John Curl's Blowtorch preamplifier part II

[Steve Eddy]

Originally Posted by janneman

See attachment here:

http://www.diyaudio.com/forums/showp...postcount=1010

I posted it to help JC to remember what he wrote 30+ years ago ;-)
This is from the same paper as Fig 3.

Ah, ok. They were just talking about the regular intermod series. I thought you meant they'd actually identified some of those peaks as specifically being what you'd labeled them.

Thanks for the clarification.

se

[Wavebourn]

Originally Posted by Steve Eddy

Ah, ok. They were just talking about the regular intermod series. I thought you meant they'd actually identified some of those peaks as specifically being what you'd labeled them.

As John Curl once said, they've found an asymmetry of sidebands. I.e. heights of strips are different while in case of pure IM they should be equal, that means additionally to IM there is some PM.

[john curl]

Thanks for reminding them, Wavebourn, but the sidebands are symmetrical, which implies FM. However, back then, while I was a participant in the original testing, 34 years ago, I did not notice these 'extra' pips as being anything special, either, until the possibility of FM modulation was pointed out to me, recently.
I think that Matti first mistook the added pips to be the 2F2-NF1 series, because the 2F2-9F1 seemed to fit fairly closely. It is just that some of them DON'T fit closely enough. It was just the wrong path to take, but all pioneers go up 'blind alleys' some of the time. Everyone, please understand that.
In those days, before personal computers, and the smallest practical computing device was the PDP-11, we didn't use computers at all, and this test was performed by an HP3581, and some sort of mechanical plotter.
It is a good machine, but all analog, so far as I know. I have one sitting in my closet, and I loaned SY one, years ago. He still has it, I guess, and unless he decided to use it for a 'boat anchor' or door stop, it still does a respectable job of measurement.

[Wavebourn]

Sorry John, I misunderstood you. I thought you were referring to asymmetrical pips that may signify presence of PIM, but I don't understand how some extra pips may signify PIM. For more than 2 pips to be visible in case of PM there should be horrible deviation that can't be produced by the device in question. And as soon as both IM and PIM present pips should have different height, due to compensation.

[john curl]

It is really easy to see this. Just print out Fig 3, especially at 2 times size, then FOLD IT BACK, on itself around F1 or 3.18KHz. You WILL find symmetry in the contested distortion byproducts. This hint is due to Jocko, a former contributer here, and still one of the best engineers I know.

[Wavebourn]

Originally Posted by john curl

It is really easy to see this. Just print out Fig 3, especially at 2 times size, then FOLD IT BACK, on itself around F1 or 3.18KHz. You WILL find symmetry in the contested distortion byproducts. This hint is due to Jocko, a former contributer here, and still one of the best engineers I know.

That means, no PIM is visible, if pimps are of the same height.

[john curl]

Wavebourn, FM modulation, itself, has pips of EQUAL height. I have it running in my lab. Please, don't predict what should or should not be. What is, is what matters.

[Wavebourn]

Originally Posted by john curl

Wavebourn, FM modulation, itself, has pips of EQUAL height. I have it running in my lab. Please, don't predict what should or should not be. What is, is what matters.

Why I should not predict John if I know what happens when PIM and IM are mixed together? Do you remember, I told you that I've experimented with different kinds of distortions in order to create musical signals? Do you remember I told you that when I made PIM device for a bass guitar nobody liked the sound because it was horrible? I learned radio and electronics then, trying to apply knowledge to synthesis of sounds and sound effects. We did not select which disciplines to take; it was impossible since an education system was carefully planned and everything prescribed was compulsory. I wish we had a choice, in such case I would take more of related to radio and electronics disciplines instead of humanitarian ones, like CPSU History, Philosophy, Economics of Socialism, and so on. I barely remember Economics of Socialism. But I remember well how to create SSB using a phase modulator. Just mix them in proper proportion until one pimp and a carrier disappears. When proportions are in between pimps have different heights.

[syn08]

Originally Posted by Wavebourn

That means, no PIM is visible, if pimps are of the same height.

Pimps are only coincidently of the same height and usually are not FM or even AM. We have quite a few here in Toronto downtown around Jarvis St.

[Wavebourn]

Originally Posted by syn08

Pimps are only coincidently of the same height and usually are not FM or even AM. We have quite a few here in Toronto downtown around Jarvis St.

No matter how do you cal that strips on the paper, but it is a forum. Be it a democratic institution we could vote for PM or against PM, be it a tribe we could ask our Elders to decide, but here on the forum some physical evidences have to be presented. I believe that PIM were present in that experiment because I know how to create it, but I don't see a proof of it's presence on the graph.