I know people with very high end systems who are honest enough to admit they can't hear image depth.It seems that is an ability you either have or don't have .Much like those "magic" picture puzzles in which some people see a 3D image straight away ,some have to focus for a while before they see it and then some never see it.Also a bit like colour blindness.
Hi Mark,
Hi jtgofish,
Image depth has a lot to do with how our mind places imagination into the mix and fills in information it expects to be there. So many things impact what is called imaging.
Absolutely, and that shows up on measurements. This boils down to using the correct part in an application, and making engineering choices.
Hi jtgofish,
Image depth has a lot to do with how our mind places imagination into the mix and fills in information it expects to be there. So many things impact what is called imaging.
👍
This is the kind of stuff that hysteresis distortion seems to do. It's never visible in isolation because it's only ever activated if there's a sufficiently strong signal at the same time. The problem I have with @anatech 's claim that the available measurement resolutions are higher than our hearing ability, is that I haven't seen anyone with a firm grip on the middle area, say, a modest 60-80dB below the signal peaks, which should be easy, but it obviously isn't.
Impulse and step responses, on a linear time scale, generally struggle to achieve more than 1000 pixels of vertical resolution, or 60dB.
Then people switch over to frequency plots and boast that the noise floor is ~120dB below. Except that they're now measuring completely different things.
Transient ripples, glitches and clicks, in the -60 to -80dB region, could be visible as 1-10 pixels on a linear graph with an almost unbelievable 10k vertical resolution. But who does that?
Hi abstract,
-80 dB from 1 watt (2.73 VAC) is about 2/3 scale down to the noise floor. Everything is plainly visible at those levels. Seeing that stuff is trivial. I'm running a signal at 2.73 VAC out for power amps into an 8R load. FFT analysis allows us to see everything around it. For preamps, I run a tough 1 Vrms signal since 0 dB for signal is roughly -10 dBu (0.316 Vrms).
I also run tests with no signal to see general noise and power supply issues.
Impulse testing is typically done with acoustic products. Oscilloscopes are normally used as a transient, by definition, generates all frequencies at once. That is you should know. You can't really test as you are suggesting, the tools are incorrect for this. Therefore, we are stuck using an oscilloscope for tone bursts or any other discontinuous signal.
An impulse test would only show problems with electronic equipment if you either overloaded it, or it was a spectacularly poorly designed product. You're going down the same path as the debunked TIM thought process.
-80 dB from 1 watt (2.73 VAC) is about 2/3 scale down to the noise floor. Everything is plainly visible at those levels. Seeing that stuff is trivial. I'm running a signal at 2.73 VAC out for power amps into an 8R load. FFT analysis allows us to see everything around it. For preamps, I run a tough 1 Vrms signal since 0 dB for signal is roughly -10 dBu (0.316 Vrms).
I also run tests with no signal to see general noise and power supply issues.
Impulse testing is typically done with acoustic products. Oscilloscopes are normally used as a transient, by definition, generates all frequencies at once. That is you should know. You can't really test as you are suggesting, the tools are incorrect for this. Therefore, we are stuck using an oscilloscope for tone bursts or any other discontinuous signal.
An impulse test would only show problems with electronic equipment if you either overloaded it, or it was a spectacularly poorly designed product. You're going down the same path as the debunked TIM thought process.
Yes, I realise that 😀
I used that to indicate something was changing, rather than a steady state waveform!
Possible some organ music can be considered steady state, in parts, but anything percussive is perhaps more noticeable.
Having said that, the start and stop of notes on for example, Bach's Toccata, are perhaps also important.
You mention a 'normal' or 'good' amplifier, can you please define that?
In my experience all amplifiers are non linear, some in more audibel ways than others.
The GNFB then attempts to straighten them out, with varying degrees of success.
The more linear the amplifier, the better job GNFB can do, yes?
Lynn's viewpoint in his article is that the harmonics generated (by the non linearity) go around and around, being multiplied each time by the non-linear bit in the middle, thus 'spreading out' the distortion, if I understand correctly, rather than elimminating it.
Obviously the physical components are the same, but we can look at them in different ways. The temporal view:
The distortions will always appear at the output (else how could they be fed back?) to a slightly later point in time (well, the delay is primarily in the amplifier, not the wire), to correct the input... that then eventually arrives at the output again. This is the 'what's going on here' view, naive perhaps, but as the FR of the amplifier is limited, perhaps not too far from reality.
So the question is, can a non-linear, but GNFB corrected amplifier, create different distortion artifacts with different signals? If so, the imaging will surely be affected, yes? My suggestion is that with GNFB there's more 'chatter' with the corrections whizzing round and round, and thus the character of the amplifier in the face of transients may vary more than in an amplifier without GNFB, where the signal only traverses the amplifier once.
I'm not against feedback, my favourite tube amp has lots of it between the driver and power tube (with the input tube using local feedback), and the OPT left out in the cold.. it's not ideal, but it is very very fast...
... but I do find GNFB lazy and boring 😀, and has various hidden problems of this harmonic multiplication that I don't consider helps the sound. There must be a better way.
Or perhaps, the imaging 😀
Anyway, I hope that clarifies my suggestion.
Hi Globulator,
Firstly, in electronic terms, a sine wave is constantly changing and is by no means a constant signal. You have to think in terms of the speed electronic circuits operate. The idea that a sine wave of constant amplitude is a constant signal is the result of the way people who don't understand electronics well think. A constant signal is a DC level.
Circuits deal with signals in the instant, or moment. The circuit has no idea where the amplitude will go next at any given moment. It just reacts in the instant, period. So a sine wave exercises the circuit over the entire amplitude range the peak value represents. It is no easier or difficult than any other signal or combination of signals.
Every amplifier has non-linearity to some degree. Feedback helps correct this by comparing the output with the input next to instantly. In audio terms, it is instant. No transient distortion exists. A good amplifier has a minimal amount of distortion and good output characteristics. But you can't design a poorly behaving, non-linear circuit and expect feedback to fix it. So if your output stage is more linear, you will have lower distortion than one that isn't as linear.
As I said, distortion and correction is instant, but only to a degree. Distortion never goes "around and around". Non-linearity is corrected in an instant to whatever level it can be, then it's over as in the next instant the signal is entirely new. If you have IMD distortion, harmonic distortion will cause those frequencies to repeat. It could look like a "spray" on the display, but it is an instantaneous thing. The more feedback you have, the greater distortion can be reduced as long as the circuit remains stable. Of course you can also pick up noise from other sources as well.
Feedback doesn't make anything lazy. If anything, well designed amplifiers using feedback are very dynamic sounding. There is something else going on, or it is an imagined effect.
Remember, feedback happens instantly in audio terms. It happens equally across amplitude (it doesn't compress any signal such as your description suggests). Feedback drops as frequency increases giving rise to higher distortion. That's why I test IMD at 19 and 20 KHz. So here you have demonstrated proof that feedback reduces distortion. The more feedback you have, the more you can afford to lose at higher frequencies and still have a low distortion signal. Feedback also lowers output impedance and power supply noise rejection. That is unless the designer messed something up.
The slowest transistor used in audio amplifiers responds well past 1 MHz. The smaller ones past 200 MHz or higher often enough. Compare this with 100 KHz, and the audio range that runs to an accepted 20 KHz. We limit the frequency response electronically (compensation) to keep the amplifier stable. We also limit the input frequency range because signals above 20 KHz are just noise. Learn to think in terms of microseconds and you'll understand these circuits much better. Once you can do that, many ideas put forward clearly can't be true and don't make sense.
Read Bob Cordell or Douglas Self for a better understanding. What they have written works in practice, it isn't just a thought experiment. In short, they are correct. Others don't actually work successfully in the audio field, so why would you listen to what they have to say?
-Chris
Firstly, in electronic terms, a sine wave is constantly changing and is by no means a constant signal. You have to think in terms of the speed electronic circuits operate. The idea that a sine wave of constant amplitude is a constant signal is the result of the way people who don't understand electronics well think. A constant signal is a DC level.
Circuits deal with signals in the instant, or moment. The circuit has no idea where the amplitude will go next at any given moment. It just reacts in the instant, period. So a sine wave exercises the circuit over the entire amplitude range the peak value represents. It is no easier or difficult than any other signal or combination of signals.
Every amplifier has non-linearity to some degree. Feedback helps correct this by comparing the output with the input next to instantly. In audio terms, it is instant. No transient distortion exists. A good amplifier has a minimal amount of distortion and good output characteristics. But you can't design a poorly behaving, non-linear circuit and expect feedback to fix it. So if your output stage is more linear, you will have lower distortion than one that isn't as linear.
As I said, distortion and correction is instant, but only to a degree. Distortion never goes "around and around". Non-linearity is corrected in an instant to whatever level it can be, then it's over as in the next instant the signal is entirely new. If you have IMD distortion, harmonic distortion will cause those frequencies to repeat. It could look like a "spray" on the display, but it is an instantaneous thing. The more feedback you have, the greater distortion can be reduced as long as the circuit remains stable. Of course you can also pick up noise from other sources as well.
Time, the scale of time is your problem here. Think instantaneous. The frequencies presented to the circuit are much lower than the response of the circuit. In other words, audio circuits are much faster than the signals you are amplifying. I think this is where confusion comes in. The circuit reacts a lot more quickly than any signal it will process. This is the exact same thinking as TIM distortion, and doesn't happen for the same exact reasons.
Not the way you are thinking. I do IMD tests with 19 KHz and 20 KHz signals of equal amplitude. Pretty much worst case for audio amplifiers. The distortion mechanism is identical no matter what you feed in. The circuit will distort the same way with different products no matter which signals you apply. Good amplifiers produce so little distortion that you can't hear them. Bad ones create distortion you can hear and it is all easily tested.
Feedback doesn't make anything lazy. If anything, well designed amplifiers using feedback are very dynamic sounding. There is something else going on, or it is an imagined effect.
Remember, feedback happens instantly in audio terms. It happens equally across amplitude (it doesn't compress any signal such as your description suggests). Feedback drops as frequency increases giving rise to higher distortion. That's why I test IMD at 19 and 20 KHz. So here you have demonstrated proof that feedback reduces distortion. The more feedback you have, the more you can afford to lose at higher frequencies and still have a low distortion signal. Feedback also lowers output impedance and power supply noise rejection. That is unless the designer messed something up.
The slowest transistor used in audio amplifiers responds well past 1 MHz. The smaller ones past 200 MHz or higher often enough. Compare this with 100 KHz, and the audio range that runs to an accepted 20 KHz. We limit the frequency response electronically (compensation) to keep the amplifier stable. We also limit the input frequency range because signals above 20 KHz are just noise. Learn to think in terms of microseconds and you'll understand these circuits much better. Once you can do that, many ideas put forward clearly can't be true and don't make sense.
Read Bob Cordell or Douglas Self for a better understanding. What they have written works in practice, it isn't just a thought experiment. In short, they are correct. Others don't actually work successfully in the audio field, so why would you listen to what they have to say?
-Chris
Not everything. Do I have to fire up Audacity and give examples to prove that you can have a signal that is full-scale in the time domain but doesn't reach anywhere near full scale on an FFT? Specks of dust hitting a phono needle could cause loud, easily audible and visible glitches, but it will barely touch the noise floor on an FFT.
An example of "feedback" is the bootstrap. Audio practice shows that this circuit audibly degrades the signal. That recognize and to regard this would be audio!
By the way: If we talk about audio and would observe the simplest scientific standards, then first the observation, the hearing, audio - also a measuring process. Then the attempt to record this observation by means of further, other measuring procedures. And we also have to make sure that we measure what we claim to measure. So we also have to carry out a test via control experiments and so on. And then there's also the analysis of context and complexity - aside: I don't know of any study in the audio field that takes this into account. Unfortunately, there are quite a few audio "engineers" who claim not to hear, i.e. not to hear contrastively, but to assess their non-observation in terms of gaze measurements. And call this "engineering" or science.
Many focus on the signal noise ratio, for example. But where does any of the supposedly determined noise appear?
By the way: If we talk about audio and would observe the simplest scientific standards, then first the observation, the hearing, audio - also a measuring process. Then the attempt to record this observation by means of further, other measuring procedures. And we also have to make sure that we measure what we claim to measure. So we also have to carry out a test via control experiments and so on. And then there's also the analysis of context and complexity - aside: I don't know of any study in the audio field that takes this into account. Unfortunately, there are quite a few audio "engineers" who claim not to hear, i.e. not to hear contrastively, but to assess their non-observation in terms of gaze measurements. And call this "engineering" or science.
Many focus on the signal noise ratio, for example. But where does any of the supposedly determined noise appear?
Attachments
Hi abstract,
An FFT is a mathematical process that depends on multiple samples, therefore it is insensitive to what you pointed out. In other words, you are using the wrong tool. I tried to tell you that earlier.
Look, if you aren't going to assess problems using the correct tools and methods, and then point out why they are totally ineffective, that's your problem. A good researcher / engineer / tech knows what tools are appropriate in different situations. So instead of trying to find fault, why not learn the proper way to investigate issues? It's real easy to throw stones, much more difficult to actually learn.
As I have said continuously over my time here, we measure and listen. Our tools include our ears plus just about every other instrument. The other thing that has been pointed out constantly is that our ears are not calibrated, and they are anything but consistent. Our memories are highly variable as well. So using only your hearing is like travelling through the world without a compass or GPS. The worst products I have ever seen were "designed by ear".
Hi cumbb,
You're too general. A bootstrap has many variables and the capacitor crowd would have a field day with this. My comments above address your "scientific standards". The equipment you reference to is unstable, unreliable but can give good immediate comparative results - but not always. The gooey thing between your ears will interfere with a nasty defect called "expectation bias".
Circuit performance depends both on design and execution. Some circuits are better than others for sure.
At this juncture, I'll merely point out that the authors I referenced above work in the audio industry, and Douglas Self is an award winning engineer who designs top equipment. Probably not someone you are familiar with since he is not interested in fame but rather performance. His designs were used creating the music you listen to. Do some research and try to learn something.
A guide who has never had a compass will say you don't need one. After you introduce the guide to it, it would be indispensable for them. The same holds true for really good audio test equipment. Once you can see what is really going on, it changes things. Yes, there is a cost of admission. Without being able to see the truth you are truly in the dark.
An FFT is a mathematical process that depends on multiple samples, therefore it is insensitive to what you pointed out. In other words, you are using the wrong tool. I tried to tell you that earlier.
Look, if you aren't going to assess problems using the correct tools and methods, and then point out why they are totally ineffective, that's your problem. A good researcher / engineer / tech knows what tools are appropriate in different situations. So instead of trying to find fault, why not learn the proper way to investigate issues? It's real easy to throw stones, much more difficult to actually learn.
As I have said continuously over my time here, we measure and listen. Our tools include our ears plus just about every other instrument. The other thing that has been pointed out constantly is that our ears are not calibrated, and they are anything but consistent. Our memories are highly variable as well. So using only your hearing is like travelling through the world without a compass or GPS. The worst products I have ever seen were "designed by ear".
Hi cumbb,
You're too general. A bootstrap has many variables and the capacitor crowd would have a field day with this. My comments above address your "scientific standards". The equipment you reference to is unstable, unreliable but can give good immediate comparative results - but not always. The gooey thing between your ears will interfere with a nasty defect called "expectation bias".
Circuit performance depends both on design and execution. Some circuits are better than others for sure.
At this juncture, I'll merely point out that the authors I referenced above work in the audio industry, and Douglas Self is an award winning engineer who designs top equipment. Probably not someone you are familiar with since he is not interested in fame but rather performance. His designs were used creating the music you listen to. Do some research and try to learn something.
A guide who has never had a compass will say you don't need one. After you introduce the guide to it, it would be indispensable for them. The same holds true for really good audio test equipment. Once you can see what is really going on, it changes things. Yes, there is a cost of admission. Without being able to see the truth you are truly in the dark.
Douglas Self is an example: calling a book audio design does not mean that audio design is included. Most of these circuits would have no place in audio. I think the "expectation bias" you mentioned also apply here too;-)
He should have used some practical experience and experiments to define the scope for the concepts circuits to be discussed. These practical experiences and experiments would have referred to the ability of the ear, audio, for example, that electronic parts, such as resistors, transistors, capacitors, audibly modulate the sound, in contrast to the concepts taught, represented in lines and numbers. And many parts modulate a lot;-)-; And different parts modulate very different;-)-;
You do NOT measure per peeking this. This may be in contrast to your "expectation bias" too.
He should have used some practical experience and experiments to define the scope for the concepts circuits to be discussed. These practical experiences and experiments would have referred to the ability of the ear, audio, for example, that electronic parts, such as resistors, transistors, capacitors, audibly modulate the sound, in contrast to the concepts taught, represented in lines and numbers. And many parts modulate a lot;-)-; And different parts modulate very different;-)-;
You do NOT measure per peeking this. This may be in contrast to your "expectation bias" too.
Hi cumbb,
I'm sorry. You really don't seem to get it at all. The man is an expert in the field. After reading some of your posts, you really need to educate yourself.
Go ahead, crush semiconductors on heat sinks (BTW, semi manufacturers have recommended mounting methods and pressures to maximize heat transfer).
Experiments have been done by myself (at a very beginner level compared to others). The engineering community has experimented with all theory and have proved them through practical results. But I guess you know better.
None of this is debatable. What you need to do is educate yourself.
As for parts, yep. I have studied individual parts since the 1970's. I have testing equipment and jigs on my bench in daily use and have always had them. They have improved with advances in instrumentation. Nothing you just mentioned is news to anyone in the industry. Also, we can measure parts and tell what distortion mechanisms exist, and where in circuits they will impact performance. Today I find listening to equipment merely a confirmation and maybe sanity test. My own equipment has benefited substantially from everything I have learned thanks to Doug Self and others. Romance is in the physical appearance, deep satisfaction in the performance.
I'm sorry. You really don't seem to get it at all. The man is an expert in the field. After reading some of your posts, you really need to educate yourself.
Go ahead, crush semiconductors on heat sinks (BTW, semi manufacturers have recommended mounting methods and pressures to maximize heat transfer).
Experiments have been done by myself (at a very beginner level compared to others). The engineering community has experimented with all theory and have proved them through practical results. But I guess you know better.
None of this is debatable. What you need to do is educate yourself.
As for parts, yep. I have studied individual parts since the 1970's. I have testing equipment and jigs on my bench in daily use and have always had them. They have improved with advances in instrumentation. Nothing you just mentioned is news to anyone in the industry. Also, we can measure parts and tell what distortion mechanisms exist, and where in circuits they will impact performance. Today I find listening to equipment merely a confirmation and maybe sanity test. My own equipment has benefited substantially from everything I have learned thanks to Doug Self and others. Romance is in the physical appearance, deep satisfaction in the performance.
Unfortunately, this is a forum where everyone has to proof and assess things for themselves. If we were a room with 100 people conducting and interpreting experiments together, it would no longer be possible to talk our way out of it. Then it would also become clear whether someone really can't hear, or defiant doesn't want to hear: "No, I learned draw lines by numbers, and that's all I want to do!"-)
True, however if you fly in the face of known facts by professionals in the field instead of learning (or even attempting to learn), you are pretty much accepting ignorance as a way of life.
Discoveries made in garages no longer occur. We've gone far past that now. HP started in a small garage by two people. Do you think any test and measurement company could possibly start in similar conditions? No, because what we know and is standard practice has progressed to a point where you nee specialized equipment and teams of people to move forward.
The same holds true for something like an audio company. You need the resources and the collective brain trust to do it well. Otherwise what you have is an ego and a story to support it. I've met many of those people over the years.
If you want to throw dust in the air to cloud issues in an effort to generate doubt, you're only hurting yourself and others trying to learn.
Anyway, as I have said consistently over the years, measurements do correlate with subjective opinion. As measurements became better and more understood, the more closely aligned subjective opinion became to measured data. There is only one group that won't accept this. Those without the ability to measure and understand. The people with too much ego to accept their hearing abilities are not consistent enough to be a clear guide if they are honest. The human body and mind simply isn't designed for this.
I've no problem with anyone experimenting. I would encourage it. However, you have to recognise the limitations of your experiment and your equipment. Controlling variables is a challenging part of experimentation. If you can't do that, you have no results you can rely on. Same for the limitations of any equipment. You may be correct that you can't measure what you can hear, but many can and do routinely. I do it every day. I've spent over 40 years doing this.
Discoveries made in garages no longer occur. We've gone far past that now. HP started in a small garage by two people. Do you think any test and measurement company could possibly start in similar conditions? No, because what we know and is standard practice has progressed to a point where you nee specialized equipment and teams of people to move forward.
The same holds true for something like an audio company. You need the resources and the collective brain trust to do it well. Otherwise what you have is an ego and a story to support it. I've met many of those people over the years.
If you want to throw dust in the air to cloud issues in an effort to generate doubt, you're only hurting yourself and others trying to learn.
Anyway, as I have said consistently over the years, measurements do correlate with subjective opinion. As measurements became better and more understood, the more closely aligned subjective opinion became to measured data. There is only one group that won't accept this. Those without the ability to measure and understand. The people with too much ego to accept their hearing abilities are not consistent enough to be a clear guide if they are honest. The human body and mind simply isn't designed for this.
I've no problem with anyone experimenting. I would encourage it. However, you have to recognise the limitations of your experiment and your equipment. Controlling variables is a challenging part of experimentation. If you can't do that, you have no results you can rely on. Same for the limitations of any equipment. You may be correct that you can't measure what you can hear, but many can and do routinely. I do it every day. I've spent over 40 years doing this.
Hi ! It's logicaly, but does not seen on standart measurements. I don't believe in magic
Right! Logic and everything obeys the laws of physics, electronics being a subset.
What "standard measurements" are depends greatly on the area of the world and common in that industry. Even if you perform the same measurements with the same or similar equipment and conditions, interpreting the results can vary greatly with the people running the tests.
My most used tool is the FFT up to above 90 KHz using an audio analyzer. Of course I use everything else at my disposal depending on what I need to find out. Every day you learn something new, so you keep an open mind. By the same token, things that have been proved and demonstrated you accept unless you have direct conflicts in your results. Then you recheck everything in your test! lol!
What "standard measurements" are depends greatly on the area of the world and common in that industry. Even if you perform the same measurements with the same or similar equipment and conditions, interpreting the results can vary greatly with the people running the tests.
My most used tool is the FFT up to above 90 KHz using an audio analyzer. Of course I use everything else at my disposal depending on what I need to find out. Every day you learn something new, so you keep an open mind. By the same token, things that have been proved and demonstrated you accept unless you have direct conflicts in your results. Then you recheck everything in your test! lol!
A law of physics: everything and everyone takes the path of least resistance;-)
It is not logical, nor science, nor physics, not to measure what I have to measure. And: physics lies elsewhere.
The claim that these stare-"measurements" correspond to what we have to measure is mainly made by electronics engineers with common training. Audio was not even a topic in their training. HF or LF amplifiers were. In other words, amplifiers that visually reproduce one or two or three frequencies as a line, somewhat unchanged. Has nothing to do with audio.
The audio sector is also full of unverified myths and claims. And names also play a role, as in other discourses. But this only prevents proofing and discussion. An example: "Einstein". And no one looks and notices that he made a methodological mistake right at the beginning of his SRT: he only allowed one of the two necessary observers to observe. Everything from here on is pure nonsense. Apparently proven "black holes" and whatnot are misinterpretations of some observations. An example of how easy it is to get the biggest nonsense into almost everyone's heads;-)
It remains #129
It is not logical, nor science, nor physics, not to measure what I have to measure. And: physics lies elsewhere.
The claim that these stare-"measurements" correspond to what we have to measure is mainly made by electronics engineers with common training. Audio was not even a topic in their training. HF or LF amplifiers were. In other words, amplifiers that visually reproduce one or two or three frequencies as a line, somewhat unchanged. Has nothing to do with audio.
The audio sector is also full of unverified myths and claims. And names also play a role, as in other discourses. But this only prevents proofing and discussion. An example: "Einstein". And no one looks and notices that he made a methodological mistake right at the beginning of his SRT: he only allowed one of the two necessary observers to observe. Everything from here on is pure nonsense. Apparently proven "black holes" and whatnot are misinterpretations of some observations. An example of how easy it is to get the biggest nonsense into almost everyone's heads;-)
It remains #129
Hi cumbb,
Actually, no. The right thing to do is seldom the easiest. Grasping at straws is easy. Finding the truth isn't. We follow the evidence, always questioning if there is a better way and thinking about what we experience.
I can see very clearly you have no actual training in engineering or electronics. Of course without understanding you'll try to throw doubt at everything. All you are doing is throwing out questions at things we have all examined and travelled before.
Basically I guess you're of the mind that nothing is known, it's all a mystery. That thinking belongs in the early days. I'm not going to waste any more time on you. Go learn something.
Actually, no. The right thing to do is seldom the easiest. Grasping at straws is easy. Finding the truth isn't. We follow the evidence, always questioning if there is a better way and thinking about what we experience.
I can see very clearly you have no actual training in engineering or electronics. Of course without understanding you'll try to throw doubt at everything. All you are doing is throwing out questions at things we have all examined and travelled before.
Basically I guess you're of the mind that nothing is known, it's all a mystery. That thinking belongs in the early days. I'm not going to waste any more time on you. Go learn something.
I no longer worry about amplifiers! And I used to build them myself... I leave it to the professionals.
No-one ever regretted buying a Rotel Amplifier. Or was it an IBM Computer? 🤣
Rotel have been building essentially the same AB output circuit for about 40 years, and it still wins those VERY dubious HiFi of the Year awards:
It's remarkably similar to Douglas Self's Blameless Amplifier:
http://douglas-self.com/ampins/dipa/dipa.htm
I like to see care taken with Common Mode Rejection Ratio at the differential input, and that can get tricky with volume and tone controls, but the rest is old hat really.
Balance the input topology to reduce noise from the Earth Rail:
You don't need to be Einstein to follow that. 🙂
No-one ever regretted buying a Rotel Amplifier. Or was it an IBM Computer? 🤣
Rotel have been building essentially the same AB output circuit for about 40 years, and it still wins those VERY dubious HiFi of the Year awards:
It's remarkably similar to Douglas Self's Blameless Amplifier:
http://douglas-self.com/ampins/dipa/dipa.htm
I like to see care taken with Common Mode Rejection Ratio at the differential input, and that can get tricky with volume and tone controls, but the rest is old hat really.
Balance the input topology to reduce noise from the Earth Rail:
You don't need to be Einstein to follow that. 🙂
Rotel is very reliable, I'll give them that. I only have 2 comments about our old one (running continuously for over 20 years, btw.)
1, the old-school toroidal block seems to have a tendency to occasionally throw circuit breakers. It might be possible to leave the ferrite in a magnetized state when the relays switch off.
2, The tone. Spare me, j/k. To be perfectly honest I always hated it slightly, through multiple iterations of passive and later active crossovers. Over time, it was always good enough for HT, and remained that way as a motivator to build something "more serious" and easier on the ears.
1, the old-school toroidal block seems to have a tendency to occasionally throw circuit breakers. It might be possible to leave the ferrite in a magnetized state when the relays switch off.
2, The tone. Spare me, j/k. To be perfectly honest I always hated it slightly, through multiple iterations of passive and later active crossovers. Over time, it was always good enough for HT, and remained that way as a motivator to build something "more serious" and easier on the ears.