Apart from your remark about the consensus in Europe about energy waste, I gather from your answer that every amplifier, seen from a sonically perspective, benefits from the implementation of an higher quiescent current. In the article ‘Leaving Class A’ Nelson Pass clearly indicates that (harmonic) distortion is inversely proportional to the bias current and the characteristic of the distortion gets better also. Moreover there’s a reduction of intermodulation distortion, a lower, more consistent output impedance. and the heavy hardware required to support Class A operation will show better thermal stability and will deliver better performance into difficult loads.
So in general not leaving Class A (especially in a complementary design) is a good thing as described in that article and every amplifier, not only the X and XA Series of PassLabs, benefits from a high level of biascurrent in their designs. Am I right?
I know the drawbacks of course: inefficiency and expensive hardware.
It’s a pity that I’ve no biasmeters on my Krell KRS-100’s but the AC energy meter in front of those two amps reads after approx. an hour 1250 Watts continuously and stays there even when I play at “earbleeding levels” on my very inefficient Infinity speakers (80dB/1W/1m).
Another thing:
I’m just curious which people you meant by:
“This counts less for some world citizens who can explain you perfectly that they have the "right to pollute".”
So in general not leaving Class A (especially in a complementary design) is a good thing as described in that article and every amplifier, not only the X and XA Series of PassLabs, benefits from a high level of biascurrent in their designs. Am I right?
I know the drawbacks of course: inefficiency and expensive hardware.
It’s a pity that I’ve no biasmeters on my Krell KRS-100’s but the AC energy meter in front of those two amps reads after approx. an hour 1250 Watts continuously and stays there even when I play at “earbleeding levels” on my very inefficient Infinity speakers (80dB/1W/1m).
Another thing:
I’m just curious which people you meant by:
“This counts less for some world citizens who can explain you perfectly that they have the "right to pollute".”
They benefit from a high(er) bias current. The crux being "er", not necessarily the absolute "high" an sich. That is what I distillate out of the articles, it is not my opinion.
According to some it is not necessary to burn 1250 Watts continuously when playing at a few Watts per channel (depending on speaker efficiency 1W is often already earbleeding) into the loads. It could also be done with the amplifier in question being in Class A till for instance 5W per channel. That will use the components in a good way while still maintaining moderate power consumption, reduce excessive heat and IMO more important: reduce wear out of parts. It is a choice. As often commercial interests and the tendency to dogmatic thinking create things like "only true class A is good", "ESS Sabre DACs have metallic highs" and such nonsense. Result is what counts and how it is done is of less importance. I have tricked a few that thought they were listening to a class A device (power LED on but not connected) while a Class D amplifier was playing.....I am tricked myself numerous times. Since then I force myself to not think in audio dogmas and I ended unexpectedly up with an FDA.
*Not "every" amplifier, I think it counts less for Class D. Maybe it is better to reduce to class A and AB.
If your device is true class A you will not see a difference in power draw either when volume is at 0 or when it is maximum. That is more or less the result of class A 😀
According to some it is not necessary to burn 1250 Watts continuously when playing at a few Watts per channel (depending on speaker efficiency 1W is often already earbleeding) into the loads. It could also be done with the amplifier in question being in Class A till for instance 5W per channel. That will use the components in a good way while still maintaining moderate power consumption, reduce excessive heat and IMO more important: reduce wear out of parts. It is a choice. As often commercial interests and the tendency to dogmatic thinking create things like "only true class A is good", "ESS Sabre DACs have metallic highs" and such nonsense. Result is what counts and how it is done is of less importance. I have tricked a few that thought they were listening to a class A device (power LED on but not connected) while a Class D amplifier was playing.....I am tricked myself numerous times. Since then I force myself to not think in audio dogmas and I ended unexpectedly up with an FDA.
*Not "every" amplifier, I think it counts less for Class D. Maybe it is better to reduce to class A and AB.
If your device is true class A you will not see a difference in power draw either when volume is at 0 or when it is maximum. That is more or less the result of class A 😀
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The graphs are clear, the more bias the better end about the the crux being "er" the article clearly indicates:
"The whole point of going to this trouble is to build an amplifier which sounds as good as possible. We find that this is achieved by building a simple amplifier which is intrinsically distortion-free. Getting that depends on a high bias.
If you have a efficient horn loudspeaker a single ended Class A triode amplifier will be sufficient of course.
According to Nelson Pass it's not only beneficiary in reducing distortion but:
" As a corollary benefit, the heavy hardware required to support Class A operation will show better thermal stability and will deliver better performance into difficult loads."
It says this:
As a practical matter, this means that our X (Class AB) amplifiers are biased to dissipate roughly half of their rated output power. The XA (Class A) amplifiers are biased to dissipate roughly three times their rated output power.
The whole point of going to this trouble is to build an amplifier which sounds as good as possible. We find that this is achieved by building a simple amplifier which is intrinsically distortion-free. Getting that depends on a high bias.
So that is relative as their AB devices consume half of the rated output power (this would be called very high biased or possibly even class A at other brands) and 3 x rated output power with their class A devices. "High" both in AB and A while we both know that high in A is higher than in AB. You see?
It would be more clear if was mentioned that class A has "highest" bias current 🙂
As a practical matter, this means that our X (Class AB) amplifiers are biased to dissipate roughly half of their rated output power. The XA (Class A) amplifiers are biased to dissipate roughly three times their rated output power.
The whole point of going to this trouble is to build an amplifier which sounds as good as possible. We find that this is achieved by building a simple amplifier which is intrinsically distortion-free. Getting that depends on a high bias.
So that is relative as their AB devices consume half of the rated output power (this would be called very high biased or possibly even class A at other brands) and 3 x rated output power with their class A devices. "High" both in AB and A while we both know that high in A is higher than in AB. You see?
It would be more clear if was mentioned that class A has "highest" bias current 🙂
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Why restrict yourself to having only one? I own two cars, one is simple gas saving 4 banger that I use for daily commuting. Great on gas and easy to fix. I also have another car that’s makes lots of horsepower, fun to drive, but crappy on gas so I don’t drive it everyday; it’s a weekend car. I’m a big believer in highly efficient speakers. If I’m doing critical listening with a tasty beverage, Class A all day but if its background music grab a Class A/B. One of the beauties of DIY, build what you want. Ill soon have enough amps to swap out daily like underwear.
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That's exactly what I do
I have a daily to use hifiset in my livingroom with a Classe Audio DR-6 pre an Threshold Stasis 3 amplifier and in my office I use also a Classe Audio DR-4 pre and Audire Forte amp for background listening.
So most of the times I listen to crappy Class AB amps 😉
I have a daily to use hifiset in my livingroom with a Classe Audio DR-6 pre an Threshold Stasis 3 amplifier and in my office I use also a Classe Audio DR-4 pre and Audire Forte amp for background listening.
So most of the times I listen to crappy Class AB amps 😉
Don't be fooled by that because in effect that means that the X-600 amplifier rated for 600 Watts is biased at 300 Watts (600/2) and the same chassis and hardware the XA-160 is biased at 480 Watts (160*3).
That doesn't make that big a difference.
Friend of mine had a pair of X-600's operating on Acoustat 2 + 2 fullrange electrostatics with a very low efficiency (lower as 80dB's) and his meters never moved away from their static position.
You shouldn't need me to explain "relative","absolute" and "picking random" isn't it? The given text was as relative as can be. Now religion, dogmas, predefined "truth", opinionated reasoning etc. can make matters quite diffuse.....
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Audire Forte
Do you mean Audio Forte? What model?
Even I'm sure that you know who is behind or was behind Audio Forte, it's also Mr. Nelson Pass, and these are far away from being crappy. BTW most of Audio Forte are CLASS A.
I owe one by myself. Audio Forte A100 - CLASS A
@jean-paul
Did you ever hear the saying "hidden power"
That is the reason to burn away 650Watts Idle for 1 Watt listening power.
IF you listen to Music, there is as well Rock Music as also Classical music where the Loudness of the sound is from almost no sound to extreme loud.
There it is where Class A kicks in, literally spoken.
I'm sure you also know that 3db louder takes double of Power.. But sometimes there are Spikes in Music which increasing 10 and more DB for a short time, and this means 20Times the power..
Again, Class a is like a BIG PIPE where the full Power is just hidden by the Volume control. As soon, you turn it up, then there is no need to get the Current into the Transistor, Full Current already available, therefor, is the 650Watts..*I know that's far too much* and I'm also using only CLASS A.
I'm working since a long time on a class a, and trying to let that CLASS A getting smart. With reading the Documents of Rod Elliot, and also building them as well as reading all DOCS, of Nelson Pass, I'm close to finish line.
Getting a Class A where the AMP knows what comes next and so will adjust the Bias by itself, for the time being. If sound goes quiet, and stays longer than 1 minute quiet the AMP will reduce BIAS Current. As soon signal is back then the AMP will increase BIAS to max.
I could make this with a DIGITAL Circuit, but I try to have this analogue. Digital in AMPS, is no good.. You never get that out again..
I'm talking about REAL CLASS A, mine at home between running on 35 / 48 Volts Vrail+ and Vrail - @ 4 - 6 Amps idle current. Go to page 2 to look at the pics.
So, the other day I've got my electricity bill, 2675 Swiss Francs, *2600 EURO* for 6 months.. Where regular Households the size of mine would pay only a tenth, for the same period. Quite a lot! But switching the AMP on and off is no Option, even I have a Controlled Wall outlet with remote control.
So, as I said, trying to create a STANDBY mode, but one where the AMP know by it self when to wake up. This will reduce "Wasted Power where no signal is used" by at least 80%.. not because I'm a greeny or likewise, but just because, it makes no sense, buying expensive heat, therefor I have a heater, which is a lot cheaper.
Now, I also do not want to MISS that Premier Excellent Sound of CLASS A when it's running. and therefor - Only Class A is good enough.
Thanks for Reading.
Regards
Chris Hess
Bern Switzerland
No I meant Audire the company of the late Julius N. Siksnius (participator of the Apollo project) not Forte the "B" line (no disqualifying intended just for clarification) from Threshold.
Catch 22 is that XA amps are weeeeeell underrated with declared power
so, situation looking more rosy, from efficiency stance
so, situation looking more rosy, from efficiency stance
Krell introduced this kind of scheme in 1993 with their plateau biasing line of amplifiers KAS, KAS-2, KSA-300s, 200s, 100s and 50s.
Nelson Pass first amplifier the Threshold 800A had also a dynamically biased topology I believe.
With power consumption being half of the rated output power things are already rosy on the efficiency front, regardless of output power. So if they deliver more output power in reality and consume let's say only one third of the real output power things are more efficient indeed. Still the AB devices are relatively high in bias current so at least some of the benefits of high bias also count for those specific AB devices. I mean, at the other side of the spectrum there are chipamp class AB amplifiers with just 40 mA bias current.
I think the thread title should have the question mark removed (and a typo corrected) as it seems opinion rebadged as a question.
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As is the case with my Krell KRS-100 which is rated for 100 Watts RMS @ 8 Ohms (hence its name KRS-100) but actually it delivers twice that power according to this rapport:
https://www.diyaudio.com/forums/attachment.php?attachmentid=936312&stc=1&d=1616858580
And the technician also states (translated from German)
"Very harmoniously falling harmonics, from today's point of view very advantageous in terms of sound."
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Yes I know.
I'm taking another Approach, then what Krell and Mr. Pass did
I will cut the power down, to almost nothing, but the AMP still has some sound in CLASS A Mode and about 2 watts, as signal increases Full BIAS will be applied. and then also the period of time can be adjusted by the owner or user or whoever uses the amp.. it also can be switched that this SMART PART is off.
I'm taking another Approach, then what Krell and Mr. Pass did
I will cut the power down, to almost nothing, but the AMP still has some sound in CLASS A Mode and about 2 watts, as signal increases Full BIAS will be applied. and then also the period of time can be adjusted by the owner or user or whoever uses the amp.. it also can be switched that this SMART PART is off.