Basically, there is just ONE nonlinear transfer function for the circuit examined. Some methods reveal more, some less, and it is much about ability to assess results. Yes, CCIF IM or THD20k say quite a lot.
Anyway, there are other influences, not discovered by this kind of analysis. These are especially PSRR (EMI through PSU) and RFI. For PSRR, supply rails have to be considered as circuit inputs.
Regarding the 2nd issue, I have a nice instrument at my disposal now, it is Rohde-Schwarz FSP7 spectrum analyzer.
Anyway, there are other influences, not discovered by this kind of analysis. These are especially PSRR (EMI through PSU) and RFI. For PSRR, supply rails have to be considered as circuit inputs.
Regarding the 2nd issue, I have a nice instrument at my disposal now, it is Rohde-Schwarz FSP7 spectrum analyzer.
@John and Bob (and Edmond and Ovidiu, for that matter):
I just couldn't resist...
- Klaus
An externally hosted image should be here but it was not working when we last tested it.
I just couldn't resist...
- Klaus
bear said:
It's unlikely for simple circuits to have a patholgical differences between simulation and reality. Once you have enough interacting parameters, I don't see how soldering and un-soldering numerous components and taking measurments at each step is anything but time consuming and error prone and actually not all that fun either.
Charles Hansen said:
Yes!, thank you Charles to clarify things, as you pointed out I misinterpreted your comment about feedback for the specific Wilson current mirror, and I thought it was directed also to my circuit, assuming you were talking about feedback as "degeneration", (sorry)!
It’s why I was so confused.Thank you again for all these hints.
john curl said:
Thanks, John. Understood. Yes, Editors can get us into trouble.
I did mention the 14-page rebuttal in the post. I have never been able to find the copy of it. You have it, but are reluctant to share it. I have the lengthy letter I wrote in response to your rebuttal (I think you provided it to me), but of course that never got published either.
Its hard to discuss the merits of a 14-page rebuttal that can't be made available, so we should just drop it unless you want to make it available. I have already offered to make mine available.
I think we should just leave that all in the past. Life is too short.
Cheers,
Bob
Charles Hansen said:
Everyone that steps up to the plate with an opinion is trashed by those who either don't understand what was said, don't want to know what was said, or don't want to believe what was said, etc...
If you ever had the opportunity to hear the original Theadra and original Ampzilla, together, you would understand where his place in audio history is.
From the simple engineering side, if you compared those designs to the lion's share of what was available at the time they stood out as properly engineered products; with all aspects considered and intelligent compromises made.
Yes he's a characture, he told me I was hearing things when I commented on a clearly audible change in the sound of the Theadra lineamp as they struggled to refine the design to keep up with demand. I said OK. (interestingly traced to the change in the differential FETs).
I learned alot working with his designs. He's deeper than the quick pan of his career that just occured.
I was thinking that anything that might in effect magnify or help discriminate between circuits or circuit variations in the simulation would or might be valuable given that the levels are often reasonably small...
the ability to see the vanishingly small higher harmonics more clearly might be useful?
Of course I have rarely been accused of actually thinking...
_-_-bear
the ability to see the vanishingly small higher harmonics more clearly might be useful?
Of course I have rarely been accused of actually thinking...
_-_-bear
john curl said:
I figured you did, my comments were for the less knowing (curious) in the audience. I wasn't commenting on his latest stuff, I can tell by looking at the execution what the limitations are. My comments were based on the original Theadra/Ampzilla combination, when new.
Once again, the bear sitting in the woods analogy must mean something to someone, and I'm sure their laughing their Ars off right now.
lumanauw said:
I don't think that's the case. The thing is that there was some correspondence from many years ago, but it was co-authored by several people and perhaps intended to be private. So John cannot simply publish it without getting the OK from everyone involved. He's not deliberately being mysterious.
MikeBettinger said:
Don't be so quick to jump to unwarranted conclusions.
I've heard his old stuff. I worked at a shop (as a repair tech) that was one of the very first Ampzilla dealers there was. (This was after he stopped selling the kit and decided to make it into a commercial venture.)
The Ampzilla was a very good amplifier in its day. In fact, it was probably the overall best sounding solid state amplifier until the Leach amplifier was developed a few years later. (And that's not quite fair, as Leach never built his amp. He just made the instructions, so each builder's version varied slightly due to the parts used -- some Leaches were better than the Ampzilla and some weren't.)
The Ampzilla was one of the first fully complementary amps out there. At that time there was an argument as to whether Bongiorno was first or whether Daniel Meyer (Southwest Technical Products Corporation -- SWTPC) was first with his (Tiger) series of amps in Popular Electronics that culminated with the Tigersaurus.
In truth, I think that John Curl was first. It's just that he didn't publish his designs until years later as retribution against Mr. Mark Levinson who didn't honor his agreements with John Curl.
Bongiorno also was one of the first proponents of the "servo", whereby the feedback loop includes DC gain to keep the offset to low levels. At the time, all of this sounded very esoteric and mysterious. We were all sure that JB was a brilliant designer.
And given that background, where I held him in such high esteem, is exactly why my opinion of him dropped a few notches after reading the Audio Amateur article in question. If I thought he was a know-nothing, it couldn't have dropped. But I did think he was was an innovator. But after reading that article I realized that he didn't know as much as he thought he knew.
That doesn't take away from his accomplishments. It simply changes my personal assessment of his contribution to the art of audio reproduction. It's kind of like movies. Everyone has their favorite movies, perhaps a top ten list. And maybe every once in a while you see a new movie that bumps one of the old ones out of the top ten. Or perhaps more to the point, maybe one of your top ten movies was a remake of something that you had never seen the original of. Then when you saw the original and understood that the remake was only a pale imitation, then maybe the remake dropped out of the top ten (and maybe even out of the top 100).
Everyone has their own assessment as to the contributors to amplifier design. And I don't think that anyone could dispute that James Bongiorno made a valuable contribution to that art. All I said was that my personal opinion changed after reading that article. YMMV.
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