Are you sure ? It seems that you published perfectly right things, 1/3 century ago. Things we knew before, if you worry about our technical level.
When you are right, why do you want us to critic you ?
Again, you comments about slew-rate are curious. Slew-rate reflect the open loop bandwidth, or, better, the speed of the feedback. There is a minimum required: the slew-rate of the input signal = slew-rate of the amp. Each increase of the amp's speed provide better results, both on the measurements, and on the listening experience. Reason why 1000V/µs. Because things are not perfect, the faster, the better. So complicated to understand ?
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Yes it is difficult, Esperado, because we worked for 10 years, from 1970-1980 before we had TIM and its relationship to slew rate, fully nailed down. You may be right that faster is better, all else being equal, but slew rate is not everything.
Also, I might personally agree with you that open loop bandwidth and the 'speed of feedback' might increase, but try to convince others here that this is important. Good luck!
Of course, IF you had read 'Solomon', instead of complaining about its length or difficulty, you would have come to understand that a higher slew rate NUMBER only indicates better performance, ALL ELSE BEING EQUAL, but there are real exceptions to this rule, so an IC with 50V/us slew rate, might actually perform worse than one with 20V/us that has a more linear input stage.
Esperado, I regret to have to mention that my background in audio design runs rings around yours, so if I have a question for you, I usually know the answer already, but I am asking you to 'prove' it. Not 'complicated to understand'.
Also, I might personally agree with you that open loop bandwidth and the 'speed of feedback' might increase, but try to convince others here that this is important. Good luck!
Of course, IF you had read 'Solomon', instead of complaining about its length or difficulty, you would have come to understand that a higher slew rate NUMBER only indicates better performance, ALL ELSE BEING EQUAL, but there are real exceptions to this rule, so an IC with 50V/us slew rate, might actually perform worse than one with 20V/us that has a more linear input stage.
Esperado, I regret to have to mention that my background in audio design runs rings around yours, so if I have a question for you, I usually know the answer already, but I am asking you to 'prove' it. Not 'complicated to understand'.
This slew-rate story is not complicated to understand if we take cars example.
(This apply everywhere a servo is used)
You follow a little car with your own. The little car will accelerate and break at various moments as much as it can.
If you use the same car, at each acceleration or break, you will have a distance (distortion) witch will vary between this car and your, due to the delay of your reflexes, and the impossibility to accelerate or break faster.
. If you use a formula one, and faster reflexes, the error distance will be reduced a lot.
This explain the 1000V/µs.
Now, the color of your car does not matter more than the sens or break-in of cables.
When John talk of color as a element of this equation, John will be flamed.
Now, if he believe to "runs rings around ours", talking about sens of cables, Bybee's quantum, sens of cables and other stupid audiophile superstitions, i believe his way to turn is not at all round.
(This apply everywhere a servo is used)
You follow a little car with your own. The little car will accelerate and break at various moments as much as it can.
If you use the same car, at each acceleration or break, you will have a distance (distortion) witch will vary between this car and your, due to the delay of your reflexes, and the impossibility to accelerate or break faster.
. If you use a formula one, and faster reflexes, the error distance will be reduced a lot.
This explain the 1000V/µs.
Now, the color of your car does not matter more than the sens or break-in of cables.
When John talk of color as a element of this equation, John will be flamed.
Now, if he believe to "runs rings around ours", talking about sens of cables, Bybee's quantum, sens of cables and other stupid audiophile superstitions, i believe his way to turn is not at all round.
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In connection here with slew rate, recall Demian's remarks and others about settling behavior (not just what the limiting slope in overload is, which is amply discussed in Solomon for the traditional topology of diff stage with at most steered tail currents into an integrator). The issue of symmetry comes up as well, and the low-frequency shifts associated with high level signals when it fails to obtain.
You don't have to explain it to me Esperado, try to explain it to everyone else. For example, why over 100V/us for just about anything? Where oh where are the input signals that need this sort of rate-of-change? What trade-offs do you get when you go faster than 20V/us for an IC?
Please don't get me wrong, IF you can and do have a preamp and a power amp that is 400-1000V/us good for you, one problem solved. However I have never personally been able to SHOW that a slew rate over 100V/us is necessary with ANY audio signal that can exist from source material. The microphones are just not that fast. I did not always think this way, and I built a 250V/ch power amp with a slew rate over 1000V/us for VMPS about 32 years ago. Would I do it today? No, not for audio.
Please don't get me wrong, IF you can and do have a preamp and a power amp that is 400-1000V/us good for you, one problem solved. However I have never personally been able to SHOW that a slew rate over 100V/us is necessary with ANY audio signal that can exist from source material. The microphones are just not that fast. I did not always think this way, and I built a 250V/ch power amp with a slew rate over 1000V/us for VMPS about 32 years ago. Would I do it today? No, not for audio.
Just look the bandwidth INSIDE the loop, after the feedback has been substracted to the input signal.
In my power amp, with 1000V/µs and 8Mhz of closed-loop bandwitch, there is an increase of the resulting signal above 2.5KHZ of 6DB/oct. To be perfect (flat bandwidth inside the loop), my amps should have 10 000V/µs.
John, i believe you miss the point. Of course, your pride keep you away from exploring this in more detail.
In the same time, you are the one who insists on the importance of high order/frequencies distortions. You're not bothered by contradictions.
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Don't you realize what a MIXAGE between several instruments can do, and what kind of speed can out of a DAC between two samples ?
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Thanks for the last preprint John. I read the earlier paper and that is interesting. With all that super sonic hash it almost seems you are better off with a moving magnet for that simple reason though I understand that is only part of the picture. It would seem a safe bet to filter the output of the moving coil before it ever got past the phono stage and entered the preamp section of the circuit.
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