Class A vs AB vs D amplifiers

[Blenderguy]

Back on track for topic
How many people are aware of the Spirito phenomena? I had read about BJT destroying themselves through secondary breakdown, but now it appears that Mosefets are not completely bulletproof. So the chance that the output stage of a class D amp will fry is not out of the question.

https://www.analog.com/en/_/media/analog/en/landing-pages/technical-articles/mosfet-safe-operating-area-and-hot-swap-circuits/spirito-region.jpg?h=270&hash=90D68217DB3FA03FB7CCB891F65D216AC2655425&rev=14e97b2a2d0348848faa24fd68810630&sc_lang=en

Complete article here:

https://www.analog.com/en/resources/technical-articles/mosfet-safe-operating-area-and-hot-swap-circuits.html

 

[Blenderguy]

Did you actually take the test?

I did, I have a topping DAC and was able to detect some kind of change at around 0.2 to 0.3% I only did the 1kHz test because the distortion level on the phones was too high to determine any appreciable change at the lower tone. I assume we are a science based forum, so was just pointing out the technical defect.

 

[MAB]

I did, I have a topping DAC and was able to detect some kind of change at around 0.2 to 0.3% I only did the 1kHz test because the distortion level on the phones was too high to determine any appreciable change at the lower tone. I assume we are a science based forum, so was just pointing out the technical defect.

OK, so you didn't take the Klippel listening test. It is two music tracks, and two multi-tone tracks for reference.

 

[wwenze]

Back on track for topic
How many people are aware of the Spirito phenomena? I had read about BJT destroying themselves through secondary breakdown, but now it appears that Mosefets are not completely bulletproof. So the chance that the output stage of a class D amp will fry is not out of the question.

https://www.analog.com/en/_/media/analog/en/landing-pages/technical-articles/mosfet-safe-operating-area-and-hot-swap-circuits/spirito-region.jpg?h=270&hash=90D68217DB3FA03FB7CCB891F65D216AC2655425&rev=14e97b2a2d0348848faa24fd68810630&sc_lang=en

Complete article here:

https://www.analog.com/en/resources/technical-articles/mosfet-safe-operating-area-and-hot-swap-circuits.html

Class D output transistors are fully on, so that is not a problem.

 

[pma]

Simultaneous ON of top and bottom halves of MOSFET switch must be avoided, as it would destroy the parts immediately. So some “dead zone” must be implemented.

 

[MaxwellsEq]

Back on track for topic
How many people are aware of the Spirito phenomena? I had read about BJT destroying themselves through secondary breakdown, but now it appears that Mosefets are not completely bulletproof. So the chance that the output stage of a class D amp will fry is not out of the question.

https://www.analog.com/en/_/media/analog/en/landing-pages/technical-articles/mosfet-safe-operating-area-and-hot-swap-circuits/spirito-region.jpg?h=270&hash=90D68217DB3FA03FB7CCB891F65D216AC2655425&rev=14e97b2a2d0348848faa24fd68810630&sc_lang=en

Complete article here:

https://www.analog.com/en/resources/technical-articles/mosfet-safe-operating-area-and-hot-swap-circuits.html

But, but, but... everyone knows this stuff who has ever designed using BJTs and FETs. It was probably one of my first lectures of a 3 year EE degree course.

 

[DonH56]

Back on track for topic
How many people are aware of the Spirito phenomena? I had read about BJT destroying themselves through secondary breakdown, but now it appears that Mosefets are not completely bulletproof. So the chance that the output stage of a class D amp will fry is not out of the question.

https://www.analog.com/en/_/media/analog/en/landing-pages/technical-articles/mosfet-safe-operating-area-and-hot-swap-circuits/spirito-region.jpg?h=270&hash=90D68217DB3FA03FB7CCB891F65D216AC2655425&rev=14e97b2a2d0348848faa24fd68810630&sc_lang=en

Complete article here:

https://www.analog.com/en/resources/technical-articles/mosfet-safe-operating-area-and-hot-swap-circuits.html

Any class D amplifier from the very first design has included a (usually very simple) circuit to incorporate a small "dead zone" so that both output devices (of whatever type) are not on at the same time. Part of the improvements in performance have been minimizing and compensating for that dead zone.

Of course, normal output protection is also present, to prevent damage when the load short circuits, or thermal limits are exceeded, and so forth in addition to the usual SOA (safe operating area) design consideration that is part of any design.

 

[mhardy6647]

I've not measured recently - since retirement I don't have access to the kit so far.

I just want to go on record as saying that I note with pleasure the last two words of the sentence quoted above.

 

[pogo]

Any proof?

The bridged/un-bridged THD+N measurements (see diagrams!) probably give an indication: Link

 

[pma]

The bridged/un-bridged THD+N measurements (see diagrams!) probably give an indication: Link

Would you try this test (crossover distortion of -62dB with harmonics up to 20th)

Master Thread: Are measurements Everything or Nothing?

Here are the plots for the offending amplifier (shown in green on all graphs). The second amplifier used in the ABX test was the AHB2 (shown in red on all graphs). These tests plots were made in 2016. Thank you for the data provided, I appreciate it.

www.audiosciencereview.com

when arguing with such low level of THD+N audibility?

 

[pogo]

Whether it is these better measured values or others that were not recorded, who knows. In any case, I and others can hear this difference: Link

 

[voodooless]

Whether it is these better measured values or others that were not recorded, who knows. In any case, I and others can hear this difference: Link

Lots of people claim lots of things, like hearing differences when putting silly crystals on any IC in their equipment, and others hear it too. This is not a good argument, and you know it.

 

[SIY]

The bridged/un-bridged THD+N measurements (see diagrams!) probably give an indication: Link

OK, so the answer is, "No, I have no evidence whatsoever. Again."

It's a tiresome shtick.

 

[rank]

I have always had immense difficulty hearing the striking differences between amplifiers, whatever their types.

 

[Doodski]

I have always had immense difficulty hearing the striking differences between amplifiers, whatever their types.

I agree. I've heard so many amps on switchboxes that I think I can only estimate the amount. They all sounded pretty much the exact same.

 

[dlaloum]

I agree. I've heard so many amps on switchboxes that I think I can only estimate the amount. They all sounded pretty much the exact same.

You just need to pick a nicely discriminating 1ohm speaker....

Then lots of amps will sound different.... some of them may go up in smoke too... or shut down to self protect.

 

[Doodski]

You just need to pick a nicely discriminating 1ohm speaker....

Then lots of amps will sound different.... some of them may go up in smoke too... or shut down to self protect.

I know this and fully agree with you. For that I would be suggesting a beasty linear output amplifier. But for general amp tests 4 Ohms and 8 Ohms works fine.

 

[rank]

At 1 ohm I only know the old Apogees. The Full Range and even the Scintillas I think (the latter easier to drive). It's close to 0 ohm which seems problematic in theory but any real class A amp can hold them.

Like the Mark Levinson ML-2 or some Krells. For cheapos, the Hiraga in diy but I think he could no longer be repaired because of certain components having unfortunately disappeared without equivalence. The problem = the lack of power, old Apogees have low efficiency.

 

[goryu]

Purifi 9040. Stable to near short, 1200+ watts.

 

[Koeitje]

I have always had immense difficulty hearing the striking differences between amplifiers, whatever their types.

I have no problem with this with many amplifiers. The only problem I have with my methodology is that I just need to push one amp into clipping while the other isn't running out of power just yet. Sometimes I don't need to do that, but in those cases I don't feed them any signal because you sometimes hear the difference in noise floor quite easily. That is completely masked by the noise floor from almost any recording though.

At 1 ohm I only know the old Apogees. The Full Range and even the Scintillas I think (the latter easier to drive). It's close to 0 ohm which seems problematic in theory but any real class A amp can hold them.

Like the Mark Levinson ML-2 or some Krells. For cheapos, the Hiraga in diy but I think he could no longer be repaired because of certain components having unfortunately disappeared without equivalence. The problem = the lack of power, old Apogees have low efficiency.

I would call those speakers to badly designed. But its fun to talk about because of how silly those speakers really are.