|
|
Post by marcl on Jun 22, 2023 15:28:48 GMT -5
The problem is this... Audio amplifiers are a bit too complicated to compare accurately using one or two simple measurements. Therefore, attempting to do so, or imagining that you have done so, is unlikely to produce accurate results. (And, if you place excessive confidence in the results, they may also lead you to inaccurate and misleading conclusions.) 1. Most folks in the industry agree that THD and S/N are the two most significant measurements. Therefore, arguably, if you were to only have a single measurement, SINAD wouldn't be that bad of a choice. However, there are a lot of other things you can measure, and not everyone agrees on how important many of the others are. 2. As with many other things, when it comes to audio measurements, there are thresholds of audibility and practical limits. For example, while the specific numbers are still debated, everyone I know agrees that there are limits of audibility for both THD and S/N. That means that there are limits below which they are inaudible... so there is no real benefit of improving them beyond those limits. For example, most people I know agree that , undermost circumstances, an amplifier with 5% THD will probably sound worse than one with 0.5% THD. But most people I know also agree that "nobody can possibly hear the difference between 0.05% THD and 0.005% THD". And, likewise, once the S/N of a system is significantly better than your source material, you really cannot get any practical improvement much beyond that. (And, if you hear a difference between two amplifiers, both of which have THD and S/N well beyond those limits, then it's probably for some OTHER reason.) 3. The upshot of all this is that we often do tend to hear differences between amplifiers. And we often hear those differences in amplifiers whose basic measurements "are good enough that they should sound equally perfect". Therefore, either we're imagining that difference, or it's being caused by something else that we didn't measure. However, considering how many things we didn't measure, and how complex human hearing really is, that last possibility isn't at all unlikely. BUT WE WILL NEVER KNOW THAT THEY SOUND DIFFERENT TO BEGIN WITH IF WE NEVER LISTEN TO THEM.Everyone likes simple answers... So everyone likes simple questions... But they just aren't always good enough to get the job done properly... As the famous quote usually attributed to Albert Einstein goes: “Everything should be made as simple as possible, but not simpler” Amir does all those measurements and more. He typically elaborates on each measurement. SINAD is basically a rating reference in regards to other units tested. Russ Something that I wonder about and I don't ever hear discussed .... what about a given amplifier's ability to deliver power, to deliver current through the wire, with respect to time? What I mean by this is that amplifier measurements are done in some steady state condition. But what happens in very short instants when the source demands a lot of power for a transient? Can two amplifiers with similar SINAD and steady state power ratings differ significantly (due to their design) in how they respond to power demands? And if so, does the distortion profile change in some nonlinear way when one amplifier delivers a short peak of power vs another? Being a Magnepan owner I always hear I should use "high current" amplifiers ... but there doesn't seem to be a technical standard for how to determine this capability. And once again, could two amplifiers capable of the same peak current output have different distortion characteristics at that peak? |
|
|
|
Post by monkumonku on Jun 22, 2023 17:33:35 GMT -5
The problem is this... Audio amplifiers are a bit too complicated to compare accurately using one or two simple measurements. Therefore, attempting to do so, or imagining that you have done so, is unlikely to produce accurate results. (And, if you place excessive confidence in the results, they may also lead you to inaccurate and misleading conclusions.) 1. Most folks in the industry agree that THD and S/N are the two most significant measurements. Therefore, arguably, if you were to only have a single measurement, SINAD wouldn't be that bad of a choice. However, there are a lot of other things you can measure, and not everyone agrees on how important many of the others are. 2. As with many other things, when it comes to audio measurements, there are thresholds of audibility and practical limits. For example, while the specific numbers are still debated, everyone I know agrees that there are limits of audibility for both THD and S/N. That means that there are limits below which they are inaudible... so there is no real benefit of improving them beyond those limits. For example, most people I know agree that , undermost circumstances, an amplifier with 5% THD will probably sound worse than one with 0.5% THD. But most people I know also agree that "nobody can possibly hear the difference between 0.05% THD and 0.005% THD". And, likewise, once the S/N of a system is significantly better than your source material, you really cannot get any practical improvement much beyond that. (And, if you hear a difference between two amplifiers, both of which have THD and S/N well beyond those limits, then it's probably for some OTHER reason.) 3. The upshot of all this is that we often do tend to hear differences between amplifiers. And we often hear those differences in amplifiers whose basic measurements "are good enough that they should sound equally perfect". Therefore, either we're imagining that difference, or it's being caused by something else that we didn't measure. However, considering how many things we didn't measure, and how complex human hearing really is, that last possibility isn't at all unlikely. BUT WE WILL NEVER KNOW THAT THEY SOUND DIFFERENT TO BEGIN WITH IF WE NEVER LISTEN TO THEM.Everyone likes simple answers... So everyone likes simple questions... But they just aren't always good enough to get the job done properly... As the famous quote usually attributed to Albert Einstein goes: “Everything should be made as simple as possible, but not simpler” Something that I wonder about and I don't ever hear discussed .... what about a given amplifier's ability to deliver power, to deliver current through the wire, with respect to time? What I mean by this is that amplifier measurements are done in some steady state condition. But what happens in very short instants when the source demands a lot of power for a transient? Can two amplifiers with similar SINAD and steady state power ratings differ significantly (due to their design) in how they respond to power demands? And if so, does the distortion profile change in some nonlinear way when one amplifier delivers a short peak of power vs another? Being a Magnepan owner I always hear I should use "high current" amplifiers ... but there doesn't seem to be a technical standard for how to determine this capability. And once again, could two amplifiers capable of the same peak current output have different distortion characteristics at that peak? That's a good question, one that could probably be answered by actually listening.  Assuming two amps both had SINAD specs that were below the audibility threshold and similar power ratings, one might sound noticeably more dynamic than the other. |
|
|
|
Post by marcl on Jun 22, 2023 21:40:05 GMT -5
The problem is this... Audio amplifiers are a bit too complicated to compare accurately using one or two simple measurements. Therefore, attempting to do so, or imagining that you have done so, is unlikely to produce accurate results. (And, if you place excessive confidence in the results, they may also lead you to inaccurate and misleading conclusions.) 1. Most folks in the industry agree that THD and S/N are the two most significant measurements. Therefore, arguably, if you were to only have a single measurement, SINAD wouldn't be that bad of a choice. However, there are a lot of other things you can measure, and not everyone agrees on how important many of the others are. 2. As with many other things, when it comes to audio measurements, there are thresholds of audibility and practical limits. For example, while the specific numbers are still debated, everyone I know agrees that there are limits of audibility for both THD and S/N. That means that there are limits below which they are inaudible... so there is no real benefit of improving them beyond those limits. For example, most people I know agree that , undermost circumstances, an amplifier with 5% THD will probably sound worse than one with 0.5% THD. But most people I know also agree that "nobody can possibly hear the difference between 0.05% THD and 0.005% THD". And, likewise, once the S/N of a system is significantly better than your source material, you really cannot get any practical improvement much beyond that. (And, if you hear a difference between two amplifiers, both of which have THD and S/N well beyond those limits, then it's probably for some OTHER reason.) 3. The upshot of all this is that we often do tend to hear differences between amplifiers. And we often hear those differences in amplifiers whose basic measurements "are good enough that they should sound equally perfect". Therefore, either we're imagining that difference, or it's being caused by something else that we didn't measure. However, considering how many things we didn't measure, and how complex human hearing really is, that last possibility isn't at all unlikely. BUT WE WILL NEVER KNOW THAT THEY SOUND DIFFERENT TO BEGIN WITH IF WE NEVER LISTEN TO THEM.Everyone likes simple answers... So everyone likes simple questions... But they just aren't always good enough to get the job done properly... As the famous quote usually attributed to Albert Einstein goes: “Everything should be made as simple as possible, but not simpler” Something that I wonder about and I don't ever hear discussed .... what about a given amplifier's ability to deliver power, to deliver current through the wire, with respect to time? What I mean by this is that amplifier measurements are done in some steady state condition. But what happens in very short instants when the source demands a lot of power for a transient? Can two amplifiers with similar SINAD and steady state power ratings differ significantly (due to their design) in how they respond to power demands? And if so, does the distortion profile change in some nonlinear way when one amplifier delivers a short peak of power vs another? Being a Magnepan owner I always hear I should use "high current" amplifiers ... but there doesn't seem to be a technical standard for how to determine this capability. And once again, could two amplifiers capable of the same peak current output have different distortion characteristics at that peak? If that's the case, there MUST be a way to measure that ... design for that ... make an amp that will predictably sound better for that reason. |
|
KeithL
Administrator 
Posts: 10,256
|
Post by KeithL on Jun 23, 2023 9:52:04 GMT -5
That is sort of an interesting subject... but also one that many people seem to not understand very well. The first thing to understand is that the amount of current required to drive a load is determined by the load. This means that, in order to play a certain bit of audio content, at a certain level, through a certain speaker, a certain amount of current will be required. And, as long as two amplifiers are both able to play that song, through that speaker, at that same level, without distorting, THEN THEY ARE SUPPLYING THE SAME AMOUNT OF CURRENT. It doesn't matter if one of those amplifiers is capable of supplying more current... because the speaker is drawing the same amount of current. (Just as, if you connect a 12V 10 watt bulb to a car battery, or to a battery of the same voltage the size of a semi-trailer, it will draw exactly the same current, and consume the same 10 watts of power.) So, for a given source, and a given load, either the amplifier is able to supply sufficient current or it isn't... If the amplifier IS able to supply sufficient current then the music will play undistorted... And, if the amplifier IS NOT able to supply sufficient current, then there will be distortion... SO, JUST TO BE CLEAR, THERE IS NO BENEFIT TO AN AMPLIFIER THAT IS "ABLE" TO DELIVER MORE CURRENT THAN IT WILL BE REQUIRED TO DELIVER.Now, there is a small sort-of-exception to this... Most loudspeakers actually have one or more drivers which operate "more of less like an electric motor"... And, in this situation, the driver will usually actually have a slightly lower impedance when it is at rest than when it is moving... Likewise, once the driver is moving, when the signal from the amplifier stops, the driver will continue to move due to momentum (stored energy). And, because a motor is also a generator, this motion will result in that driver generating an electrical signal (back EMF). When this occurs the amplifier that is driving the speaker is required to sink (absorb) that signal in order to control the motion of the speaker. This is the mechanism by which "damping factor" enables an amplifier to "control a speaker more tightly". However both of these factors are accounted for by simply saying that "a typical loudspeaker has a rather complex dynamic impedance". AND THE POINT REMAINS THAT...- If the amplifier is unable to supply or sink enough current to meet the requirements posed by the load of the speaker attached to it then the result will be distortion. - If there is NO distortion than the amplifier IS meeting that requirement - and there would be no benefit to having an amplifier "that could supply more if anyone ever asked it to". The problem with your assertion is that it's NOT simply a matter of "peak current" ... You've got things like reactive loads, and non-linear load variations, and non-linear dynamic reactive loads ... Speakers vary very widely... which makes it impossible to devise "a single standard model of a typical speaker load" ... And, likewise, while it's pretty simple to run tests using steady state sine waves, there are an infinite number of other possibilities to consider ... (So we design and test based on "relatively normal speakers" and accept that "there will always be some strange speakers that fall outside the normal range".) However, just to be clear, Magneplanars are NOT especially odd or an exceptionally difficult speaker to drive in terms of impedance... They are simply very inefficient... and have a relatively low impedance... and so require an amplifier that is capable of delivering a lot of power... Yes, some models do have an impedance that drops rather low, especially at very high frequencies... But most Magneplanars simply require a very powerful amplifier... But a lot of people also confuse Magneplanars with certain specific models of electrostatic speakers... (Which ARE difficult for most amplifiers to drive because they have an impedance that is very low, and almost purely reactive, at high frequencies.) Something that I wonder about and I don't ever hear discussed .... what about a given amplifier's ability to deliver power, to deliver current through the wire, with respect to time? What I mean by this is that amplifier measurements are done in some steady state condition. But what happens in very short instants when the source demands a lot of power for a transient? Can two amplifiers with similar SINAD and steady state power ratings differ significantly (due to their design) in how they respond to power demands? And if so, does the distortion profile change in some nonlinear way when one amplifier delivers a short peak of power vs another? Being a Magnepan owner I always hear I should use "high current" amplifiers ... but there doesn't seem to be a technical standard for how to determine this capability. And once again, could two amplifiers capable of the same peak current output have different distortion characteristics at that peak? If that's the case, there MUST be a way to measure that ... design for that ... make an amp that will predictably sound better for that reason. |
|
|
|
Post by marcl on Jun 23, 2023 10:02:13 GMT -5
That is sort of an interesting subject... but also one that many people seem to not understand very well. The first thing to understand is that the amount of current required to drive a load is determined by the load. This means that, in order to play a certain bit of audio content, at a certain level, through a certain speaker, a certain amount of current will be required. And, as long as two amplifiers are both able to play that song, through that speaker, at that same level, without distorting, THEN THEY ARE SUPPLYING THE SAME AMOUNT OF CURRENT. It doesn't matter if one of those amplifiers is capable of supplying more current... because the speaker is drawing the same amount of current. (Just as, if you connect a 12V 10 watt bulb to a car battery, or to a battery of the same voltage the size of a semi-trailer, it will draw exactly the same current, and consume the same 10 watts of power.) So, for a given source, and a given load, either the amplifier is able to supply sufficient current or it isn't... If the amplifier IS able to supply sufficient current then the music will play undistorted... And, if the amplifier IS NOT able to supply sufficient current, then there will be distortion... SO, JUST TO BE CLEAR, THERE IS NO BENEFIT TO AN AMPLIFIER THAT IS "ABLE" TO DELIVER MORE CURRENT THAN IT WILL BE REQUIRED TO DELIVER.Now, there is a small sort-of-exception to this... Most loudspeakers actually have one or more drivers which operate "more of less like an electric motor"... And, in this situation, the driver will usually actually have a slightly lower impedance when it is at rest than when it is moving... Likewise, once the driver is moving, when the signal from the amplifier stops, the driver will continue to move due to momentum (stored energy). And, because a motor is also a generator, this motion will result in that driver generating an electrical signal (back EMF). When this occurs the amplifier that is driving the speaker is required to sink (absorb) that signal in order to control the motion of the speaker. This is the mechanism by which "damping factor" enables an amplifier to "control a speaker more tightly". However both of these factors are accounted for by simply saying that "a typical loudspeaker has a rather complex dynamic impedance". AND THE POINT REMAINS THAT...- If the amplifier is unable to supply or sink enough current to meet the requirements posed by the load of the speaker attached to it then the result will be distortion. - If there is NO distortion than the amplifier IS meeting that requirement - and there would be no benefit to having an amplifier "that could supply more if anyone ever asked it to". The problem with your assertion is that it's NOT simply a matter of "peak current" ... You've got things like reactive loads, and non-linear load variations, and non-linear dynamic reactive loads ... Speakers vary very widely... which makes it impossible to devise "a single standard model of a typical speaker load" ... And, likewise, while it's pretty simple to run tests using steady state sine waves, there are an infinite number of other possibilities to consider ... (So we design and test based on "relatively normal speakers" and accept that "there will always be some strange speakers that fall outside the normal range".) However, just to be clear, Magneplanars are NOT especially odd or an exceptionally difficult speaker to drive in terms of impedance... They are simply very inefficient... and have a relatively low impedance... and so require an amplifier that is capable of delivering a lot of power... Yes, some models do have an impedance that drops rather low, especially at very high frequencies... But most Magneplanars simply require a very powerful amplifier... But a lot of people also confuse Magneplanars with certain specific models of electrostatic speakers... (Which ARE difficult for most amplifiers to drive because they have an impedance that is very low, and almost purely reactive, at high frequencies.) If that's the case, there MUST be a way to measure that ... design for that ... make an amp that will predictably sound better for that reason. That all makes sense (which is good, because I don't want to have to give back my EE degree  ) .... but I guess I should have been more specific in that I wonder - and lets use this essentially uniform resistive load of a Magnepan as the simplest example - can there be a difference in how quickly two amplifiers can respond to deliver the current. Not one able to deliver MORE than the other, but rather one being able to respond more quickly. And if there is a difference in how long it takes for the amp to reach the current output demanded by the load, could this result in audible effects? |
|
|
|
Post by mgbpuff on Jun 23, 2023 11:03:03 GMT -5
I guess that solves it - there's no reason for an amplifier to be any better than an Emotiva. Why am I not convinced? I think the difference is transient performance. Good transient duplication requires greater bandwidth and greater potential energy to make the moving mass of a speaker duplicate the original transient waveform. This requires overdesigned equipment. It requires much more force and speed capability than steady state alone would require (as much a 5 or 6 times). Do we need this for adequacy? Obviously, most of us can enjoy reproduced music with tamed down transients from the original; we do it all the time. But if its reality, the sense of being there in the live performance, that we are after, then really good transient performance has to be designed in.
|
|
|
|
Post by tchaik on Jun 23, 2023 12:48:37 GMT -5
That is sort of an interesting subject... but also one that many people seem to not understand very well. The first thing to understand is that the amount of current required to drive a load is determined by the load. This means that, in order to play a certain bit of audio content, at a certain level, through a certain speaker, a certain amount of current will be required. And, as long as two amplifiers are both able to play that song, through that speaker, at that same level, without distorting, THEN THEY ARE SUPPLYING THE SAME AMOUNT OF CURRENT. It doesn't matter if one of those amplifiers is capable of supplying more current... because the speaker is drawing the same amount of current. (Just as, if you connect a 12V 10 watt bulb to a car battery, or to a battery of the same voltage the size of a semi-trailer, it will draw exactly the same current, and consume the same 10 watts of power.) So, for a given source, and a given load, either the amplifier is able to supply sufficient current or it isn't... If the amplifier IS able to supply sufficient current then the music will play undistorted... And, if the amplifier IS NOT able to supply sufficient current, then there will be distortion... SO, JUST TO BE CLEAR, THERE IS NO BENEFIT TO AN AMPLIFIER THAT IS "ABLE" TO DELIVER MORE CURRENT THAN IT WILL BE REQUIRED TO DELIVER.Now, there is a small sort-of-exception to this... Most loudspeakers actually have one or more drivers which operate "more of less like an electric motor"... And, in this situation, the driver will usually actually have a slightly lower impedance when it is at rest than when it is moving... Likewise, once the driver is moving, when the signal from the amplifier stops, the driver will continue to move due to momentum (stored energy). And, because a motor is also a generator, this motion will result in that driver generating an electrical signal (back EMF). When this occurs the amplifier that is driving the speaker is required to sink (absorb) that signal in order to control the motion of the speaker. This is the mechanism by which "damping factor" enables an amplifier to "control a speaker more tightly". However both of these factors are accounted for by simply saying that "a typical loudspeaker has a rather complex dynamic impedance". AND THE POINT REMAINS THAT...- If the amplifier is unable to supply or sink enough current to meet the requirements posed by the load of the speaker attached to it then the result will be distortion. - If there is NO distortion than the amplifier IS meeting that requirement - and there would be no benefit to having an amplifier "that could supply more if anyone ever asked it to". The problem with your assertion is that it's NOT simply a matter of "peak current" ... You've got things like reactive loads, and non-linear load variations, and non-linear dynamic reactive loads ... Speakers vary very widely... which makes it impossible to devise "a single standard model of a typical speaker load" ... And, likewise, while it's pretty simple to run tests using steady state sine waves, there are an infinite number of other possibilities to consider ... (So we design and test based on "relatively normal speakers" and accept that "there will always be some strange speakers that fall outside the normal range".) However, just to be clear, Magneplanars are NOT especially odd or an exceptionally difficult speaker to drive in terms of impedance... They are simply very inefficient... and have a relatively low impedance... and so require an amplifier that is capable of delivering a lot of power... Yes, some models do have an impedance that drops rather low, especially at very high frequencies... But most Magneplanars simply require a very powerful amplifier... But a lot of people also confuse Magneplanars with certain specific models of electrostatic speakers... (Which ARE difficult for most amplifiers to drive because they have an impedance that is very low, and almost purely reactive, at high frequencies.) That all makes sense (which is good, because I don't want to have to give back my EE degree ) .... but I guess I should have been more specific in that I wonder - and lets use this essentially uniform resistive load of a Magnepan as the simplest example - can there be a difference in how quickly two amplifiers can respond to deliver the current. Not one able to deliver MORE than the other, but rather one being able to respond more quickly. And if there is a difference in how long it takes for the amp to reach the current output demanded by the load, could this result in audible effects? I recall decades ago, they used to talk about slew rate. I wonder if that is still a thing? |
|
|
|
Post by geebo on Jun 23, 2023 13:09:20 GMT -5
That all makes sense (which is good, because I don't want to have to give back my EE degree ) .... but I guess I should have been more specific in that I wonder - and lets use this essentially uniform resistive load of a Magnepan as the simplest example - can there be a difference in how quickly two amplifiers can respond to deliver the current. Not one able to deliver MORE than the other, but rather one being able to respond more quickly. And if there is a difference in how long it takes for the amp to reach the current output demanded by the load, could this result in audible effects? I recall decades ago, they used to talk about slew rate. I wonder if that is still a thing? And don't forget rise time. |
|
|
|
Post by mgbpuff on Jun 23, 2023 13:23:43 GMT -5
Slew rate refers to how fast an input signal rate of change can be followed in the output. Measured in delta volts/delta time. An amp may contain devices (transistors, etc) that have limitations in how fast they can rise in voltage from one level to another. So obviously this will affect the reproduction accuracy. They may not talk much about slew anymore, but it is a real physical attribute that will never go away. High slew rates and high bandwidth go hand in hand in creating what some call a fast amplifier. Fast amplifiers produce transient source signals better than slow amplifiers.
|
|
KeithL
Administrator
Posts: 10,256
|
Post by KeithL on Jun 23, 2023 14:08:28 GMT -5
Slew rate is still "a thing" when it comes to design... However what you need to understand is that slew rate is not, in and of itself, "something where more is automatically better"... What happens is that, if there is insufficient slew rate at certain points in a circuit, the result will be distortion... But, once you do have more than sufficient slew rate, there is no specific benefit to having a significantly higher slew rate. The important factor to note here is that "the minimum slew rate that you need" depends on the application. Therefore it's important to be well aware of the slew rate you need at a specific point in a circuit, and be sure that you have it, as well as a bit of margin for error, when you are designing that circuit. But, when you see something like an op-amp, which boasts a really high slew rate, they're really just assuring the designer that "they won't have to worry about exceeding its capabilities". And, while it does mean that part will work well in a wide variety of applications, it doesn't necessarily mean that it will work better in applications where a high slew rate isn't needed. In simplest terms, in electronics, slew rate refers to "how fast the voltage of a signal can vary over time". So, for example, if you look at a sine wave, the voltage is actually varying the most quickly at the zero crossing point (that's where it has the highest slope). And, the higher the frequency of your signal, and the higher the amplitude of your signal, the higher the slew rate you will need to reproduce it accurately. And, if you have insufficient slew rate, high level high frequency sine waves will end up looking like triangles, as the circuit becomes unable to reproduce them properly. And that difference between what they should look like, and what they do look like, which happens at the same spot on each waveform, is a form of THD. 1. This sort of distortion can be difficult to detect because, unlike clipping, it isn't obvious on an oscilloscope, especially with an irregular musical waveform. 2. Again, because music has such an irregular waveform, it may only happen occasionally. 3. This is not always a limitation of a part like an op amp; it can often result when a perfectly good part is used incorrectly, or beyond its design limits. (Back in the early days certain circuit designs commonly used in phono preamps were often designed in such a way that they had unexpectedly high levels of this type of distortion.) Another way in which slew rate comes up is in the overall slew rate of a section of circuitry... I'm going to oversimplify this a bit... but you'll get the idea... For a given section of circuitry, if you change the voltage at the input, it will take a finite amount of time for that change to show up at the output (this is the slew rate of that circuit.... ) But, when we apply negative feedback around a circuit, we do so by taking part of the output of the circuit, and applying it to the input. However, because the signal has been delayed on its way through that circuit, the output is delayed relative to the input, "so they don't exactly line up like we expect". And, if we calculate things like gain for an op amp, using the simplest sort of calculations, we are sort of assuming that they do line up perfectly. And, since they do not, that "discrepancy" imposes design limitations on the relationship between the gain, frequency response, and amount of feedback that can safely be used. (And, if we fail to understand those limitations, for example by applying too much gain, or too much feedback, in a circuit with an insufficient slew rate, then our circuit may malfunction in a variety of unpleasant ways.) The point here, and the answer to your question, is that slew rate is an important factor in the internal circuit design of an amplifier or preamp. And, if it isn't properly accounted for in the design, the result will be poor performance. But the slew rate that is necessary, sufficient, or even beneficial, is going to depend on many internal design details. And, unless you're designing the internal circuitry itself, the overall slew rate of a complete preamp or power amp, as "a specification to look for", really doesn't matter. That all makes sense (which is good, because I don't want to have to give back my EE degree ) .... but I guess I should have been more specific in that I wonder - and lets use this essentially uniform resistive load of a Magnepan as the simplest example - can there be a difference in how quickly two amplifiers can respond to deliver the current. Not one able to deliver MORE than the other, but rather one being able to respond more quickly. And if there is a difference in how long it takes for the amp to reach the current output demanded by the load, could this result in audible effects? I recall decades ago, they used to talk about slew rate. I wonder if that is still a thing? |
|
|
|
Post by mgbpuff on Jun 23, 2023 14:20:26 GMT -5
"For a given section of circuitry, if you change the voltage at the input, it will take a finite amount of time for that change to show up at the output (this is the slew rate of that circuit.... )" I recall decades ago, they used to talk about slew rate. I wonder if that is still a thing? Actually that is propagation delay not slew rate. |
|
KeithL
Administrator
Posts: 10,256
|
Post by KeithL on Jun 23, 2023 14:24:35 GMT -5
The short answer to your question is no... There is no mechanism in our amplifiers, or any other amplifier I know of, that would "ramp up its ability to deliver current over time". (In the sense that a generating station could put more generators online to cover peak demand.) The only limitation of that sort is going to involve the limitation of the frequency response of the output devices themselves... And that's going to be far above the entire audio frequency range... .................................. That all makes sense (which is good, because I don't want to have to give back my EE degree ) .... but I guess I should have been more specific in that I wonder - and lets use this essentially uniform resistive load of a Magnepan as the simplest example - can there be a difference in how quickly two amplifiers can respond to deliver the current. Not one able to deliver MORE than the other, but rather one being able to respond more quickly. And if there is a difference in how long it takes for the amp to reach the current output demanded by the load, could this result in audible effects? |
|
|
|
Post by tchaik on Jun 23, 2023 15:35:05 GMT -5
I recall decades ago, they used to talk about slew rate. I wonder if that is still a thing? And don't forget rise time. only if you are baking bread |
|
) .... but I guess I should have been more specific in that I wonder - and lets use this essentially uniform resistive load of a Magnepan as the simplest example - can there be a difference in how quickly two amplifiers can respond to deliver the current. Not one able to deliver MORE than the other, but rather one being able to respond more quickly. And if there is a difference in how long it takes for the amp to reach the current output demanded by the load, could this result in audible effects?
