Handling a complex load by power amplifiers

[sarumbear]

Not at all what I'm saying.
I'm pointing out that the review should be objective by showing test results and price. The product should not be higher regarded because it is cheap or expensive. That should be up to the reader to decide IR to the personal budget.

Do they not show test results and the price? Please show as an example.

 

[tmtomh]

I guess it boils down to the recommendation part of it all and the seemingly endless praises of small chinese amps with load dependency swiftly put in an extruded aluminium case without full disclosure of e.g. (Torsten) electrical compliance. -And that I think we could get an objectively better view of it all with proper complex load testing.
I really think Torsten has made some excellent points in his posts earlier on.

So small size, Chinese brand, load dependency, the type of metal used for cases, and how quickly the amps are allegedly placed into those cases are all equally significant problems?

That praise for these small Chinese amps “seems” endless to you, and that you “think” more complex loads would reveal new things, are not evidence-backed claims for changing how reviews are done here. @amirm has begun using more complex simulated loads, and they’ve produced exactly zero new or unexpected results.

It’s striking how someone who’s so upset about Amir giving recommendations based in part on allegedly non-objective factors is himself so dedicated to sticking to his own subjective impressions and opinions even when they are contradicted by the facts.

 

[sarumbear]

I guess it boils down to the recommendation part of it all and the seemingly endless praises of small chinese amps with load dependency swiftly put in an extruded aluminium case without full disclosure of e.g. (Torsten) electrical compliance. -And that I think we could get an objectively better view of it all with proper complex load testing.
I really think Torsten has made some excellent points in his posts earlier on.

Recommendations are @amirm ’s personal, hence subjective views. Tests are there to speak for themselves. If you don’t process the tests than maybe you consider to go to other forums where people just talk.

 

[Deleted member 48726]

Recommendations are @amitm’s personal, hence subjective views. Tests are there to speak for themselves. If you don’t process the tests than maybe you consider to go to other forums where people just talk.

Seems to me I'm exactly where I need to be then..

 

[IPunchCholla]

I guess it boils down to the recommendation part of it all and the seemingly endless praises of small chinese amps with load dependency swiftly put in an extruded aluminium case without full disclosure of e.g. (Torsten) electrical compliance. -And that I think we could get an objectively better view of it all with proper complex load testing.
I really think Torsten has made some excellent points in his posts earlier on.

I've blocked his posts, but the one that I did see was full of racist conspiracy theories. Which Chinese manufactured amps that Amir has recommended have non-full disclosure of electrical compliance? I've noticed in several reviews where he has called out no UL or CE compliance on products he is reviewing, but is that an issue with the A07?

 

[restorer-john]

One thing that has come up in this thread and in others on this site is that some people are accused to "hanging on" to outdated class AB amp technology and not fully embracing class D technology. In my case at least it is not really Class AB vs Class D but rather my attachment to the old ideal that an amplifier should be a "wire with gain". While class D has proven it can be very linear and powerful and efficient in the audio band it certainly is a step backwards on the "wire with gain" goal. I know all the reasons why all the added HF doesn't matter and can't be heard but it still "bugs me". The best "cure" for this is listening to class D amps which sound great but when ever I see graphs with all that extra HF it still gives me pause.

Well said.

Preamplifiers and power amplifiers became DC-daylight straight wires with gain in the 1980s. Linearity was nailed, well below the thresholds of audibility with no side effects, no out of band nastiness and little to no load related interactions of significance. So, "outdated" or "hanging on"? Hardly.

Class D has got really good, really quickly, but it has its own set of baggage it brings to the party. As I stated many times before, if I was starting out in HiFi, without the knowledge I have, I'd definitely consider a Class D high performance amplifier.

As for recommendations or lack thereof @amirm gives, he can't win, whatever he does. If he considers the price, the scales change. But when the price is astronomical or ridiculously cheap, that has to weigh in to the recommendation too. Fractions of a dB separate many devices and we all know how dubious rankings become in that situation. He's between a rock and a hard place and does his best.

 

[MaxBuck]

I'm open to the idea that my inability to distinguish between good amplifiers doesn't necessarily extend to others.

If only so many others say they can't distinguish either.

That said, the notion that interaction between good amplifiers and complex speaker loads can lead to audible differences doesn't strike me as outlandish.

 

[Deleted member 48726]

I've blocked his posts, but the one that I did see was full of racist conspiracy theories. Which Chinese manufactured amps that Amir has recommended have non-full disclosure of electrical compliance? I've noticed in several reviews where he has called out no UL or CE compliance on products he is reviewing, but is that an issue with the A07?

Racist?? That's harsh. Show me.

 

[tmtomh]

I'm open to the idea that my inability to distinguish between good amplifiers doesn't necessarily extend to others.

If only so many others say they can't distinguish either.

That said, the notion that interaction between good amplifiers and complex speaker loads can lead to audible differences doesn't strike me as outlandish.

It's not outlandish at all. But the very fact that it's not outlandish means that it's a proposition that can - and should - be tested. If folks acknowledge the results of such testing, great. If they instead refuse to take notice of it - or discount it based on suspect objections - that's a problem.

 

[Deleted member 48726]

It's not outlandish at all. But the very fact that it's not outlandish means that it's a proposition that can - and should - be tested. If folks acknowledge the results of such testing, great. If they instead refuse to take notice of it - or discount it based on suspect objections - that's a problem.

Does the power cube show frequency response into complex loads?

 

[tmtomh]

Does the power cube show frequency response into complex loads?

@amirm can answer that. Whether you take notice of his answer is another question of course.

 

[Deleted member 48726]

@amirm can answer that. Whether you take notice of his answer is another question of course

Oh, so you didn't know but still used is as an attack in your argument.. Cool.

Just because I don't respond much to your posts doesn't mean I am not interested in meaningful discussion. Actually quite the contrary.

 

[tmtomh]

Oh, so you didn't know but still used is as an attack in your argument.. Cool.

Just because I don't respond much to your posts doesn't mean I am not interested in meaningful discussion. Actually quite the contrary.

It wasn't an attack. It was a description of the discussion so far. As to your question, the Powercube simulates a complex speaker load. But you're never going to take my word for it, so why not have the person who runs this site and does those Powercube tests respond instead? I figure that will increase the chances that you'll take notice of the response (though I still don't think the chances are great).

And you still haven't given anyone an example of Amir "praising bad equipment."

 

[amirm]

Does the power cube show frequency response into complex loads?

Powercube is just the load. It doesn't care what you do with that load. Its impedance though is only calibrated for 1 kHz.

Regardless, your question doesn't make sense as there is no complex load that represents all the speakers people use. In that regard, it is no different than me showing two resistive load frequency responses. That test readily shows load dependency or lack thereof. We don't need to complicate it, pun intended, with a random variable.

 

[amirm]

Oh, so you didn't know but still used is as an attack in your argument.. Cool.

Seems like you missed his point. I have already adopted, at potentially huge expense (power cube as I have it costs $21,000), for something that may not be revealing at all. Even cheap amps are able to pass complex angles at 4 and 8 ohms.

 

[Deleted member 48726]

Powercube is just the load. It doesn't care what you do with that load. Its impedance though is only calibrated for 1 kHz.

Regardless, your question doesn't make sense as there is no complex load that represents all the speakers people use. In that regard, it is no different than me showing two resistive load frequency responses. That test readily shows load dependency or lack thereof. We don't need to complicate it, pun intended, with a random variable.

So 1 kHz impedance test.

It does make sense. I have been proposing the use of representative equivalent circuits a couple of times.
It would have been a lot cheaper than the cube and would show an exact response to a real load (without non linearities).
The money you saved you could've used to take the Panther out for fine dining once a week for a long time.

 

[IPunchCholla]

Racist?? That's harsh. Show me.

I can't. I reported it. And it was deleted.

ETA: You still haven't replied about Amir's recommendations. What's harsh is calling out an entire nation's manufacturing practices, accusing them of fraud, implying Amir goes along with it, and not backing it up with evidence.

 

[HarmonicTHD]

So 1 kHz impedance test.

It does make sense. I have been proposing the use of representative equivalent circuits a couple of times.
It would have been a lot cheaper than the cube and would show an exact response to a real load (without non linearities).
The money you saved you could've used to take the Panther out for fine dining once a week for a long time.

You have no clue what you are talking about do you?

So what values (R, I, C) are you proposing in „your“ equivalent circuit?

How do you ensure the circuit itself doesn’t add distortion? (Hint: why you think the power cube is so expensive?)

Do you think @amirm doesn’t know equivalent circuits? Why did he spend the 21k?

 

[solderdude]

So 1 kHz impedance test.

It's a load test (calibrated at 1kHz) and one that at higher levels (heating up) does not change its values so is low distortion and can provide inductive and capacitive load.

I agree with @amirm , there is no single 'complex load' that would represent most speakers. Nor are there loads that will be equally 'hard' for all amps.
The advantage is that the measurements are comparable and do say something about performance in 2, 4 and 8 ohm. Higher usually isn't a problem, lower is more like a short circuit.

I would prefer to see clipping behavior than complex load behavior as that can be quite complex to do.

That said... the efforts shown here by @pma are to show that amps that perform well with resistive loads may not fair well with certain complex loads.
I applaud that. It isn't representative for other speakers and how amps will react. @pma also clearly mentions that every time.
It also showed that in certain cases the output devices of amps may have a hard time yet don't when loads are resistive. An indicator of why certain amps could die when having a party with loud music while the speaker and amp specs would indicate they should survive.

And one should realize that both ASR and even PMA additional measurements are not 'complete' as even more can be measured.
Basic measurements do tell things (and are comparable when done properly acc. to standards) but may not tell how said amp will work in your home with your speakers and if that is your taste.

And... Amir's recommendations are a personal thing and may not apply to everyone else. They are based on his opinion (measurements and some listening tests) and probably take price into consideration.
Amir might be recommending something that has hidden flaws which may not detected with standard tests and cannot predict longevity. He also sometimes cannot stress test or open up gear that is new from owners so take that into consideration as well when reading the final conclusion.

 

[Deleted member 48726]

It's a resistance test (calibrated at 1kHz) and one that at higher levels (heating up) does not change its values so is low distortion.

I agree with Amir, there is no single 'complex load' that would represent most speakers. Nor are there loads that will be equally 'hard' for all amps.
The advantage is that the measurements are comparable and do say something about performance in 2, 4 and 8 ohm. Higher usually isn't a problem, lower is more like a short circuit.

I would prefer to see clipping behavior than complex load behavior as that can be quite complex to do.

That said... the efforts shown here by @pma are to show that amps that perform well with resistive loads may not fair well with certain complex loads.
I applaud that. It isn't representative for other speakers and how amps will react. @pma also clearly mentions that every time.
It also showed that in certain cases the output devices of amps may have a hard time yet don't when loads are resistive. An indicator of why certain amps could die when having a party with loud music while the speaker and amp specs would indicate they should survive.

Thank you for a non demeaning response. It seems the longer a thread gets the more it attracts foul language and personal attacks.

Of course there is no one fits all circuit. In other threads I like the idea of representative circuits of different severity. The reader can then somewhat gauge the tests and see which impedance /phase traces best suits the speakers he have. Or segments of the trace even, as worst case.

The actual usefulness of the test would be better and the conversion to real life uses would benefit.