Fine, but the problem has often been addressed to uA741 like parts. That's probably not the case, and even much faster parts, generally used in audio and assessed as sufficient by many, are apparently not good enough for the purpose.
syn08 said:
How was the crossover distortion simulated using such a model is one of those deep mysteries
* NE5534 OPERATIONAL AMPLIFIER "MACROMODEL" SUBCIRCUIT
🙁 🙁 🙁
Tired, tired. Are we back to talking about how "we" proved in 1970 that 741's and 709's are not good for audio? Is this still important to talk about? And who did invent macromodels?
Surely not, but 5532, TL071 and devices slightly faster are considered good for audio by many and are used in most professional equipment in tens per unit.
5532/4 certainly show up in very recent audio DAC eval circuits where they're presumably competing for THD+Noise specs
I don't recall any showing the ccs pull down trick on the op amp output or in Vout DAC filter/buffers - many of the Iout DACs have a bias I offset on the I outputs
I don't recall any showing the ccs pull down trick on the op amp output or in Vout DAC filter/buffers - many of the Iout DACs have a bias I offset on the I outputs
scott wurcer said:
Don't know, but I suppose some lawyer, in a desperate attempt to "protect" your brilliant design ideas.
Flashnews: the bad guys have nitric acid, microscopes and microprobes. So what?
PMA said:
I like this idea very much!
Also, except AES there is one more organization, called BAF. It is more open for creatively thinking people, who like to experiment and draw own conclusions instead of following by approved standards.
Bring back TO cans! The 5532/4 is pretty long in the tooth. I can only imagine there are many sources driving the price down to pennies. All the specs have been topped by an order of magnitude for years.
jcx said:
The point is, in order to observe nastiness in questions the circuit in question has to be pushed in the directions to reveal that nastiness clearly. At least, I use such a method for years, to design an equipment that sounds clean way below conscious perception thresholds, hence no direct measurement in normal operations regime is possible.
Let me show you one my recent example, of a driver with 27 dB amplification factor, 50 mA standing current, 100 V P-P output.
Here is 500 KHz 100V P-P response with 6N2P input tube, looks highly asymmetrical (for my taste). However, it is way above officially accepted audio band, but anyway it is a symptom that indicates presence of some non-linear phase shifts. Since subconscious sensitivity to phase shifts is 1,000 times better than a conscious one let's improve it anyway. The less of distortions we add is the better.
The weak point was, of course, an input tube that drives a Miller capacitance of the output one. Here is the same 100V P-P, 500 KHz square, but with 6N1P tube, 8 mA standing current. Looks much better, except some overshoots. Now, even way beyond officially accepted audibility the amp performs much better:
Here is the same, with 10 pF capacitor in parallel with 12K feedback resistor:
And finally, 50 KHz squares, 100V P-P. I am satisfied. Now going to solder the 2'nd channel, the same. I tried to take 2 Hz squares, but my camera is too fast to take a picture. Nice symmetrical output (both in terms of phase and signal level) from an asymmetrical class A 2-stage amplifier. That means, the lower is the level the lower will be distortions. It is very significant because our perception is extremely sensitive to distortions of quiet sounds.
scott wurcer said:
As a bonus, this would make lots and lots of GEB members very happy. It is a known fact that opamps in TO99 sound so much better.
john curl said:
Hi John,
We'll have to agree to disagree on what happened. I'm not surprized that Matti had that perception. It is quite likely that Pat did say something like that to him, but the full context was probably that the paper could not go into the Journal if it was not adequately peer reviewed.
All of that is history, now. As I indicated earlier, you and I don't always remember the history in the same way.
BTW, if I am not mistaken, the Greiner paper may have been earliest in mentioning the desire for wide open-loop bandwidth. Nevertheless, I think it sells Matti and others short to assert that Greiner et al had it all figured out in the late 60's. The lively discussion surrounding Matti's work (on both sides of the argument) really moved the ball forward. We may not have agreed with everything Matti said, but he REALLY made us think.
I have also found that the AES has become less interesting, mainly to me because I liked the analog and instrumentation stuff. There is not too much of that these days. There are some interesting Class D papers in the pipes, however.
Cheers,
Bob
syn08 said:
It would be also interesting to find out what NE5532 model was used in that simulation. The only NE5532/NE5534 spice model I have ever seen is coming from TI and is one of those stupid behavioural macromodels, completely improper for any THD, TIM, DIM and any other three letter acronym simulations. In fact, the model is only a degenerated diff pair with resistive loads, everything else are synthetic voltage controlled voltage/current sources feeding the output and the common mode, and a 50ohm resistor to simulate the OL output impedance.
How was the crossover distortion simulated using such a model is one of those deep mysteries
Wow!! Did I ever make a mistake! I was not paying enough attention. When I wrote my post I was assuming that the pics were of a measurement, not of a simulation.
For something like this, I would be reluctant to put a lot of faith in the simulation.
Cheers,
Bob
bob:
i definitely agree with you there. i also haven't seen too many papers that interested me from aes in a while. when i use to work some place that had access to the older aes (and other) journals and papers, i found myself rereading those a lot.
mlloyd1
i am thinking i am not the only one who used to skip class in college reading tech papers in the library 😉
i definitely agree with you there. i also haven't seen too many papers that interested me from aes in a while. when i use to work some place that had access to the older aes (and other) journals and papers, i found myself rereading those a lot.
mlloyd1
i am thinking i am not the only one who used to skip class in college reading tech papers in the library 😉
Bob Cordell said:
mlloyd1 said:
Organization are similar to people: they grow, mature, decay, and die. BAF is young enough, so no bureaucracy and under-the-rug activity yet that is more significant than the main reason of existence of an organization, so let's go this October and meet in San Francisco.
scott wurcer said:
But - properly used - they still can sound very good with, especially, acoustic music and voice.😉
PMA said:
I mean, push to directions where errors that are usually below measurement and conscious audibility would show well, then deal with them, so when returning back to normal mode you know that that particular errors were taken care of, even when you could not measure them during normal operations, nor reliably find in controlled (say consciously perceptive) listening tests.
Here is an analogy.
Some engineers used their best equipment to convince themselves and their customers that according to their precise visual measurements the wheel is round so can't bump at all!
But customers keep saying that the wheel bumps!
What do they do?
One goes out of business, because he is too proud to admit that the customer really feels the bumps; another starts scientific activity to convince the world that those who feels the bumps are phools uneducated!
What do I do in this situation?
I am searching the way to make the wheel smooth!
Visual inspection does not show why it bumps.
So, I create the method to make smooth wheels, and create the method to test if they bump or not: I push wheels beyond their normal rotation speed and find that they really bump! But they bump because they are dis-balanced, that can't be caught by visual measurement instruments.
And now, after I made wheels that run smooth, they keep saying that other wheels that really bump have no reason to bump because they can't find the reason using their standard measurement equipment?
BV: As I have already said, there is a mixture of linear and non-linear distortions. It would be necessary to subtract the passed-thru-opamp square.
No , but maybe because they (reasonable)suppose that wheels should be used (an tested with e.g 3times reserve) at speed, that is real on real ways.
It is the same as to try to produce airplanes, that cannot be damaged by crash? They then cannot fly, i suppose..
Wavebourn said:
But to continue the analogy, the customers are not able to tell the difference between a wheel that bumps and one that doesn't. So what is the use of engineering ever rounder wheels? 😉
jd