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In Reply to: RE: Apparently you've not been reading my posts. posted by morricab on February 24, 2025 at 04:34:35
-why not do proper research on the topic?
I've measured AB amps on the bench. If they are improperly biased and running class B as a result, the crossover artifact is easily seen on the scope and the output level isn't very important. Its also (as you know) easily heard.
So I think we can assume this amp doesn't have that particular problem- users haven't reported it anyway...
So its either AB or Topping figured out a way to get around the problem. And there's evidence for the latter- Topping mentions the amp uses a 'module' of their own design and research. Clearly getting a lot of feedback and a microcontroller to prevent damage is part of it, but is that all? Could it be that they also figured a way to not have expensive heatsinks (which we've established they don't)? What could that way possibly be??
Follow Ups:
USERS ARE NOT EVIDENCE!!! A lot of users like Naim amps and some of the other so-called AB amps that exhibit zero crossing distortion. They likely can't hear worth a damn but that is another discussion...
Thanks for confirming what I have been saying, if an amp is AB or A and properly biased it doesn't have zero crossing distortion... If it is improperly biased and goes into cutoff or non-linear zone then it has zero crossing distortion and is effectively (regardless of mfg. claims) Class B because the bias is too low to keep the devices on through the handoff.
As I said, without a residual plot of the distortion component, we don't know if the Topping has zero crossing distortion or not. User feedback is not evidence.
Amir doesn't provide a residual distortion waveform and so we don't see if it is an issue or not. If it is not, then the Topping is not Class B and if it is there, even if small, then it is a Class B amp.
Honestly, the level of speculation in your responses is frankly amateurish and beneath the level of someone who has been an amp designer for a long time. You have NO idea if the amp has zero crossing distortion or not and the level of noise, distortion, and user feedback is not evidence of anything. Amir's measurements are not indicative either. One thing though is pretty clear is this, if an amp is underbiased then it will exhibit zero crossing distortion and is effectively Class B (even if claimed otherwise). There are no Class B amps that are completely free from this because it is inherent in the physics of the behavior of transistors.
USERS ARE NOT EVIDENCE!!! A lot of users like Naim amps and some of the other so-called AB amps that exhibit zero crossing distortion. They likely can't hear worth a damn but that is another discussion...
Wait- huh? All people that listen to Naim amps can't hear worth a damn?
Your logic is terribly flawed.
If it is improperly biased and goes into cutoff or non-linear zone then it has zero crossing distortion and is effectively (regardless of mfg. claims) Class B because the bias is too low to keep the devices on through the handoff.
The amps you are talking about are not designed for class B. You seem to be ignoring that simple fact. So yes, when improperly biased (and so operating as a class B amp) they will have a problem. But if the circuit is designed to get around that problem with intention of being a class B circuit then your statement is false.
User feedback is not evidence.
Testimony is indeed evidence. What is is not is proof. You seem to be conflating 'evidence' with 'proof'. Do you see the distinction?
If you wish to be abusive that's on you. I hate to come back with something that might be considered abusive as well but in plain English you don't know what you're talking about. I've worked with amps that were operating class B because of insufficient bias and I can tell you they don't reproduce a sine wave properly. You don't need to have them at super low power- the problem shows up because at zero crossing the amp is low power at that point! Amirim's measurements don't show any evidence of a problem; if there was one the sine waves he showed would have been sufficient. Based on your comments though I fear this will be lost on you.
My recommendation is get an amp on which you can adjust the bias and put a scope on it, then adjust the bias and see what I'm talking about. If there's a problem at the zero crossing its pretty audible and you won't need a super low signal level to see in on the 'scope.
You've still not explained how the EV A-20C, which is a class B amp, can have no zero crossing artifact.
"Wait- huh? All people that listen to Naim amps can't hear worth a damn?"
Pretty much yes...same for 99% of the rest of hifi gear that sounds like crap.
Most people are not good critical listeners and the latch on to either advertisement (Naim is good at PRAT) or some specific aspect of the sound they like at the expense of most of the rest.
"The amps you are talking about are not designed for class B. You seem to be ignoring that simple fact. So yes, when improperly biased (and so operating as a class B amp) they will have a problem. But if the circuit is designed to get around that problem with intention of being a class B circuit then your statement is false."
Designed to get around it HOW??? You keep saying that but it doesn't mean that there is a way around it. Naim certainly hasn't found the way around it because they make Class B amps that have zero crossing distortion. If you know how to get around it then demonstrate how you would get around it. The fact that you haven't expressed a single circuit idea on how to do it tells me that YOU DON'T KNOW HOW to do it. Oh, and please provide measurements that demonstrate that it actually worked as claimed...claims aren't what they used to be you know.
User feedback is meaningless. You can always find someone who likes something, no matter how terrible it really is. It is evidence of nothing other than a subjective opinion and you don't know if that is in the minority or majority. You see the difference??
"'ve worked with amps that were operating class B because of insufficient bias and I can tell you they don't reproduce a sine wave properly. You don't need to have them at super low power- the problem shows up because at zero crossing the amp is low power at that point! Amirim's measurements don't show any evidence of a problem; if there was one the sine waves he showed would have been sufficient. Based on your comments though I fear this will be lost on you."
It's sad that you think a professional challenge is abusive. Stop being a snowflake Ralph and man up. You keep ignoring my point that Amir's measurements don't show the residual distortion in the sine wave plot. With low distortion amps the high level sine wave will never look distorted, you have to extract out the residual distortion and plot it like Stereophile does (so, we know it's possible but curiously Amir doesn't do it) and then you can see if there is zero crossing distortion. Until then there is no proof one way or the other. The fact that STereophile gets this and you don't seem to get it makes me wonder what you have really learned in 40 years of amp designing. Measurements don't seem to be your strong suit.
https://www.stereophile.com/content/naim-classic-200-series-nap-250-power-amplifier-measurements
Please refer to Figure 7 to illustrate what I am referring to. You see the residual distortion plot shows the zero crossing distortion in this Naim amp. No such plot was provided for the Topping.
"You've still not explained how the EV A-20C, which is a class B amp, can have no zero crossing artifact."
Explain what? You have not provided any evidence that this is in fact true. I cannot explain something that has not be demonstrated to exist. When you can do that, then perhaps there is something to discuss here.
"My recommendation is get an amp on which you can adjust the bias and put a scope on it, then adjust the bias and see what I'm talking about. If there's a problem at the zero crossing its pretty audible and you won't need a super low signal level to see in on the 'scope."
I have first-hand experience with a Plinius SA-103, which has a Class AB and Class A bias setting (push of a button on the front panel). The sound quality difference is very significant and the measurements on Stereophile show clearly the effect of the AB setting vs. the A setting.
https://www.stereophile.com/content/plinius-audio-sa-103-power-amplifier-measurements
It's sad that you think a professional challenge is abusive. Stop being a snowflake Ralph and man up.
Name calling like this is abusive and earlier you used the word 'amateurish'. What is sad is that you have to resort to this sort of tactic. It literally means you have nothing.
I explained how a solid state class B amp can be designed to have no zero crossing artifact. My assumption is you didn't read that post or have chosen to ignore it.
You have not provided any evidence that this is in fact true. I cannot explain something that has not be demonstrated to exist.
I did ask what sort of evidence would be acceptable but you didn't respond.
Furthermore, the EV A-20C is a tube amp, not a transistor amp. Tubes behave differently around cutoff than transistors, which get really non-linear. It could be that a tube amp in Class B is not as troubled by zero crossing distortion as a transistor amp clearly is. Therefore, it is unfair to use that as an example when discussing transistor amps.
This sure looks like backpedaling to me... I explained how its able to have no zero crossing artifact. Clearly you're not reading.
Robert Heinlein once said "Ignorance is curable, stupid is forever."
If one refuses to read, and therefore chooses to remain ignorant, how is that not stupid??
It means you have offered nothing and then acted offended when challenged...you can say that is name calling but it is a fact.
"You have not provided any evidence that this is in fact true. I cannot explain something that has not be demonstrated to exist.
I did ask what sort of evidence would be acceptable but you didn't respond."
Not true. I told you that the residual distortion wave form would be proof. You didn't provide that for either the Topping or the old EV amp.
"This sure looks like backpedaling to me... I explained how its able to have no zero crossing artifact. Clearly you're not reading."
No, clearly we were discussing transistor amps in the thread and then you chose to throw something else into the mix.
"Robert Heinlein once said "Ignorance is curable, stupid is forever.""
Project much?? You're the one who misinterpreted what the thread was discussing and decided to throw some old tube amp into the mix. I read your posts but didn't google the exact amp until recently. You still didn't provide any technical proof that it doesn't suffer from crossover distortion. WHat few measurements I found would not tell you this.
So, it is you who are dodging the requests for data to demonstrate.
Did you miss the point that the Topping is a solid state amp?
You're the one who misinterpreted what the thread was discussing and decided to throw some old tube amp into the mix.
I didn't misinterpret anything. Here is the text again:
https://www.audioasylum.com/forums/amp/messages/25/254430.html
I explained what was different about that amp and so it became relevent.
I also explained how a class B solid state amp can get around the problem you described. But you didn't read that.
I also asked for what would be considered 'proof' since its pretty obvious that if I just put up a nice looking sine wave you would challenge its source. I'm not playing that game.
No dodging anything; just dealing with the fact that you tend to obfuscate when presented with the truth of technical things about which you don't have training or experience.
Some old tube circlotron design is IRRELEVANT to a discussion about Class B solid state amps. I showed you examples of Class B commercial amps that clearly demonstrate zero crossing distortion. You just keep using words!
You can't even show me evidence that your one example doesn't exhibit the zero crossing distortion issue. Not one piece of evidence from you! Claims are just that...claims. I have showed you numerous examples of underbiased AB and B amps (class B is by definition underbiased so that the transistors go into cutoff) that exhibit the issue.
On top of that I tell you clearly what is missing from the Topping measurements that would confirm it to have or not have zero crossing distortion and then you pretend I didn't tell you what was missing! Who isn't reading?? Clearly you.
I've mentioned several times how a solid state amp can be designed to avoid crossover or notch distortion.
You're not interested so around and around we go...
You need to showed data, your explanation is worthless without data to prove your claim.
I guess you would rather play the victim while projecting...
Furthermore, the EV A-20C is a tube amp, not a transistor amp. Tubes behave differently around cutoff than transistors, which get really non-linear. It could be that a tube amp in Class B is not as troubled by zero crossing distortion as a transistor amp clearly is. Therefore, it is unfair to use that as an example when discussing transistor amps. I don't actually know of any current commercial tube amps that are Class B for comparison.
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