Mike is referring to me here saying that I don't have the facts right.mikeks said:
I was refering to J.Curl's assertion that 0.5V/uS/V equates to 50V/uS for 100W. This is clearly incorrect......
http://www.diyaudio.com/forums/showthread.php?postid=530065#post530065
http://www.diyaudio.com/forums/showthread.php?postid=530671#post530671
So get your facts straight..... 🙄......
.........I did not refer to anything you posted....at all...
100W, 8 ohms = 40 Vpeakjohn curl said:
0.5/us/(2*40) = 40 us/V = John is right!
Peak to peak = top positive voltage - top negative voltage
Mike K, it's clearly that you don't understand what we are saying, nor do you try to _explain_ your statements. John Curl _is_ right if you understand him.mikeks said:
The reason I started this thread was that amp_man had a real fantastic definition of slew rate demands for PA use. I have tried here to put up valid formulas so everyone calculate for themselves.
So Mike, have you anything to add more than saying everybody is wrong?
Marc Vi. said:
I remember it is extremely difficult to hear even 180 degrees difference (reversed speaker leads, both sides) on music. Maybe we have different memories?
Jan Didden
Marc Vi. said:
Marc has the right idea, and the simple rule of thumb is as follows:
Design for PBW=200kHz for near 0 degrees phase shift @20kHz
Therefore, SR = 2 PI Vp Fmax
for 400W into 8 Ohm---> SR = 2PI (80V)(200k) = 100V/us
for 100W into 8 Ohm---> SR = 2PI (40V)(200k) = 50V/us
Input filter should be 1 or 2 MHz.
Darren
z_p_e said:
Your formula is OK, yes. The rest is hearsay, speculation and completely separated from reality.
Jan Didden
peranders said:
Dear me!!... 😀...
OK John said:
john curl said:
...and my response was:
mikeks said:
....and John's reply:
john curl said:
To which i replied:
mikeks said:
Definition:
SR/uS=2*pi*f*V(peak)*1*10^(-6)
Additionally:
SR/uS/V(peak)=SR/uS/V(peak-peak)
i.e: You do NOT multiply the Rate of change by 2 to obtain the rate of change for the peak-peak value for the same waveform......
Slew rate for a sinusoidal waveform is determined from its peak value....
A usefull analogy:
If a car travels at constant speed for a given distance, the speed at which it travels will not double because it has travelled TWICE the distance....!!!!!!!!!!!!!!!!!!!!! 🙄
.ends
Peranders...
You really.....really need to read this more thoroughly:
http://www.national.com/ms/LB/LB-19.pdf
Cheers
You really.....really need to read this more thoroughly:
http://www.national.com/ms/LB/LB-19.pdf
Cheers
Jan,
It ‘s really difficult to hear a reverse polarity of the speakers, that’s true. Some studies, which a never read myself but found references to more than 20 years ago, say that:
- we can hear a variation of 0,2 dB within a octave which means that the – 3 dB band width must be very much larger;
- we can hear frequency components above 20 kHz from frequencies below 20 kHz (non-linear behavior of hearing for intermodulation products);
- we can hear the phase relations between two tones and the deviations of the phases of more than 10 (and not 5) degrees.
That all means that the bandwith of an amplifier must be, starting from a first order filtering, from about 3 Hz to 120 kHz.
Marc.
It ‘s really difficult to hear a reverse polarity of the speakers, that’s true. Some studies, which a never read myself but found references to more than 20 years ago, say that:
- we can hear a variation of 0,2 dB within a octave which means that the – 3 dB band width must be very much larger;
- we can hear frequency components above 20 kHz from frequencies below 20 kHz (non-linear behavior of hearing for intermodulation products);
- we can hear the phase relations between two tones and the deviations of the phases of more than 10 (and not 5) degrees.
That all means that the bandwith of an amplifier must be, starting from a first order filtering, from about 3 Hz to 120 kHz.
Marc.
Marc Vi. said:
Mark,what you say, I understand your reasoning.
But:
- I do not agree that we can hear .2dB within an octave with MUSIC. You can probably design some very clever single tone test that statistically shows that probably you can hear under specific circumstances .2dB blabla etc. But that's no reason to design an amp to that spec!
- some with your second assumption
- same with your third assumption.
What I find amazing is that somebody (I'm not specifically aiming at you) says he heard something from somebody who read it 20 years ago and whoopy! we need to design lighspeed amps.
Those people advertising 500V/uSec amps are laughing all the way to the bank!
Jan Didden
Jan,
The articles I am referring to are:
Lipshitz, J.A. and J. Vanderkooy, “The great debate: subjective evaluation”, JAES, vol. 29, july/august 1981, p. 482-491.
Dtodolsky, D.S., “The standardization of monaural phase”, IEEE, vol. AU-18, no. 3, September 1970, p 288-299.
Madson, E.R. (et al), “Threshold of phase detection by hearing”, paper of 49th. AES convention, Rotterdam, 1973.
Craig J.H. and L.A. Jeffres, “The effect of phase on the quality of a two component tone”, JASA, vol. 34, 1962, p. 1752-1760.
Indeed these references are (very) old. I designed and build amplifiers more than 20 years ago. I wrote an article (in Dutch) in RB Elektronica Magazine of October and November 1989, in which I described the state of art of all kinds of solid state analog audio (end)amplifiers at that moment.
Recently I picked up my old hobby. In the meanwhile digital electronics has changed the world!! To my surprise and disappointment, in solid state analog audio amplifier design there is not so much news under the sun, on the contrary. I see the same circuits (and the same faults) as 20 years ago. I see the same references to old (but good) design principles of Self, Hood, Hawksford, Borbely and so on. Now we have some faster/better (power)transistors (like from Sanken) and faster/better opamps (like OPA 627) but that’s all.
In the 80ties of the last century it was already quite simple to design an amplifier with a bandwidth from 3 Hz up till 100 kHz and a slew rate of 50 V/usec. Nowadays it is even hard to design an amplifier with less than that for a normal HiFi use in a living room. I do not mean amplifiers for disco’s and it is not my intention to make those people advertising 500 V/usec laughing.
Marc.
The articles I am referring to are:
Lipshitz, J.A. and J. Vanderkooy, “The great debate: subjective evaluation”, JAES, vol. 29, july/august 1981, p. 482-491.
Dtodolsky, D.S., “The standardization of monaural phase”, IEEE, vol. AU-18, no. 3, September 1970, p 288-299.
Madson, E.R. (et al), “Threshold of phase detection by hearing”, paper of 49th. AES convention, Rotterdam, 1973.
Craig J.H. and L.A. Jeffres, “The effect of phase on the quality of a two component tone”, JASA, vol. 34, 1962, p. 1752-1760.
Indeed these references are (very) old. I designed and build amplifiers more than 20 years ago. I wrote an article (in Dutch) in RB Elektronica Magazine of October and November 1989, in which I described the state of art of all kinds of solid state analog audio (end)amplifiers at that moment.
Recently I picked up my old hobby. In the meanwhile digital electronics has changed the world!! To my surprise and disappointment, in solid state analog audio amplifier design there is not so much news under the sun, on the contrary. I see the same circuits (and the same faults) as 20 years ago. I see the same references to old (but good) design principles of Self, Hood, Hawksford, Borbely and so on. Now we have some faster/better (power)transistors (like from Sanken) and faster/better opamps (like OPA 627) but that’s all.
In the 80ties of the last century it was already quite simple to design an amplifier with a bandwidth from 3 Hz up till 100 kHz and a slew rate of 50 V/usec. Nowadays it is even hard to design an amplifier with less than that for a normal HiFi use in a living room. I do not mean amplifiers for disco’s and it is not my intention to make those people advertising 500 V/usec laughing.
Marc.
Marc Vi. said:
Hi Marc,
Just checked my library, I don't think I have your article.
I have some of the references you quoted, and as far as I remember they studied things like phase audibility in isolation, like your ref. from Madsen. But it is a long way from using that to conclude we need less than 5 or 10 deg of phase shift at 20kHz to get good reproduction! Have you ever checked the phase response of your speakers??? Do you listen with your head in a vise to keep it from moving, lest you ruin your phase response?
I agree that we still see the same stuff of 20 years ago, in fact you see it all being re-invented on this forum. Why is there no progress? I am not sure, but possibly one factor is that whatever we do from the current state of the art, it will not improve audibly our systems. We are going around in circles. There are so many different concepts and implementations, that ALL sound *good*.
And yes, it is easy to design for 100kHz BW and 50V/uSec, but remember the window rule: the larger the window, the more junk flies in. Some people say we need to design for 500kHz or more with 100's of V/uSec slew rate. Well, they built so fast amps that they need a faraday cage to run it in. Is that in the interest of audio? I don't think so, it is an interesting exercise engineering wise.
Jan Didden
Hi Jan,
You may be right that those articles deal with hearing phenomena in isolation. And yes, speakers do have a phase shift and when we move our head, there is also a phase difference. (BTW there is much more progress in speaker design than in amplifier design: speakers do sound much better than 20 years ago).
For me it only means that designing an amplifier, I take as a safe starting point a BW up till 150 – 200 kHz with a input filter of about 100 kHz.
In the next week I will make a pdf-file of the original of my article in RB Elektronica Magazine and I will place it in a new Thread and/or I mail it to you.
Marc.
You may be right that those articles deal with hearing phenomena in isolation. And yes, speakers do have a phase shift and when we move our head, there is also a phase difference. (BTW there is much more progress in speaker design than in amplifier design: speakers do sound much better than 20 years ago).
For me it only means that designing an amplifier, I take as a safe starting point a BW up till 150 – 200 kHz with a input filter of about 100 kHz.
In the next week I will make a pdf-file of the original of my article in RB Elektronica Magazine and I will place it in a new Thread and/or I mail it to you.
Marc.
Marc Vi. said:
Hmm, is the idea that the amp can't get a signal driving it into slewrate limits ?
MikeB said:
I think the idea here is to get the amp so fast that it cannot get into slew rate limiting no matter what. If you look at the real audio signals coming off the source into the amp, you can get by with much lower specs. And it still sounds good!
Jan Didden
Mike,
Yes, the goal of the input filter (just a R and a C) is that the amplifier cann't be driven into slew rate conditions, as you see in almost all amplifiers.
Marc.
Yes, the goal of the input filter (just a R and a C) is that the amplifier cann't be driven into slew rate conditions, as you see in almost all amplifiers.
Marc.
And are you sometimes thinking about saturation, respectively about " avalanche " of saturations by overload, gentlemen ? And about antisaturation circuity, about recovery times and about settling time. Good amp don't make only SR and low distortion, but all these parametres together - do you realize, how often is " normal " 100 W amp by " normal " listening conditions overloaded ? Who here have in own amp clipping detector ? 😉
janneman said:
Jan,
What is wrong with designing an amp with minimal phase distortion?
Yes loudspeakers are still, and probably always will be the weakest link in the audio reproduction chain, but why add to the problem?
An amplifier designed to have near zero degrees phase shift at 20KHz is designed this way because we CAN do it. The ability to design a near perfect loudspeaker is still a long ways off, but that doesn't mean we should compromise the design of the components preceeding them.
It is difficult to understand the resistance to the design of wide bandwidth, and fast audio amplifiers, when if they are stable in their design, what harm is done?
Is it not better to know for certain that the amplifier is not slew limiting, nor adding phase distortion? It has been said that no proof can be or has been demonstrated that wide bandwidth and fast slew rate are required. I have not seen proof that demonstrates it is NOT required either.
Again, what is the harm done? Does a LM318 sound worse than a uA741?
Darren
There is nothing wrong with minimizing phase shift from an amp in itself, but doing so will force compromises in other areas. For instance, as has been pointed out earlier, extremely wide bandwidth means that more noise will be amplified. It also often means that open-loop gain must be reduced, which means increased distortion at lower frequencies.z_p_e said:
Even if phase shift in the uppermost octaves were really that important (you can test this yourself by inserting an all-pass filter - you will find that it takes quite a lot of phase shift before the effects on music are appreciable, assuming it's equal on both channels), the fact that loudspeakers give a 180 degree phase shift at higher frequencies compared to lower frequencies clearly reduces the relative importance of the amplifier's contribution.
The uA741 does not meet the minimum requirements for audio, so it's a bad example. Anyway, as I said, increasing the performance in one area will necessarily lead to compromises in other areas. It is important to know how far one parameter can be improved before the point of diminishing returns is passed.
- Status
- Not open for further replies.