FYI,:
Slew rate and frequency response can't be used to calculate the output voltage swing. The equation (slew rate = 2 * pi * Freq * Vpeak ) is used to calculate what slew rate you need to deliver a sine wave (of amplitude Vpeak at frequency Vpeak) without slew-induced distortion.
In other words, if you get an amplifier to deliver ever higher-amplitude and higher-frequency sinewaves, it will either run out of output voltage headroom, or it won't be able to swing the output fast enough. Which one happens first depends on whether the slew rate is respectively greater or less than 2*pi*Freq*Vpeak.
Cheers
IH
Slew rate and frequency response can't be used to calculate the output voltage swing. The equation (slew rate = 2 * pi * Freq * Vpeak ) is used to calculate what slew rate you need to deliver a sine wave (of amplitude Vpeak at frequency Vpeak) without slew-induced distortion.
In other words, if you get an amplifier to deliver ever higher-amplitude and higher-frequency sinewaves, it will either run out of output voltage headroom, or it won't be able to swing the output fast enough. Which one happens first depends on whether the slew rate is respectively greater or less than 2*pi*Freq*Vpeak.
Cheers
IH
IanHarvey said:
Slew rate of itself, can most certainly not be used to calculate an amps. Voltage swing....i think this development may have arisen out of a misunderstanding of post #975, where i questioned pan's suggestion that an 800V/uS slew rate was prima facie a 'good' thing with respect to sound quality.......
.....for this to be the case, an amplifier with a norminal slew of 800V/uS would have to swing well over 6Kv at its output for slew rate to become a cause of audible impairment.
mikek said:
...I have absolutely no difficulty with this gentleman's approach....
...spot on in all respects....cheers
I agree with you on this one mikek, good post and I feel about the same as this gentleman. Makes me feel warm inside to see that you and I can share the same views
/Peter
mikek said:
Not so sure I did suggest anything, only said that the best sound I´ve heard has been from power amps with very high "raw" slewrate and BW.
LC Audio Patriot and Zapsolute 4MHz/1MHz, Patriot having 1 degree phase shift at 20kHz and slew 800V/uS.
Dynamic Precision more than 250V/uS
The cheap LM3886 even though it in a simple circuit lacked some qualitys, still was very good.
I do not suggest that 4MHz BW and 800V/uS is necessary for an power amp to be "perfect", however I have never heard any other amp handle high frequencies as good as the
no-feedback 100W class A Patriot V100.
/Peter
More on slew
Since infinite slew rate would be a perfect amplifier (zero signal delay at output => input phase = output phase), I have to assume that slower amplifiers are less desirable.
I'm still trying to figure out if there is a way to measure the linearity of the slew rate and then correlating them to changes at the output. The value has a slope when graphed so the linearity must be measured in V/microsec^2.
Several questions come up...
1) Does the slew rate stay constant for the rated bandwidth or is the measured value some kind of average or median?
2) Does current draw (speaker impedance @ specific frequencies) affect slew rate? What other factors?
3) What is the minimum value for 20-20K?
4) How do tubes, transistors, and power opamps compare?
Also, I was curious so I checked the specs on the Bryston 7B. This is considered to be a very good amplifier and it seems that 60V/us is more than enough.
http://www.bryston.ca/7bsstspec.html
IM and THD+n are the same at .005% @ 8ohms 20-20K
Noise floor is 110dB 20-20K
Slew rate is 60V/us
Damping Factor of 300
ensen.
Since infinite slew rate would be a perfect amplifier (zero signal delay at output => input phase = output phase), I have to assume that slower amplifiers are less desirable.
I'm still trying to figure out if there is a way to measure the linearity of the slew rate and then correlating them to changes at the output. The value has a slope when graphed so the linearity must be measured in V/microsec^2.
Several questions come up...
1) Does the slew rate stay constant for the rated bandwidth or is the measured value some kind of average or median?
2) Does current draw (speaker impedance @ specific frequencies) affect slew rate? What other factors?
3) What is the minimum value for 20-20K?
4) How do tubes, transistors, and power opamps compare?
Also, I was curious so I checked the specs on the Bryston 7B. This is considered to be a very good amplifier and it seems that 60V/us is more than enough.
http://www.bryston.ca/7bsstspec.html
IM and THD+n are the same at .005% @ 8ohms 20-20K
Noise floor is 110dB 20-20K
Slew rate is 60V/us
Damping Factor of 300
ensen.
pp, I think you're confusing time domain and frequency domain parameters. It's meaningless to ask what a slew rate is at a given frequency.
For the record, slew rate is a time domain parameter, measured by inputting a step function and measuring the slope of the amplifier's time domain response. V/us, not us^2. The slew rate can be calculated from an amp's bandwidth, too.
Better slew rate = better amplifier is true to a point. What that point is is a matter of some discussion. Measured slew rates of real-world audio signals are surprisingly low. IIRC, Nelson Pass published some results on this, indicating that the power amp was being asked to slew at most in the single digit V/us range.
For the record, slew rate is a time domain parameter, measured by inputting a step function and measuring the slope of the amplifier's time domain response. V/us, not us^2. The slew rate can be calculated from an amp's bandwidth, too.
Better slew rate = better amplifier is true to a point. What that point is is a matter of some discussion. Measured slew rates of real-world audio signals are surprisingly low. IIRC, Nelson Pass published some results on this, indicating that the power amp was being asked to slew at most in the single digit V/us range.
Sorry, I get cranky when I type with a hangover!!
I may not have known the purpose for which the test was perfomed, but we all certainly knew what you were inferring it meant ..... so, I'm sorry you didn't like it but I believe my original statement stands.
Unfortunately this thread is full of statements (not referring to Pan per se here) like "this is a fact because I know it is a fact", "I know what I hear", "I don't need to do blind tests because ..... blah blah".
The scientific merit of these statements amounts to nothing, zip, nada, zero! The only thing these statements achieve is to define the author as poorly educated, mis-informed, or dare I use a stronger term, a fool.
Let's just take one statement on it's own, "I know what I hear - therefore I am right". Crap!
The amount of scientific evidence supporting the influence of psychological factors on sensory perception is overwhelming. Anyone arguing that they are "above" these influences and they can separate in their own mind "real" from "perception" by training is living in a dream world.
Again, I have NOT stated that member x/y/z cannot hear differences. I am stating that every single member on this forum is subject to the limitations of the human race, ie. subjective factors do influence our perceptions, like it or not.
I am not stating cheap amps sound the same as million-dollar amps, I haven't compared them in a properly blinded fashion and WAY back at the begining I outlined that this would then only refer to me, not another person, or a community as a whole. The question at the beginning was, "are blinded tests a valid method?"
And the answer is ....... still ....... YES
We need to dissect-out the method from the subsequent claims ......... many of which I acknowledge cannot really be made from the available data.
mark
I may not have known the purpose for which the test was perfomed, but we all certainly knew what you were inferring it meant ..... so, I'm sorry you didn't like it but I believe my original statement stands.
Unfortunately this thread is full of statements (not referring to Pan per se here) like "this is a fact because I know it is a fact", "I know what I hear", "I don't need to do blind tests because ..... blah blah".
The scientific merit of these statements amounts to nothing, zip, nada, zero! The only thing these statements achieve is to define the author as poorly educated, mis-informed, or dare I use a stronger term, a fool.
Let's just take one statement on it's own, "I know what I hear - therefore I am right". Crap!
The amount of scientific evidence supporting the influence of psychological factors on sensory perception is overwhelming. Anyone arguing that they are "above" these influences and they can separate in their own mind "real" from "perception" by training is living in a dream world.
Again, I have NOT stated that member x/y/z cannot hear differences. I am stating that every single member on this forum is subject to the limitations of the human race, ie. subjective factors do influence our perceptions, like it or not.
I am not stating cheap amps sound the same as million-dollar amps, I haven't compared them in a properly blinded fashion and WAY back at the begining I outlined that this would then only refer to me, not another person, or a community as a whole. The question at the beginning was, "are blinded tests a valid method?"
And the answer is ....... still ....... YES
We need to dissect-out the method from the subsequent claims ......... many of which I acknowledge cannot really be made from the available data.
mark
limitations of the human race
Why do you consider this as a limitation? We are not machines and as such we shouldn't negate the subjective experience. After all that's the beuty of being alive. And if it's even supported by overhelming scientific evidence, why not treated as a natural way we perceive sounds?
mefinnis said:
Why do you consider this as a limitation? We are not machines and as such we shouldn't negate the subjective experience. After all that's the beuty of being alive. And if it's even supported by overhelming scientific evidence, why not treated as a natural way we perceive sounds?
Re: SLEW RATE AND DYNAMIC RANGE.
Really liked some 300B´s from audion a number of years ago. Came home and in the end I thought my set up was not that far from the tube set up. I used an Holfi amp that was single ended until the outputstage so I guess I had some of the 2nd harmonic magic and also the "benifit" of a simplistic signal path.
A couple of years later heard the ARC VT100mk1/mk2 and compared it to Aleph5, almost got me hooked again but I waited for a while and ended up trying the GamuT D200 which I compared to ARC VT100, D200 bettered the VT100 in all aspects so the ARC was out. Of course the choice of speaker affects the result but I only had the possibility to try out so many speakers.
And.. since my good old Zapsolutes was equal or better than the D200 in my set up (allthough very different beasts) I still use the Zap´s. Thinking on trying a Dynamic Precision and a LC Audio Patriot at home again i my current system. Would also be fun to try a battery powered "gainclone" in triamp fashion.
Thanks for the tip about OTL´s, I have read many good things about them and will try to check out some more about them if I can find any in Stockholm. What´s the output impedance from a well designed OTL? I don´t wanna end up with a EQ in front of my speakers
Thanks!
/Peter
fdegrove said:Hi,
Peter,
High time for you to move into the thermionic camp...
From what I read so far, I think you'd like the way they can sound...you seem to be the perfect candidate for an OTL amp.
Cheers,
Really liked some 300B´s from audion a number of years ago. Came home and in the end I thought my set up was not that far from the tube set up. I used an Holfi amp that was single ended until the outputstage so I guess I had some of the 2nd harmonic magic and also the "benifit" of a simplistic signal path.
A couple of years later heard the ARC VT100mk1/mk2 and compared it to Aleph5, almost got me hooked again but I waited for a while and ended up trying the GamuT D200 which I compared to ARC VT100, D200 bettered the VT100 in all aspects so the ARC was out. Of course the choice of speaker affects the result but I only had the possibility to try out so many speakers.
And.. since my good old Zapsolutes was equal or better than the D200 in my set up (allthough very different beasts) I still use the Zap´s. Thinking on trying a Dynamic Precision and a LC Audio Patriot at home again i my current system. Would also be fun to try a battery powered "gainclone" in triamp fashion.
Thanks for the tip about OTL´s, I have read many good things about them and will try to check out some more about them if I can find any in Stockholm. What´s the output impedance from a well designed OTL? I don´t wanna end up with a EQ in front of my speakers
Thanks!
/Peter
Mefinnis wrote:
"I may not have known the purpose for which the test was perfomed, but we all certainly knew what you were inferring it meant ..... so, I'm sorry you didn't like it but I believe my original statement stands."
No, you are still wrong since the test I did was of use!
"Unfortunately this thread is full of statements (not referring to Pan per se here) like "this is a fact because I know it is a fact", "I know what I hear", "I don't need to do blind tests because ..... blah blah".
The scientific merit of these statements amounts to nothing, zip, nada, zero! The only thing these statements achieve is to define the author as poorly educated, mis-informed, or dare I use a stronger term, a fool.
Let's just take one statement on it's own, "I know what I hear - therefore I am right". Crap!"
The scientific merit of such statements can be very valuable.
Hehe, funny you don´t mention me but according to you I seem to look like a poorly educated, mis-informed fool. Wel well, I can live with such nonsens. And it´s not crap to say "I know what I hear- therfore I´m right" as it can be very true.
A number of years ago I started to learn that there was a significant audible difference between some audio products. I sometimes heard a difference and sometimes not. My friend suggested that I would not be able to hear the differences in a blind test , so we started to do blind tests and it turned out that EVERY TIME and for every component that I said that I could pick out in a blind test, I also COULD pick it out. This simply indicates that my hearing and ability to differentiate between components are VERY reliable.
"The amount of scientific evidence supporting the influence of psychological factors on sensory perception is overwhelming. Anyone arguing that they are "above" these influences and they can separate in their own mind "real" from "perception" by training is living in a dream world."
This is pure BS! I may be influenced in such a way that I think that I will hear this or that from a new component after reading the audiopress, BUT in the end it turn out;
1- I don´t hear a diffrence at all even though the new gear was very $$$
2- I hear a difference but the outcome is the opposit of what the press or add says.
3- I do hear a diffrence and it is in line with the common opinion of the product.
And no, I do not live in a dream world but my whole life has been about questioning the accepted beliefs and "truth´s" and learn to critically analyse the "reality" and learn to thrust my own ability in different situations. Sure there are "blind sheep" in this world, just don´t assume that everybody is such weakminded easy fooled persons.
"I am not stating cheap amps sound the same as million-dollar amps, I haven't compared them in a properly blinded fashion and WAY back at the begining I outlined that this would then only refer to me, not another person, or a community as a whole. The question at the beginning was, "are blinded tests a valid method?"
And the answer is ....... still ....... YES"
Yes, they are a valid method I feel so good ending this post with an agreement.
Happy listening!
/Peter
"I may not have known the purpose for which the test was perfomed, but we all certainly knew what you were inferring it meant ..... so, I'm sorry you didn't like it but I believe my original statement stands."
No, you are still wrong since the test I did was of use!
"Unfortunately this thread is full of statements (not referring to Pan per se here) like "this is a fact because I know it is a fact", "I know what I hear", "I don't need to do blind tests because ..... blah blah".
The scientific merit of these statements amounts to nothing, zip, nada, zero! The only thing these statements achieve is to define the author as poorly educated, mis-informed, or dare I use a stronger term, a fool.
Let's just take one statement on it's own, "I know what I hear - therefore I am right". Crap!"
The scientific merit of such statements can be very valuable.
Hehe, funny you don´t mention me but according to you I seem to look like a poorly educated, mis-informed fool. Wel well, I can live with such nonsens. And it´s not crap to say "I know what I hear- therfore I´m right" as it can be very true.
A number of years ago I started to learn that there was a significant audible difference between some audio products. I sometimes heard a difference and sometimes not. My friend suggested that I would not be able to hear the differences in a blind test , so we started to do blind tests and it turned out that EVERY TIME and for every component that I said that I could pick out in a blind test, I also COULD pick it out. This simply indicates that my hearing and ability to differentiate between components are VERY reliable.
"The amount of scientific evidence supporting the influence of psychological factors on sensory perception is overwhelming. Anyone arguing that they are "above" these influences and they can separate in their own mind "real" from "perception" by training is living in a dream world."
This is pure BS! I may be influenced in such a way that I think that I will hear this or that from a new component after reading the audiopress, BUT in the end it turn out;
1- I don´t hear a diffrence at all even though the new gear was very $$$
2- I hear a difference but the outcome is the opposit of what the press or add says.
3- I do hear a diffrence and it is in line with the common opinion of the product.
And no, I do not live in a dream world but my whole life has been about questioning the accepted beliefs and "truth´s" and learn to critically analyse the "reality" and learn to thrust my own ability in different situations. Sure there are "blind sheep" in this world, just don´t assume that everybody is such weakminded easy fooled persons.
"I am not stating cheap amps sound the same as million-dollar amps, I haven't compared them in a properly blinded fashion and WAY back at the begining I outlined that this would then only refer to me, not another person, or a community as a whole. The question at the beginning was, "are blinded tests a valid method?"
And the answer is ....... still ....... YES"
Yes, they are a valid method
I feel so good ending this post with an agreement.Happy listening!
/Peter
The Two Peter's .......
Sorry guys, couldn't help that, it was one of my absolute favourites (Sellers and Ustinov - "The Flat Earth Society").
Peter, try reading what I wrote over a thousand posts ago:
http://www.diyaudio.com/forums/showthread.php?postid=148996#post148996
I have no personal difficulty with accepting that "total perception" is the real requirement - I have stated this clearly (I think - and more than once)
Where I have difficulty with many of the authors in this thread is their absolute inability to accept that their own perception is subject to environmental influence, and the only way to assess what parts are "environmental" and what parts are "purely sonic" is to remove some of the former by blinding.
Now ... having done this we can assess the relative merits of the device in question. Would I be prepared to spend more money for an amp that sounded exactly the same (to me only - please!). Possibly yes if the aesthetics etc appealed. My own Aleph5 is an example in point.
What this allows us to do is weight the relative merits of devices more accurately ....... I have never, and will never suggest that environmental factors are not important to us.
Alas, no, it isn't BS and there we will have to agree to differ.
For the con, we have Peter's claims of his own ability - impressive. For the pro, try typing "psychoacoustics" into your favourite search engine. The resulting pages are of variable quality, some I acknowledge are pretty average, however hidden amongst the 13500 hits on Google is what I would term, "overwhelming support" that the effects do exist.
I'll let the reader decide ......
cheers
mark
PS: Actually, there have been a few people claiming they are not subject to environmental influences on their own perception, so the "con" is understated in the above, my apology.
Sorry guys, couldn't help that, it was one of my absolute favourites (Sellers and Ustinov - "The Flat Earth Society").
Peter, try reading what I wrote over a thousand posts ago:
http://www.diyaudio.com/forums/showthread.php?postid=148996#post148996
I have no personal difficulty with accepting that "total perception" is the real requirement - I have stated this clearly (I think - and more than once)
Where I have difficulty with many of the authors in this thread is their absolute inability to accept that their own perception is subject to environmental influence, and the only way to assess what parts are "environmental" and what parts are "purely sonic" is to remove some of the former by blinding.
Now ... having done this we can assess the relative merits of the device in question. Would I be prepared to spend more money for an amp that sounded exactly the same (to me only - please!). Possibly yes if the aesthetics etc appealed. My own Aleph5 is an example in point.
What this allows us to do is weight the relative merits of devices more accurately ....... I have never, and will never suggest that environmental factors are not important to us.
Alas, no, it isn't BS and there we will have to agree to differ.
For the con, we have Peter's claims of his own ability - impressive. For the pro, try typing "psychoacoustics" into your favourite search engine. The resulting pages are of variable quality, some I acknowledge are pretty average, however hidden amongst the 13500 hits on Google is what I would term, "overwhelming support" that the effects do exist.
I'll let the reader decide ......
cheers
mark
PS: Actually, there have been a few people claiming they are not subject to environmental influences on their own perception, so the "con" is understated in the above, my apology.
Re: The Two Peter's .......
What I'd like to agree on, is that although two amps may seem to sound the same in a blind test to a person, they might not sound the same in subjective environment, the one we are accustomed to in our usual way of listening and this should be treated as "real" reality, more important than just aesthetics. This might not appeal to everybody and of course is not the same to everybody, but in some ways it's real.
If there is some truth to what I just wrote, the blind test is useful for nothing more than just proving that we are indeed not perfect, but I am not sure if that's a limitation or an advantage.
mefinnis said:
What I'd like to agree on, is that although two amps may seem to sound the same in a blind test to a person, they might not sound the same in subjective environment, the one we are accustomed to in our usual way of listening and this should be treated as "real" reality, more important than just aesthetics. This might not appeal to everybody and of course is not the same to everybody, but in some ways it's real.
If there is some truth to what I just wrote, the blind test is useful for nothing more than just proving that we are indeed not perfect, but I am not sure if that's a limitation or an advantage.
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