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Old 1st October 2012, 03:05 PM   #951
SY is offline SY  United States
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Originally Posted by CPaul View Post
You are simply begging the question: assume a model that requires balance.
No, it requires equal loads; balance is the result, not the constraint. You're putting words in my mouth again. Please refrain from that.
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Old 1st October 2012, 03:27 PM   #952
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There is no imperative to assume a model that is capable only of handling a balanced case. That was your choice. The proper approach is to model the general case and then investigate specific ones, not jump to the conclusion you want and declare the model has proven itself. Rose tinted goggles again.

I'm describing what you're doing, not quoting you. There's a difference.

I've proven your model measures Zpk, not Zpg nor Zkg. You have provided no basis on which to make assertions about the latter two.

Willful ignorance of a proof, especially in the face of no attempt at its refutation, is no defense against its conclusions. For you, this proof is simply an inconvenient truth.
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Old 1st October 2012, 04:40 PM   #953
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I've proven your model measures Zpk, not Zpg nor Zkg. You have provided no basis on which to make assertions about the latter two.
Other than experimental verification as the circuit is actually used. When you stoop to doing an actual experiment, I'll re-engage. Until then, this is useless.
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Old 1st October 2012, 06:00 PM   #954
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There you go, threatening to run away from an inconvenient fact.

There is a thing called ďdesign of experiment (DOE).Ē Unless you know what youíre measuring, itís absurd to view bench testing as your salvation. There is no way to bench test a ďdesign of experiment.Ē You must actually think it through. Unless you do, youíre just flailing away with a soldering iron and test clips.

Iíve proven why your design of experiment to measure Zkg and Zpg was flawed, and that you were measuring Zpk instead.

When you actually design an experiment which measures Zkg and Zpg, it might be worth the trouble of bench testing it. But Iíd sure want to know why I couldnít analyze it before I went through the trouble.
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Old 2nd October 2012, 12:36 AM   #955
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It's also pretty ironic that you demand that I experimentally verify the Figure 2 double-Thevenin test circuit that you presented in your article with an algebraic argument!

I'll provide experimental evidence that your test circuit puts no current into ground when AC-shorting ground to the P and K if you'll agree that that means that it's not measuring the plate and cathode impedances to ground.

Deal?

Or is this "experimental verification" stuff just another red herring?
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Old 2nd October 2012, 01:36 AM   #956
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@CPaul, can you post your designs here so we can look at it?
....theories are fine, but for us diyer's we would rather see the outcome.....
as they say, the acid test of the pudding is in the eating.....
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Old 2nd October 2012, 02:13 AM   #957
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Quote:
And let's not get off on a red herring.
What you do in your spare time is your own business.

This whole discussion reminds me of Einstein trying to demonstrate that the Heisenberg uncertainty principle was false by constructing one thought experiment after another, all in vain. Why isn't there any discussion of the oscillograms from the original article that show the circuit to be intrinsically balanced?

John

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Old 2nd October 2012, 02:57 AM   #958
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Originally Posted by CPaul View Post
KenPeter, I'd like to take a look at the 908 circuit and get a better feel for it. I think it'd be best to start with the simpler case, without global feedback, and then add it back in.

Do you have any thoughts about the difference between its operation and that of the earlier circuit with no caps bypassing the transformer? I guess the bandwidth of the newer one would be better.

Hope the beer was good. You don't mix that with soldering irons, do you?
Difference that the first sim transformer coupled. And that transformer
phase splitting (non-intentional) would have invalidated the Cathodyne
experiment. There was also 2K2 damping in the signal path to prevent
the resonant LC tank (also non-intentional) from ringing.

The second moves 2K2 damping out of the signal path, and helps the
transformer look more like resistors to GND for audio frequencies, but
a short circuit to GND for DC. Cap coupling is dominant, and perhaps
close enough to a traditional setup to test some theories.

But there are yet a few minor problems holding back the experiment.
Both have the closed global negative feedback loop that needs to go.
And need to figure how we can dial cathode feedback from unity to 1/Mu
without ruining DC bias for cathode, or presenting uneven resistance for
the split.

What the beer lacked in quality was more than made up in quantity.
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Old 2nd October 2012, 03:00 AM   #959
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jlsem, I like your humor!

The Cdyne with identical P & K loads has equal and opposite P & K voltages (is that what you mean by "intrinsically balanced"?) It has to. Since the current going into the plate must come out the cathode and the loads are equal, Ohmís Law demands this. There is no need to invoke Cdyne electrode impedances to obtain this outcome.

Tony, I'm pretty much a theoretical kind of guy. Iíve written a number of articles for Audio Amateur/xpress and EDN over the years. That, and maybe (re-)discovery and popularization of the Mu Follower have been my contributions. I find the analyses and derivations of circuit performance to be fascinating. That's probably why it's so important to me to get the basics right. If youíre looking for me to impress you with my designs, Iím afraid thatís not going to happen.
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Old 2nd October 2012, 03:25 AM   #960
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Originally Posted by CPaul View Post
Since the current going into the plate must come out the cathode and the loads are equal, Ohmís Law demands this. There is no need to invoke Cdyne electrode impedances to obtain this outcome.
I fully agree with you, but where is the error in the Preisman Article then ?
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