best thing to do is get some efficient loudspeakers and
buy or build little Class A amplifiers. In fact I recommend that
approach anyway, and between the Zens and First Watt, I
have made it easier for you....
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