John Curl's Blowtorch preamplifier part II

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scott wurcer said:
(snippage)in the beginning was way oversold like some of the early press on Kaman's two-wheeler.

Way oversold indeed. Back when I was going training development
and interactive stuff, Sharp started advertising a new display. They
showed this thing projecting a foundry pouring, sparks and all.

This was around 1985 and I was stunned at the quality, I called
Sharp and wanted to buy it along with a a lot of stock.

The advertising was fake, the thing wasn't projecting anything
in the ad at all...the ad agency was using a a pic of the foundry
in the ad copy along with a pic of the projector and did it during
their set up process.


John, sorry to read about your eye problems. I'll keep you and
them in my prayers.
 
Joshua_G said:
Hello John,
Good to see you.
What exactly do you mean by Quadrature?

Joshua,

I would imagine John is talking about the following:

Quadrature

and

QAM

Interestingly the latter has a pic of a Vector Scope screen, used
in TV production.

Wow, I never understood what the fundamentals were behind it
but the wiki does a damn good job of it for the choromanance information, I and Q.

and everybodies favoriate, Fourier, yeah.

The second article also talks about PSK in the intro and I think
that was used in the some of the early TADIL links. I think it
also plays a role in some of the G3, G4 stuff now too.

I kind of see the implications of it, but it is way over my head.

Here is one for the the following:


mouse

interesting...
 
SyncTronX said:
Joshua,
I would imagine John is talking about the following:
Quadrature
and
QAM
Interestingly the latter has a pic of a Vector Scope screen, used
in TV production.
Wow, I never understood what the fundamentals were behind it
but the wiki does a damn good job of it for the choromanance information, I and Q.
and everybodies favoriate, Fourier, yeah.
The second article also talks about PSK in the intro and I think
that was used in the some of the early TADIL links. I think it
also plays a role in some of the G3, G4 stuff now too.
I kind of see the implications of it, but it is way over my head.
Here is one for the the following:
mouse interesting...

I'm having trouble visualizing what these links might have to do with analog audio amplification. Is this really what John was cryptically hinting at? I guess we'll never really know.

Oh well, another night of troubled sleep while the brain tries to fit Quadrature into the big analog puzzle... :xeye:
 
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Perhaps he is referring to differential phase and differential gain measurements. That is what screws up good color rendition in an analog color video system. Its also not easy to measure or fix.Diff Gain and Diff Phase is a real good introduction to measuring the errors. And everyone has an HP8753D sitting around don't they? (I have access to a newer version and I may try to set up the test per their drawing.)

The concept will help understand aspects that feedback may not hide. The audibility of these remains to be studied.
 
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To fill in the blanks a little more this is a phenomena where the gain and phase of the amplifier changes as a function of the input DC level. It also changes per the signal level. It can be seen as a form of intermodulation but not easily measured that way. The normal measurement is done at the color subcarrier (3.58 MHz in the US). Not many audio products can pass that high a frequency.

Its also conceivable that the modulation can happen at much lower frequencies and interact with transient signals. I'm not sure how to measure that at all but it may be possible that a 100 Hz signal could get phase modulated by a DC shift. If the shift is at 1 Hz seeing the sidebands would be very difficult.

The core question that will be argued (not by John, he has other more pressing things to deal with) is the effect of the open loop rolloff of the opamp on this. Does the integration inside the loop affect the timing of the signals passing through it?
 
1audio said:
To fill in the blanks a little more this is a phenomena where the gain and phase of the amplifier changes as a function of the input DC level. It also changes per the signal level. It can be seen as a form of intermodulation but not easily measured that way. The normal measurement is done at the color subcarrier (3.58 MHz in the US). Not many audio products can pass that high a frequency.

Its also conceivable that the modulation can happen at much lower frequencies and interact with transient signals. I'm not sure how to measure that at all but it may be possible that a 100 Hz signal could get phase modulated by a DC shift. If the shift is at 1 Hz seeing the sidebands would be very difficult.

The core question that will be argued (not by John, he has other more pressing things to deal with) is the effect of the open loop rolloff of the opamp on this. Does the integration inside the loop affect the timing of the signals passing through it?

Thanks 1audio. So when you start phase modulating the signal
that is when yoiu start getting distortion and muddying up of the
bass, in a 100 Hz - 1 Hz signal range.

One on the things I found interested was that Quadrature is used
in control systems., with out going to the link...What I immediately thought when i read that, the two signals are 90 degrees apart,
is that it must be as two dimensional surface X,Y. Then I thought,
holy ****, they don't need a Z axis, fbecause if i understand GPS just by using the time delay you calculate z axis, or the 3rd dimension.

A ha, and if you follow the link, well you have the mouse, one examp
of using QAM. Stereo should be the same, just amplifiing music
or sound as opposed to a grid, or a planar surface.

Sorry guys if this is audio 101, or 102 class, this a new to me.

So, now I know what a sideband is eh? It is part of quadrature
that is 90 degrees off the carrier. Do you have two carries in
quadrature? or do you have one carrier and two side bands?

And if sidebands, then actually the sidebands are opposite from
each other, or 180 degrees offset.

Interesting, for me to understand more of this I have to relate it
to something I am familiar with. In the early days before, well I guess we could say at the end of analog, when there were laser discs the size of vinyl albums, we would use the video raster scan lines as a carrier and put an audio side band on it. This enabled you
to get 100s of hours of audio on a 1/2 hour video disc. I think the
follow on implementation became the MP3 format. Someone
got wise and must have checked some old patents.

Think about it, why else/how else would you have and MP3 (abbreviation for Moving Picture Expert Group, v3) as an
audio compression format?

Better stop now to get some accomplished here.
 
john curl said:
All that I can and will say, is that: Quadrature is everything in audio electronics quality.


MikeBettinger said:


I'm having trouble visualizing what these links might have to do with analog audio amplification.
Is this really what John was cryptically hinting at?
I guess we'll never really know.

We?

here is the Real problem > Lack of science education, in the USA >




http://www.boston.com/news/educatio...2007/10/16/poor_results_on_mcas_science_test/

http://www.businessweek.com/technology/content/mar2004/tc20040316_0601_tc166.htm

http://www.blackinformant.com/uncategorized/lack-of-math-science-teachers-prompts-us-alarm-usa-today


1153125
 
Actually Tom, there are very narrow creeks of a perfect broad science education in USA that is almost invisible on the background of a huge field of education of very narrow professionals needed to do kinds of modern businesses.
When USA is in need for more of scientifically educated professionals it opens gates for immigration of them. They create new technologies; colleges start preparation of new narrow professionals to use new technologies, then scientists loose their jobs but can't find anymore because colleges produced lots of narrow professionals who know how to explore that creations, and there are special questionnaires for recruiters that have a little in common with technologies, but help to determine how well college themes were remembered. However, creators of that technologies don't know what they should know about their creations in order to get jobs.
 
tomtt said:
We?
here is the Real problem > Lack of science education, in the USA >

It was just a figure of speach.

But, if I'm uneducated because I don't know what you know, isn't there something narrow minded in this? I think a bit more education would probably help you understand what is wrong with this assessment.

If this isn't what you meant, nevermind. If it was I’ll be careful not to personally include you in any my comments again and I also apologize to any other tender egos out there that I might have offended…

My real point was that it was a right field reference that I had not heard before, that will never be clarified and its significance to the music coming out of my speakers will remain as vague.

Hopefully John hits a home run with whatever he’s designing using this cryptic knowledge as guidance. Since you obviously understand what he's getting at I wish you happy listening as well. I'm assuming you do but the links don't really address the subject either.

I’ll just have to keep happily stumbling along with my "limited" education to guide me.
 
Wavebourn said:
Actually Tom, there are very narrow creeks of a perfect broad science education in USA that is almost invisible on the background of a huge field of education of very narrow professionals needed to do kinds of modern businesses.


narrow?

i suppose so ...

perhaps overly narrow.

When USA is in need for more of scientifically educated professionals it opens gates for immigration of them.


no country should have to do this .


They create new technologies; colleges start preparation of new narrow professionals to use new technologies, then scientists loose their jobs but can't find anymore because colleges produced lots of narrow professionals who know how to explore that creations, and there are special questionnaires for recruiters that have a little in common with technologies, but help to determine how well college themes were remembered. However, creators of that technologies don't know what they should know about their creations in order to get jobs.

i know how things go.

what i am saying, is that things should not go so poorly.

some of us may have heard the mass media say that we,

as humans, use only 10%, of our brains.

who here would agree, the real number, to be more like 0.002%.


1149430
 
MikeBettinger said:


It was just a figure of speach.

But, if I'm uneducated because I don't know what you know, isn't there something narrow minded in this? I think a bit more education would probably help you understand what is wrong with this assessment.



if this were about you and me, it would be narrow-minded.

but this is not about you or me.

this is about Everybody.

about going beyond the 'all too human',


and cattle drive/sheeple mentality.


If this isn't what you meant, nevermind. If it was I’ll be careful not to personally include you in any my comments again and I also apologize to any other tender egos out there that I might have offended…

see, this is offensive as well.

talking down, to someone that Knows Better.

almost every thing is offensive to me.

not the least, is an ability to live up to my own standards.

but that's not whats Really important ...


My real point was that it was a right field reference that I had not heard before, that will never be clarified and its significance to the music coming out of my speakers will remain as vague.

i know what you meant.

but here is The Point.

to be able to put things (those little clues) together.

and create, without being spoon 'fed.

Hopefully John hits a home run with whatever he’s designing using this cryptic knowledge as guidance. Since you obviously understand what he's getting at I wish you happy listening as well. I'm assuming you do but the links don't really address the subject either.

I’ll just have to keep happily stumbling along with my "limited" education to guide me.

like the Coleridge poem/Rush song -

"from an ancient book, i took a clue ..."

this is about thinking for ones self .

and how to put things together.

(those little clues ...)

This is the Home Run, that John wants ...


He wants YOU (and everyone) to succeed.


this is why people give him so much cr4p?

why would anyone do such a thing?


1153205
 
tomtt said:

I missed something here. I wasn't talking down. I was responding to the implication I was uneducated. Maybe a bit of sarcasim included for effect.

I know who I am and I've been reading the little cues for years. I don't talk down and my system sounds really good based on my reading the tea leaves, drawing my own conclusions and experimenting.
I wouldn't trade my approach for any of what I see coming out of the education system today.
 
MikeBettinger said:


I wouldn't trade my approach for any of what I see coming out of the education system today.

You are over-generalizing again. There is a lot of good professionals that is coming from an educational system today. However, most of them are trained for narrow thinking that is needed for steady day-to-day professional work, but some of them are very widely educated. However, Soviet system could afford very broad education so we used to say that "our research work is the way to satisfy own curiosity for government expenses", but it is unpractical in a free market economy that reacts on demand. But it's reaction is massive and delayed, that causes oscillations like in amplifiers with negative feedback.
 
Waste of words. Most cannot understand, others will not. I wish that I could help, but I am not able to. In short, classical op amps will always be problematic in audio amplification. Video amps have a good chance of being more successful. It is entirely due to the open loop bandwidth, high enough slew rate, and reasonably low distortion, especially higher order odd. That is all there is to it.
 
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