Wavebourn said:
I didn't relize I was over generalizing again, but your right, it sounds that way. Although I was referring to my specific experiences with a significant number of younger educated engineers in my day to day functions. It's the rare one that's been taught how (or has the ability) to do and most Excel at PowerPoint engineering; probably aced the MS suite classes.
I didn't intend for this to spiral out like this. John made a comment about something I could not relate back to audio circuitry in the vague hope he might throw out some point of reference to allow me to dig deeper into the concept. He says most cannot/will not understand, yet provides, as I originally pointed out, nothing other than a cryptic reference. Now a few words trickle down mentioning video op-amps. Great, that frames the thoughts for me and I'll leave it at that.
So he is correct, this has been a waste of words.
john curl said:
Because some designers of audio amps don't see results of own creations, so they are free to follow traditions, while designers of video amps don't have such privileges so they are free to use "non-standard" and "non-traditional" topologies to get results, while the same schematic ideas that lead to wide bandwidth, low phase and amplitude distortions in video amps, would make audio implementations happier. And what is called "transients" in audio in video reality is the usual plain signal that has to be taken care of.
How would we measure the phenomena we are talking about? How would it evidence itself? Diff gain and diff phase is one way but what is the direct consequence of the "quad mod" problem? is it something we can look at directly in a way that could "map" to a cognitive process in the hearing mechanism? For starters what kind of timing sensitivities exists in hearing? Phase response? Close in IM sensitivity?
I can measure some pretty esoteric properties but its helpful if the measurements are relevant.
I can measure some pretty esoteric properties but its helpful if the measurements are relevant.
It sounded more philosophical than it is meant to be. if I measure the delay through a circuit at a certain frequency to +/- 20 pS and change the DC and see a change of 60 pS it may not matter since its not conceivably audible or its not the thing to measure to show the effect we are looking for.
Think of this as traditional research- hypothesis, analysis, design experiment that will test the hypothesis, run experiment, check results against the hypothesis and see if they can be duplicated.
Think of this as traditional research- hypothesis, analysis, design experiment that will test the hypothesis, run experiment, check results against the hypothesis and see if they can be duplicated.
Hi John, all
Quadrature
I hope you don’t mind a drive by post, I think about and miss the days when I worked with active electronics.
I would take a guess about quadrature etc.
My guess is that your referring to the real and imaginary components, phase shift between voltage and current when driving a reactive load, like potential and kinetic energy.
Since the open loop upper frequency corner is often set by capacitances, it turns out that one could make wider bandwidth amplifiers by making them a current amplifier and not a voltage amplifier.
As of the early 90’s (when I switched to working on only passive electronic circuits), many of the video or higher op amps were current amplifiers.
If one has an amplifier who’s open loop corner were well above 20KHz, I am not sure I see where there could be much improvement though.
In the old days, I had convinced myself that a degenerated circuit with the desired gain, distortion and impedance would generally outperform a conventional closed loop circuit. On place where the difference stood out was when you paralleled the output with a capacitor.
With the degenerated circuit, a square wave looked like it as passed though an RC low pass filter, with the R being the output impedance, this seemed to me to be correct.
With negative feedback, the square wave had the normal ringing which suggested that the output didn’t look like a pure resistor at all.
Where my work on this stopped was in looking at amplifiers from the output side.
With the input grounded, through a “load resistor” I drove the output of the amplifier under test and compared the drive signal to the residual on the amp terminals.
My thought was that the amplifier terminals in a perfect amplifier would be a “stiff ground” but in reality, they aren’t perfect.
Where these imperfections would be added to any output normally, but they are naked when there is no input signal and the amplifiers circuitry is trying to hold the output at “zero” in the face of changing signal current. Sort of a back emf view of the amplifier.
Anyway, I should stop rambling, I am probably off base anyway.
I hope your eyes get better, I have to get mine checked again next week to see what's up.
Best regards;
Tom Danley
Danley Sound Labs
Quadrature
I hope you don’t mind a drive by post, I think about and miss the days when I worked with active electronics.
I would take a guess about quadrature etc.
My guess is that your referring to the real and imaginary components, phase shift between voltage and current when driving a reactive load, like potential and kinetic energy.
Since the open loop upper frequency corner is often set by capacitances, it turns out that one could make wider bandwidth amplifiers by making them a current amplifier and not a voltage amplifier.
As of the early 90’s (when I switched to working on only passive electronic circuits), many of the video or higher op amps were current amplifiers.
If one has an amplifier who’s open loop corner were well above 20KHz, I am not sure I see where there could be much improvement though.
In the old days, I had convinced myself that a degenerated circuit with the desired gain, distortion and impedance would generally outperform a conventional closed loop circuit. On place where the difference stood out was when you paralleled the output with a capacitor.
With the degenerated circuit, a square wave looked like it as passed though an RC low pass filter, with the R being the output impedance, this seemed to me to be correct.
With negative feedback, the square wave had the normal ringing which suggested that the output didn’t look like a pure resistor at all.
Where my work on this stopped was in looking at amplifiers from the output side.
With the input grounded, through a “load resistor” I drove the output of the amplifier under test and compared the drive signal to the residual on the amp terminals.
My thought was that the amplifier terminals in a perfect amplifier would be a “stiff ground” but in reality, they aren’t perfect.
Where these imperfections would be added to any output normally, but they are naked when there is no input signal and the amplifiers circuitry is trying to hold the output at “zero” in the face of changing signal current. Sort of a back emf view of the amplifier.
Anyway, I should stop rambling, I am probably off base anyway.
I hope your eyes get better, I have to get mine checked again next week to see what's up.
Best regards;
Tom Danley
Danley Sound Labs
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