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#1
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Clean Power?
When referring to amplifiers the favorite catch-phrase of audiophiles
seems to be "clean power". As an ignorant novice I would like to know what is meant by "clean power" and how do I achieve it. Also, I once heard something about voltage matching an amplifier with a head unit but if I set my amp to 4v (same as the preouts on my head unit) I can barely hear my subs. Do I need to add a bigger amp to get the benefit of voltage matching? Will this theoretically provide "cleaner power"? |
#2
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Clean Power?
I think 'clean power' would be more of a product of a high quality amp, not
so much from an install. In other words, an amp that amplifies the signal without a lot of distortion and extra crap. Zapco and Xtant are good examples of ultra clean amplifiers. "Dylan X" wrote in message m... When referring to amplifiers the favorite catch-phrase of audiophiles seems to be "clean power". As an ignorant novice I would like to know what is meant by "clean power" and how do I achieve it. Also, I once heard something about voltage matching an amplifier with a head unit but if I set my amp to 4v (same as the preouts on my head unit) I can barely hear my subs. Do I need to add a bigger amp to get the benefit of voltage matching? Will this theoretically provide "cleaner power"? |
#3
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Clean Power?
I think 'clean power' would be more of a product of a high quality amp,
not so much from an install. In other words, an amp that amplifies the signal without a lot of distortion and extra crap. Zapco and Xtant are good examples of ultra clean amplifiers. Doesn't matter who makes it. All amplifiers made these days have distortion byproducts well below audible threshold. Especially compared to the distortion that arises from driving your amp into clipping, which is surprisingly common. |
#4
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Clean Power?
"Mark Zarella" wrote in message ... I think 'clean power' would be more of a product of a high quality amp, not so much from an install. In other words, an amp that amplifies the signal without a lot of distortion and extra crap. Zapco and Xtant are good examples of ultra clean amplifiers. Doesn't matter who makes it. All amplifiers made these days have distortion byproducts well below audible threshold. Especially compared to the distortion that arises from driving your amp into clipping, which is surprisingly common. Eh maybe, but I refuse to believe that a Jensen or Dual amp is going to sound as good and clean as a Zapco or Xtant. |
#5
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Clean Power?
Doesn't matter who makes it. All amplifiers made these days have
distortion byproducts well below audible threshold. Especially compared to the distortion that arises from driving your amp into clipping, which is surprisingly common. Eh maybe, but I refuse to believe that a Jensen or Dual amp is going to sound as good and clean as a Zapco or Xtant. Why? Because the price tag says it does? |
#6
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Clean Power?
"Mark Zarella" wrote in message ... Doesn't matter who makes it. All amplifiers made these days have distortion byproducts well below audible threshold. Especially compared to the distortion that arises from driving your amp into clipping, which is surprisingly common. Eh maybe, but I refuse to believe that a Jensen or Dual amp is going to sound as good and clean as a Zapco or Xtant. Why? Because the price tag says it does? No, mainly becuase of the design and manufacturing. The power supply section in a Zapco amp alone costs more than all the parts in some crap amp. |
#7
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Clean Power?
When referring to amplifiers the favorite catch-phrase of audiophiles
seems to be "clean power". As an ignorant novice I would like to know what is meant by "clean power" and how do I achieve it. There's no such thing. Power is power. What's usually meant is low distortion and noise. It's easily attainable simply by not driving your amp into clipping. That means use sufficient amplification for your needs. Also, I once heard something about voltage matching an amplifier with a head unit but if I set my amp to 4v (same as the preouts on my head unit) I can barely hear my subs. Do I need to add a bigger amp to get the benefit of voltage matching? Will this theoretically provide "cleaner power"? No. NEVER match your amplifier's gain setting to the nominal rating on your head unit. It doesn't work because a) the output voltage of the HU doesn't always meet the nominal rating, especially when listening to quieter passages; b) filtering out higher frequencies with the LPF reduces voltage. Go strictly by ear when setting gains. There's a tutorial at installer.com's tech pages. |
#8
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Clean Power?
Let me shed some light:
There is such a thing as "clean" and "dirty" power. A perfect case in point would be to run your amplifier with a cheap battery charger as its B+ supply. You will hear a tremendous amount of "hum". In other words, it is "dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 ) of automotive batteries in series. Tap the "GND" from the connection between battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the the top and bottom posts. to do this, you must eliminate the SMPS section and some other items. The Rectifying diodes and the bulk rail capacitors to be exact. You now have "clean" Power for your 400W/ch RMS amplifier. Many things can affect just how "clean" an amplfier is. Power supply topology, filter capacitors, Inductors, ferrite beads, transformer type, board layout, star grounding, trace capacitance, trace inductance, PCB layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a "clean" power amplifier. Do any one or all these things wrong and you now have a "dirty" power amplifier. There is even an extreme case where when the output rails do not have enough bulk capacitance, the output feedback circuit goes "open loop" for just a microsecond or so. In this time, the output transistors modulate or "burst" at their peaks causing audible distortion. Lots of cheap amplifiers will do this just before clipping at full power. Not all things are created equal. Power is one of them. If you want a mechanical analog, how about a V-8 piston engine and a jet turbine John Andreen Mark Zarella wrote: When referring to amplifiers the favorite catch-phrase of audiophiles seems to be "clean power". As an ignorant novice I would like to know what is meant by "clean power" and how do I achieve it. There's no such thing. Power is power. What's usually meant is low distortion and noise. It's easily attainable simply by not driving your amp into clipping. That means use sufficient amplification for your needs. Also, I once heard something about voltage matching an amplifier with a head unit but if I set my amp to 4v (same as the preouts on my head unit) I can barely hear my subs. Do I need to add a bigger amp to get the benefit of voltage matching? Will this theoretically provide "cleaner power"? No. NEVER match your amplifier's gain setting to the nominal rating on your head unit. It doesn't work because a) the output voltage of the HU doesn't always meet the nominal rating, especially when listening to quieter passages; b) filtering out higher frequencies with the LPF reduces voltage. Go strictly by ear when setting gains. There's a tutorial at installer.com's tech pages. |
#9
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Clean Power?
There is such a thing as "clean" and "dirty" power. A perfect case in
point would be to run your amplifier with a cheap battery charger as its B+ supply. You will hear a tremendous amount of "hum". In other words, it is "dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 ) of automotive batteries in series. Tap the "GND" from the connection between battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the the top and bottom posts. to do this, you must eliminate the SMPS section and some other items. The Rectifying diodes and the bulk rail capacitors to be exact. You now have "clean" Power for your 400W/ch RMS amplifier. Many things can affect just how "clean" an amplfier is. Power supply topology, filter capacitors, Inductors, ferrite beads, transformer type, board layout, star grounding, trace capacitance, trace inductance, PCB layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a "clean" power amplifier. Do any one or all these things wrong and you now have a "dirty" power amplifier. There is even an extreme case where when the output rails do not have enough bulk capacitance, the output feedback circuit goes "open loop" for just a microsecond or so. In this time, the output transistors modulate or "burst" at their peaks causing audible distortion. Lots of cheap amplifiers will do this just before clipping at full power. Not all things are created equal. Power is one of them. If you want a mechanical analog, how about a V-8 piston engine and a jet turbine That's all well and good, but the important thing to examine here is whether the results are significant during normal operation. Hint: by significant, I mean audible. While there are several ways to lower distortion (sometimes at the expense of noise, or at the expense of reliability, or at the expense of other forms of distortion, and so forth), there is of course a threshold at which further reduction is not warranted, nor is it necessarily recommended since there's almost always a tradeoff in some manner or another. So your engine analog holds true, but if your application is to just drive down a road, then either one will perform as well as the other. |
#10
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Clean Power?
"Mark Zarella" wrote in message ... So your engine analog holds true, but if your application is to just drive down a road, then either one will perform as well as the other. I guess that means that you run the cheapest amps you could find, correct? By your logic a Rockwood sounds exactly like a McIntosh and it costs $2000 less, so do you run Rockwood amps? Dual? Pyramid? |
#11
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Clean Power?
So your engine analog holds true, but if your application is to just
drive down a road, then either one will perform as well as the other. I guess that means that you run the cheapest amps you could find, correct? Assuming they delivered the power you're after and that they had the features and reliability you're looking for, then yeah, price is generally the next consideration. By your logic a Rockwood sounds exactly like a McIntosh and it costs $2000 less, so do you run Rockwood amps? Dual? Pyramid? I'd run a Pyramid before I'd run a McIntosh, as long as the Pyramid was powerful enough and had the features I wanted. But, since neither manufacturer makes one with the features I want, I personally wouldn't own either. |
#12
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Clean Power?
Mr Zarella
You are correct, there is always a trade-off between a "clean" amplifier and a "dirty" amplifier. But the "dirty" amplifier will always loose in terms of reliability, distortion, sound quality etc. All at the expense of good Engineering practices and a handful of parts. On a side note, what would you rather be driving, a Yugo or a Mercedes? Ok, not the same, but how about a Yugo or a Ford Focus? But if your life depended on its proper operation all the time, which would you choose? Here is another case in point. Old school PPI amplifiers. Some of these amplifiers are over 15 years old and they are still operating and making great sound. In fact, these units are still highly sought after. Can you say the same for an equally aged Pioneer or Sony? I think you are perhaps using a shifting baseline as to what is "clean" today. Could you also be confusing distortion with noise? They are not the same. You should do some investigation on these subjects. What you say is a measurement of distortion is actually called "THD +N" a.k.a. Total Harmonic Distortion + Noise. Then to make matters worse, some audio companies use filters (read A-weighted) to make there units appear to have low THD+N. To add even more confusion into the mix, this "THD+N" is almost always computationally measured using FFT methods. There are more than a dozen FFT windows ( read measuring envelope ) that can be used to make the measurement. Each will give a return a different value for "THD+N". There is one more thing about measuring "THD+N". One must also specify the power of the signal being measured. One can measure at 1W, 5W, Full rated power, etc. "THD+N" is not constant at all power levels. It is usually higher at very low power levels and very high power levels. At very low power levels, the major component comes from "noise". At very high power levels, the major component comes from "THD". Really "clean" amplifiers have "TH +N" values nearly equal at all power levels under clipping. I can take even the "dirtiest" amplifier and measure extremely low values of distortion. On the order of 1/1000 of a %. That is, if I can choose my own method and power level of distortion measurement. There is also harmonic distortion caused by the sum and difference of two signals. Let's say a 40 kHz square wave from a power supply and a 1 kHz sine wave. There will be strong harmonic distortion at 39 kHz and 41 kHz. There are also artifacts called sub-harmonics of these two signals that will be present. These are the artifacts that can appear down in the audio spectrum. I would also like to point out that music isn't just 1 kHz, but a plethora of frequencies. I have told this group many times not to be concerned with "THD+N" as a figure of merit when buying an amplifier. The human ear doesn't mind even 1-3% THD. It is a "Marketing Tool" designed to sway the masses. Go listen to a high quality pure tube amplifier and a high quality transistorized amplifier of the same output power specifications. Do this test blindly. I am absolutely certain that you will always pick the tube amplifier over the transistorized one as having the better sound. But, that tube amplifier will have distortion figures SEVERAL HUNDRED TIMES WORSE than the transistorized amplifier. Instead, try to buy an amplifier that has Low "TIM" and low S/N. TIM stands for Transient Intermodulation Distortion. Good audio distortion analyzers can find this kind of distortion using the "IMD" settings. Now, onto the subject of noise. Noise is ever present in the audio world. It comes from the amplifiers SMPS. It comes from the Automobiles charging system. It comes from solar wind. It comes from the power transmission lines. In short, it comes from just about everywhere. In my last post, I stated several things that make for a "clean" amplifier. Those things are the items or methodologies used to eliminate or diminish the ingress of noise into an amplifier. I forgot one them. Decoupling capacitors. Once again, do not do any or all of those items, and more effective noise will make it into the audio path. Do all of them right and you will diminish the ingress of noise into the audio path and have a "clean" amplifier. I have measured and tested amplifiers from many of the "top" car audio companies. Some had signal to noise ratios of -50dB, some had signal to noise ratios greater than -100dB. In other words, the best amplifiers S/N was 64 times better than the worst. The reason, one amplifier was more "clean" than anothers. Once again, you can fudge these numbers too. S/N is different depending upon the position of the gain pot. At max gain, S/N to noise will be different than min gain. The difference, a handful of parts and good Engineering practices. QED John Andreen Mark Zarella wrote: There is such a thing as "clean" and "dirty" power. A perfect case in point would be to run your amplifier with a cheap battery charger as its B+ supply. You will hear a tremendous amount of "hum". In other words, it is "dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 ) of automotive batteries in series. Tap the "GND" from the connection between battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the the top and bottom posts. to do this, you must eliminate the SMPS section and some other items. The Rectifying diodes and the bulk rail capacitors to be exact. You now have "clean" Power for your 400W/ch RMS amplifier. Many things can affect just how "clean" an amplfier is. Power supply topology, filter capacitors, Inductors, ferrite beads, transformer type, board layout, star grounding, trace capacitance, trace inductance, PCB layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a "clean" power amplifier. Do any one or all these things wrong and you now have a "dirty" power amplifier. There is even an extreme case where when the output rails do not have enough bulk capacitance, the output feedback circuit goes "open loop" for just a microsecond or so. In this time, the output transistors modulate or "burst" at their peaks causing audible distortion. Lots of cheap amplifiers will do this just before clipping at full power. Not all things are created equal. Power is one of them. If you want a mechanical analog, how about a V-8 piston engine and a jet turbine That's all well and good, but the important thing to examine here is whether the results are significant during normal operation. Hint: by significant, I mean audible. While there are several ways to lower distortion (sometimes at the expense of noise, or at the expense of reliability, or at the expense of other forms of distortion, and so forth), there is of course a threshold at which further reduction is not warranted, nor is it necessarily recommended since there's almost always a tradeoff in some manner or another. So your engine analog holds true, but if your application is to just drive down a road, then either one will perform as well as the other. |
#13
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Clean Power?
John Andreen. The only SANE person (besides myself) that I've seen in this
newsgroup yet. You guys spouting out advice and acting like you know everything should listen to Mr. Andreen. Trust me, you'll learn something. "John Andreen" wrote in message news:tMXJb.26126$i55.5289@fed1read06... Mr Zarella You are correct, there is always a trade-off between a "clean" amplifier and a "dirty" amplifier. But the "dirty" amplifier will always loose in terms of reliability, distortion, sound quality etc. All at the expense of good Engineering practices and a handful of parts. On a side note, what would you rather be driving, a Yugo or a Mercedes? Ok, not the same, but how about a Yugo or a Ford Focus? But if your life depended on its proper operation all the time, which would you choose? Here is another case in point. Old school PPI amplifiers. Some of these amplifiers are over 15 years old and they are still operating and making great sound. In fact, these units are still highly sought after. Can you say the same for an equally aged Pioneer or Sony? I think you are perhaps using a shifting baseline as to what is "clean" today. Could you also be confusing distortion with noise? They are not the same. You should do some investigation on these subjects. What you say is a measurement of distortion is actually called "THD +N" a.k.a. Total Harmonic Distortion + Noise. Then to make matters worse, some audio companies use filters (read A-weighted) to make there units appear to have low THD+N. To add even more confusion into the mix, this "THD+N" is almost always computationally measured using FFT methods. There are more than a dozen FFT windows ( read measuring envelope ) that can be used to make the measurement. Each will give a return a different value for "THD+N". There is one more thing about measuring "THD+N". One must also specify the power of the signal being measured. One can measure at 1W, 5W, Full rated power, etc. "THD+N" is not constant at all power levels. It is usually higher at very low power levels and very high power levels. At very low power levels, the major component comes from "noise". At very high power levels, the major component comes from "THD". Really "clean" amplifiers have "TH +N" values nearly equal at all power levels under clipping. I can take even the "dirtiest" amplifier and measure extremely low values of distortion. On the order of 1/1000 of a %. That is, if I can choose my own method and power level of distortion measurement. There is also harmonic distortion caused by the sum and difference of two signals. Let's say a 40 kHz square wave from a power supply and a 1 kHz sine wave. There will be strong harmonic distortion at 39 kHz and 41 kHz. There are also artifacts called sub-harmonics of these two signals that will be present. These are the artifacts that can appear down in the audio spectrum. I would also like to point out that music isn't just 1 kHz, but a plethora of frequencies. I have told this group many times not to be concerned with "THD+N" as a figure of merit when buying an amplifier. The human ear doesn't mind even 1-3% THD. It is a "Marketing Tool" designed to sway the masses. Go listen to a high quality pure tube amplifier and a high quality transistorized amplifier of the same output power specifications. Do this test blindly. I am absolutely certain that you will always pick the tube amplifier over the transistorized one as having the better sound. But, that tube amplifier will have distortion figures SEVERAL HUNDRED TIMES WORSE than the transistorized amplifier. Instead, try to buy an amplifier that has Low "TIM" and low S/N. TIM stands for Transient Intermodulation Distortion. Good audio distortion analyzers can find this kind of distortion using the "IMD" settings. Now, onto the subject of noise. Noise is ever present in the audio world. It comes from the amplifiers SMPS. It comes from the Automobiles charging system. It comes from solar wind. It comes from the power transmission lines. In short, it comes from just about everywhere. In my last post, I stated several things that make for a "clean" amplifier. Those things are the items or methodologies used to eliminate or diminish the ingress of noise into an amplifier. I forgot one them. Decoupling capacitors. Once again, do not do any or all of those items, and more effective noise will make it into the audio path. Do all of them right and you will diminish the ingress of noise into the audio path and have a "clean" amplifier. I have measured and tested amplifiers from many of the "top" car audio companies. Some had signal to noise ratios of -50dB, some had signal to noise ratios greater than -100dB. In other words, the best amplifiers S/N was 64 times better than the worst. The reason, one amplifier was more "clean" than anothers. Once again, you can fudge these numbers too. S/N is different depending upon the position of the gain pot. At max gain, S/N to noise will be different than min gain. The difference, a handful of parts and good Engineering practices. QED John Andreen Mark Zarella wrote: There is such a thing as "clean" and "dirty" power. A perfect case in point would be to run your amplifier with a cheap battery charger as its B+ supply. You will hear a tremendous amount of "hum". In other words, it is "dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 ) of automotive batteries in series. Tap the "GND" from the connection between battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the the top and bottom posts. to do this, you must eliminate the SMPS section and some other items. The Rectifying diodes and the bulk rail capacitors to be exact. You now have "clean" Power for your 400W/ch RMS amplifier. Many things can affect just how "clean" an amplfier is. Power supply topology, filter capacitors, Inductors, ferrite beads, transformer type, board layout, star grounding, trace capacitance, trace inductance, PCB layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a "clean" power amplifier. Do any one or all these things wrong and you now have a "dirty" power amplifier. There is even an extreme case where when the output rails do not have enough bulk capacitance, the output feedback circuit goes "open loop" for just a microsecond or so. In this time, the output transistors modulate or "burst" at their peaks causing audible distortion. Lots of cheap amplifiers will do this just before clipping at full power. Not all things are created equal. Power is one of them. If you want a mechanical analog, how about a V-8 piston engine and a jet turbine That's all well and good, but the important thing to examine here is whether the results are significant during normal operation. Hint: by significant, I mean audible. While there are several ways to lower distortion (sometimes at the expense of noise, or at the expense of reliability, or at the expense of other forms of distortion, and so forth), there is of course a threshold at which further reduction is not warranted, nor is it necessarily recommended since there's almost always a tradeoff in some manner or another. So your engine analog holds true, but if your application is to just drive down a road, then either one will perform as well as the other. |
#14
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Clean Power?
On Sun, 04 Jan 2004 10:12:23 -0700, John Andreen
wrote: Mr Zarella You are correct, there is always a trade-off between a "clean" amplifier and a "dirty" amplifier. But the "dirty" amplifier will always loose in terms of reliability, distortion, sound quality etc. All at the expense of good Engineering practices and a handful of parts. On a side note, what would you rather be driving, a Yugo or a Mercedes? Ok, not the same, but how about a Yugo or a Ford Focus? But if your life depended on its proper operation all the time, which would you choose? Here is another case in point. Old school PPI amplifiers. Some of these amplifiers are over 15 years old and they are still operating and making great sound. In fact, these units are still highly sought after. Can you say the same for an equally aged Pioneer or Sony? I think you are perhaps using a shifting baseline as to what is "clean" today. http://silverpioneer.com/ Could you also be confusing distortion with noise? They are not the same. You should do some investigation on these subjects. What you say is a measurement of distortion is actually called "THD +N" a.k.a. Total Harmonic Distortion + Noise. Then to make matters worse, some audio companies use filters (read A-weighted) to make there units appear to have low THD+N. To add even more confusion into the mix, this "THD+N" is almost always computationally measured using FFT methods. There are more than a dozen FFT windows ( read measuring envelope ) that can be used to make the measurement. Each will give a return a different value for "THD+N". There is one more thing about measuring "THD+N". One must also specify the power of the signal being measured. One can measure at 1W, 5W, Full rated power, etc. "THD+N" is not constant at all power levels. It is usually higher at very low power levels and very high power levels. At very low power levels, the major component comes from "noise". At very high power levels, the major component comes from "THD". Really "clean" amplifiers have "TH +N" values nearly equal at all power levels under clipping. I can take even the "dirtiest" amplifier and measure extremely low values of distortion. On the order of 1/1000 of a %. That is, if I can choose my own method and power level of distortion measurement. There is also harmonic distortion caused by the sum and difference of two signals. Let's say a 40 kHz square wave from a power supply and a 1 kHz sine wave. There will be strong harmonic distortion at 39 kHz and 41 kHz. There are also artifacts called sub-harmonics of these two signals that will be present. These are the artifacts that can appear down in the audio spectrum. I would also like to point out that music isn't just 1 kHz, but a plethora of frequencies. I have told this group many times not to be concerned with "THD+N" as a figure of merit when buying an amplifier. The human ear doesn't mind even 1-3% THD. It is a "Marketing Tool" designed to sway the masses. Go listen to a high quality pure tube amplifier and a high quality transistorized amplifier of the same output power specifications. Do this test blindly. I am absolutely certain that you will always pick the tube amplifier over the transistorized one as having the better sound. But, that tube amplifier will have distortion figures SEVERAL HUNDRED TIMES WORSE than the transistorized amplifier. Instead, try to buy an amplifier that has Low "TIM" and low S/N. TIM stands for Transient Intermodulation Distortion. Good audio distortion analyzers can find this kind of distortion using the "IMD" settings. Now, onto the subject of noise. Noise is ever present in the audio world. It comes from the amplifiers SMPS. It comes from the Automobiles charging system. It comes from solar wind. It comes from the power transmission lines. In short, it comes from just about everywhere. In my last post, I stated several things that make for a "clean" amplifier. Those things are the items or methodologies used to eliminate or diminish the ingress of noise into an amplifier. I forgot one them. Decoupling capacitors. Once again, do not do any or all of those items, and more effective noise will make it into the audio path. Do all of them right and you will diminish the ingress of noise into the audio path and have a "clean" amplifier. I have measured and tested amplifiers from many of the "top" car audio companies. Some had signal to noise ratios of -50dB, some had signal to noise ratios greater than -100dB. In other words, the best amplifiers S/N was 64 times better than the worst. The reason, one amplifier was more "clean" than anothers. Once again, you can fudge these numbers too. S/N is different depending upon the position of the gain pot. At max gain, S/N to noise will be different than min gain. The difference, a handful of parts and good Engineering practices. QED John Andreen Mark Zarella wrote: There is such a thing as "clean" and "dirty" power. A perfect case in point would be to run your amplifier with a cheap battery charger as its B+ supply. You will hear a tremendous amount of "hum". In other words, it is "dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 ) of automotive batteries in series. Tap the "GND" from the connection between battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the the top and bottom posts. to do this, you must eliminate the SMPS section and some other items. The Rectifying diodes and the bulk rail capacitors to be exact. You now have "clean" Power for your 400W/ch RMS amplifier. Many things can affect just how "clean" an amplfier is. Power supply topology, filter capacitors, Inductors, ferrite beads, transformer type, board layout, star grounding, trace capacitance, trace inductance, PCB layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a "clean" power amplifier. Do any one or all these things wrong and you now have a "dirty" power amplifier. There is even an extreme case where when the output rails do not have enough bulk capacitance, the output feedback circuit goes "open loop" for just a microsecond or so. In this time, the output transistors modulate or "burst" at their peaks causing audible distortion. Lots of cheap amplifiers will do this just before clipping at full power. Not all things are created equal. Power is one of them. If you want a mechanical analog, how about a V-8 piston engine and a jet turbine That's all well and good, but the important thing to examine here is whether the results are significant during normal operation. Hint: by significant, I mean audible. While there are several ways to lower distortion (sometimes at the expense of noise, or at the expense of reliability, or at the expense of other forms of distortion, and so forth), there is of course a threshold at which further reduction is not warranted, nor is it necessarily recommended since there's almost always a tradeoff in some manner or another. So your engine analog holds true, but if your application is to just drive down a road, then either one will perform as well as the other. |
#15
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Clean Power?
Mr Zarella
You are correct, there is always a trade-off between a "clean" amplifier and a "dirty" amplifier. But the "dirty" amplifier will always loose in terms of reliability, distortion, sound quality etc. All at the expense of good Engineering practices and a handful of parts. I have to disagree with you on this point. But I suppose much of it depends on what you're referring to exactly when you use the term "dirty". I assume you're talking about distortion and noise, and maybe frequency response. Much of the distortion characteristics of an audio amplifier are due to the input stage circuitry, even moreso than the components. You can further reduce harmonic distortion trhough additional circuitry, however statistical reliability is sacrificed by doing so. PSRR methods are usually sufficient in even the simplest IPS designs, and noise is rarely an issue. The biggest issue to tackle is linearity when compensating for freq response imperfections. But I don't know of any modern-day class AB amplifiers that don't perform adequately in this respect. On a side note, what would you rather be driving, a Yugo or a Mercedes? Ok, not the same, but how about a Yugo or a Ford Focus? But if your life depended on its proper operation all the time, which would you choose? You're talking about reliability concerns I think, which I haven't disagreed with anyone on in this thread. The analogy when applied to sound quality does not apply, unless of course you're talking about driving 5 MPH down the road, in which case you wouldn't notice a difference. The reason I modify your analogy is because it completely neglects the measuring device: that is, the human brain. Here is another case in point. Old school PPI amplifiers. Some of these amplifiers are over 15 years old and they are still operating and making great sound. In fact, these units are still highly sought after. Can you say the same for an equally aged Pioneer or Sony? I think you are perhaps using a shifting baseline as to what is "clean" today. Not sure what reliability has to do with "clean"/"dirty". Could you also be confusing distortion with noise? They are not the same. You should do some investigation on these subjects. What you say is a measurement of distortion is actually called "THD +N" a.k.a. Total Harmonic Distortion + Noise. There are several sources of distortion (but the resulting types of distortion can most easily be narrowed down to harmonic distortion, intermodulation distortion, and phase distortion), and I don't believe I've narrowed it down to any of them. I've generally been referring to distortion, noise, frequency/phase response as a whole in the discussion of sound quality. Then to make matters worse, some audio companies use filters (read A-weighted) to make there units appear to have low THD+N Are you referring to the amplifier designs or the testing methodologies? To add even more confusion into the mix, this "THD+N" is almost always computationally measured using FFT methods. There are more than a dozen FFT windows ( read measuring envelope ) that can be used to make the measurement. Each will give a return a different value for "THD+N". The estimation procedure is not vital in this case. A confidence interval can be derived from any estimation procedure, and if the sample size is large enough (and given the limited bandwidth in audio) it's quite easy to limit the bias and variance to negligible levels, especially with proper windowing when applicable. There is one more thing about measuring "THD+N". One must also specify the power of the signal being measured. One can measure at 1W, 5W, Full rated power, etc. "THD+N" is not constant at all power levels. It is usually higher at very low power levels and very high power levels. At very low power levels, the major component comes from "noise". At very high power levels, the major component comes from "THD". Really "clean" amplifiers have "TH +N" values nearly equal at all power levels under clipping. Right. Distortion levels vary significantly with different power levels. Good distortion measurements (like the kind I use ) take this into account by performing the analysis at different power levels and with different signals. Harmonic distortion is easy. It's IMD where you start having to make seemingly arbitrary (though not necessarily incomplete) decisions. I can take even the "dirtiest" amplifier and measure extremely low values of distortion. On the order of 1/1000 of a %. That is, if I can choose my own method and power level of distortion measurement. That's why it's important to use representative techniques and keep them uniform. There is also harmonic distortion caused by the sum and difference of two signals. Let's say a 40 kHz square wave from a power supply and a 1 kHz sine wave. There will be strong harmonic distortion at 39 kHz and 41 kHz. There are also artifacts called sub-harmonics of these two signals that will be present. These are the artifacts that can appear down in the audio spectrum. I would also like to point out that music isn't just 1 kHz, but a plethora of frequencies. I have told this group many times not to be concerned with "THD+N" as a figure of merit when buying an amplifier. The human ear doesn't mind even 1-3% THD. Well, that can depend on a number of other factors, but your point is well taken. It is a "Marketing Tool" designed to sway the masses. Go listen to a high quality pure tube amplifier and a high quality transistorized amplifier of the same output power specifications. Do this test blindly. I am absolutely certain that you will always pick the tube amplifier over the transistorized one as having the better sound. But, that tube amplifier will have distortion figures SEVERAL HUNDRED TIMES WORSE than the transistorized amplifier. Instead, try to buy an amplifier that has Low "TIM" and low S/N. TIM stands for Transient Intermodulation Distortion. Good audio distortion analyzers can find this kind of distortion using the "IMD" settings. I agree completely. But note that the discussion at hand is picking apart the difference, rather than the more "pleasing" sound. Several reports have demonstrated that many listeners actually prefer even order harmonics, which tend to be especially high in tube designs. However, other reports say quite the opposite, and asymmetrical clipping which often results in high even order harmonic content is generally viewed as unfavorable. The most telling paper I've read on the subject is Farrimond, Perceptual and Motor Skills,1990,70. He found that in the subjective evaluation of audio components, it was quite easy to implement paradigms where the users could tell the difference between two sounds but could not reliably label which was more or less distorted. Now, onto the subject of noise. Noise is ever present in the audio world. It comes from the amplifiers SMPS. It comes from the Automobiles charging system. It comes from solar wind. It comes from the power transmission lines. In short, it comes from just about everywhere. In my last post, I stated several things that make for a "clean" amplifier. Those things are the items or methodologies used to eliminate or diminish the ingress of noise into an amplifier. I forgot one them. Decoupling capacitors. Once again, do not do any or all of those items, and more effective noise will make it into the audio path. Do all of them right and you will diminish the ingress of noise into the audio path and have a "clean" amplifier. I don't know of any modern amplifiers where the inherent noise is a problem. In fact, the noise resulting from less-than-stellar installation tends to be much larger than that which cannot be overcome in the amplifier. I said earlier in the thread however that some amplifiers are more prone to noise than others, but the significant portion can be eliminated with good installation techniques. It wasn't too long ago that -70dB to -80dB was considered good. And IMO, in the car that still is perfectly sufficient. Now people quibble over the difference between -100dB and -92dB. Again, it's inconsequential. I have measured and tested amplifiers from many of the "top" car audio companies. Some had signal to noise ratios of -50dB, some had signal to noise ratios greater than -100dB. In other words, the best amplifiers S/N was 64 times better than the worst. The reason, one amplifier was more "clean" than anothers. Once again, you can fudge these numbers too. S/N is different depending upon the position of the gain pot. At max gain, S/N to noise will be different than min gain. The difference, a handful of parts and good Engineering practices. QED Our disagreement isn't in the electrical aspect of the amplifier. We agree on just about all of it. Rather, it's the psychophysical end of things. Pushing distortion down past the noise floor is unnecessary. Trying to obtain -100dB noise levels is unnecessary. Trying to minimize freq response dips to below 1dB is unnecessary. This can all be demonstrated in psychophysical experiments. And these so-called "dirty amplifiers" (even when, in many cases, the cheaper amplifier is actually "cleaner" than the more expensive one), do not exhibit deficiencies in any of these categories that can be detected by us listeners, especially in an electric and acoustic noise box like a car. |
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Clean Power?
You could say the same about an original Sony XES-M1 or M3... I think
you need to establish an apples to apples comparison, can't compare premium product with run of the mill stuff and expect them to "age" the same. JD John Andreen wrote: Mr Zarella You are correct, there is always a trade-off between a "clean" amplifier and a "dirty" amplifier. But the "dirty" amplifier will always loose in terms of reliability, distortion, sound quality etc. All at the expense of good Engineering practices and a handful of parts. On a side note, what would you rather be driving, a Yugo or a Mercedes? Ok, not the same, but how about a Yugo or a Ford Focus? But if your life depended on its proper operation all the time, which would you choose? Here is another case in point. Old school PPI amplifiers. Some of these amplifiers are over 15 years old and they are still operating and making great sound. In fact, these units are still highly sought after. Can you say the same for an equally aged Pioneer or Sony? I think you are perhaps using a shifting baseline as to what is "clean" today. Could you also be confusing distortion with noise? They are not the same. You should do some investigation on these subjects. What you say is a measurement of distortion is actually called "THD +N" a.k.a. Total Harmonic Distortion + Noise. Then to make matters worse, some audio companies use filters (read A-weighted) to make there units appear to have low THD+N. To add even more confusion into the mix, this "THD+N" is almost always computationally measured using FFT methods. There are more than a dozen FFT windows ( read measuring envelope ) that can be used to make the measurement. Each will give a return a different value for "THD+N". There is one more thing about measuring "THD+N". One must also specify the power of the signal being measured. One can measure at 1W, 5W, Full rated power, etc. "THD+N" is not constant at all power levels. It is usually higher at very low power levels and very high power levels. At very low power levels, the major component comes from "noise". At very high power levels, the major component comes from "THD". Really "clean" amplifiers have "TH +N" values nearly equal at all power levels under clipping. I can take even the "dirtiest" amplifier and measure extremely low values of distortion. On the order of 1/1000 of a %. That is, if I can choose my own method and power level of distortion measurement. There is also harmonic distortion caused by the sum and difference of two signals. Let's say a 40 kHz square wave from a power supply and a 1 kHz sine wave. There will be strong harmonic distortion at 39 kHz and 41 kHz. There are also artifacts called sub-harmonics of these two signals that will be present. These are the artifacts that can appear down in the audio spectrum. I would also like to point out that music isn't just 1 kHz, but a plethora of frequencies. I have told this group many times not to be concerned with "THD+N" as a figure of merit when buying an amplifier. The human ear doesn't mind even 1-3% THD. It is a "Marketing Tool" designed to sway the masses. Go listen to a high quality pure tube amplifier and a high quality transistorized amplifier of the same output power specifications. Do this test blindly. I am absolutely certain that you will always pick the tube amplifier over the transistorized one as having the better sound. But, that tube amplifier will have distortion figures SEVERAL HUNDRED TIMES WORSE than the transistorized amplifier. Instead, try to buy an amplifier that has Low "TIM" and low S/N. TIM stands for Transient Intermodulation Distortion. Good audio distortion analyzers can find this kind of distortion using the "IMD" settings. Now, onto the subject of noise. Noise is ever present in the audio world. It comes from the amplifiers SMPS. It comes from the Automobiles charging system. It comes from solar wind. It comes from the power transmission lines. In short, it comes from just about everywhere. In my last post, I stated several things that make for a "clean" amplifier. Those things are the items or methodologies used to eliminate or diminish the ingress of noise into an amplifier. I forgot one them. Decoupling capacitors. Once again, do not do any or all of those items, and more effective noise will make it into the audio path. Do all of them right and you will diminish the ingress of noise into the audio path and have a "clean" amplifier. I have measured and tested amplifiers from many of the "top" car audio companies. Some had signal to noise ratios of -50dB, some had signal to noise ratios greater than -100dB. In other words, the best amplifiers S/N was 64 times better than the worst. The reason, one amplifier was more "clean" than anothers. Once again, you can fudge these numbers too. S/N is different depending upon the position of the gain pot. At max gain, S/N to noise will be different than min gain. The difference, a handful of parts and good Engineering practices. QED John Andreen Mark Zarella wrote: There is such a thing as "clean" and "dirty" power. A perfect case in point would be to run your amplifier with a cheap battery charger as its B+ supply. You will hear a tremendous amount of "hum". In other words, it is "dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 ) of automotive batteries in series. Tap the "GND" from the connection between battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the the top and bottom posts. to do this, you must eliminate the SMPS section and some other items. The Rectifying diodes and the bulk rail capacitors to be exact. You now have "clean" Power for your 400W/ch RMS amplifier. Many things can affect just how "clean" an amplfier is. Power supply topology, filter capacitors, Inductors, ferrite beads, transformer type, board layout, star grounding, trace capacitance, trace inductance, PCB layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a "clean" power amplifier. Do any one or all these things wrong and you now have a "dirty" power amplifier. There is even an extreme case where when the output rails do not have enough bulk capacitance, the output feedback circuit goes "open loop" for just a microsecond or so. In this time, the output transistors modulate or "burst" at their peaks causing audible distortion. Lots of cheap amplifiers will do this just before clipping at full power. Not all things are created equal. Power is one of them. If you want a mechanical analog, how about a V-8 piston engine and a jet turbine That's all well and good, but the important thing to examine here is whether the results are significant during normal operation. Hint: by significant, I mean audible. While there are several ways to lower distortion (sometimes at the expense of noise, or at the expense of reliability, or at the expense of other forms of distortion, and so forth), there is of course a threshold at which further reduction is not warranted, nor is it necessarily recommended since there's almost always a tradeoff in some manner or another. So your engine analog holds true, but if your application is to just drive down a road, then either one will perform as well as the other. |
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