John Curl's Blowtorch preamplifier part II

gpapag · 2013-01-16 7:05 am

jcx said:
for sure it can be frustrating - but also an opportunity for all to improve their explanatory skills, even their understanding

so far this particular back and forth appears quite the model for what I would like to see here more often in technical discussions/disputes

much better than personal attacks, "black bag" rhetorical twisting of every word, appeal to inscrutable, conveniently unavailable "authorities"...

I hope that my “questioning” of jn distortion on the freq level falls under jxc umbrella.

It’s not that I have any real EM theory knowledge.
It’s not that I dispute jneutron knowledge on this and his capacity to dig on something others haven’t.

It is that there are at least two areas that this effect had a very high chance and good reason to be observed and studied by theoreticians and highly skilled engineers but it hasn’t.
The two areas are 1 coaxial cables, 2 Integrated circuits (ICs)
There are other areas as well (micro strip PCBs, miniaturized wave guides as used with slot phase array antennas and many other constructions in which AC voltages and minute conductor’s physical dimensions are met).

IMO, if there is one case which lends itself in precise theoretical modelling and controlled experimentation , this is the coaxial line.
Test of theory, test of material properties influence on the effects.

Can we start from there?

George

Bonsai · 2013-01-16 7:45 am

RNMarsh said:
What's involved in annealing transistors (fets)? Could it be attempted outside a manufacturers lab?
-Thx RNMarsh

It's quite a normal semiconductor process. But the equipment is specialized and you need to do it at the right stage in the manufacturing process. I've never heard of annealing done in packaged devices.

Anneal temp will vary based on what you are trying to actually anneal.

gpapag · 2013-01-16 10:13 am

SY · 2013-01-16 10:38 am

RNMarsh said:
What's involved in annealing transistors (fets)? Could it be attempted outside a manufacturers lab?
-Thx RNMarsh

Unless you have the raw chips, you'll just cause a huge amount of contamination from degradation of the epoxy and siloxane adhesives.

sofaspud · 2013-01-16 11:32 am

Anneal temp will vary based on what you are trying to actually anneal.

I've spent a little time in a CVD (chemical vapor deposition) & annealing clean room. Wafers are placed on quartz carriers and sent into a tubular oven that's glows red hot inside. Most semiconductors are finished with a passivation layer (for protection) and pad mask etch (for external connections).

Esperado · 2013-01-16 1:13 pm

a.wayne said:
People with bad stereo , bad hearing or both , usually take to laughing at audiophiles and their choices ...

While Audiophiles have so good hearing that they are even able to listen to things that does not exists. On fantastic stereos made of two 13cm full range speakers on precious wood flat panels powered by a huge 3Watts Class A amplifier they can use to heat their home.

At least unwashed people have time to listen to music while his audiophile neighbor is listening endless the same 10 seconds samples of old worn vinyls, trying to figure out the changes brought by some new magic golden cone to the reproduction of the silence after Herbert von Karajan stopped to wave his arms.

The researchers tried to invent special drugs to treat them: "Blind tests". It was a failure, This disease is incurable. And expensive: with just the money they spend for their power cables, you can feed 10 African villages and their marabouts.

However, i can have good time, inviting two of them for a dinner and enjoy. or just, sometimes, reading your contributions to science and your appreciation of my stereo system (you've never heard) on DiyAudio.com.

gootee · 2013-01-16 3:14 pm

<Grin!>

marce · 2013-01-16 3:34 pm

Very funny but astute

scott wurcer · 2013-01-16 3:36 pm

RNMarsh said:
What's involved in annealing transistors (fets)? Could it be attempted outside a manufacturers lab?
-Thx RNMarsh

Basicly no the temperatures involved would destroy later processing and/or the package, we had a physics professor claim he could but when we talked he was claiming he could remove all noise. One rule NEVER ever sign an NDA with kooks.

EDIT - You also need something to getter what you want to remove, even scratching the backside worked somewhat then backside argon implant was better. With DI you might need topside gettering, all need to be part of the process.

magnoman · 2013-01-16 3:39 pm

gpapag said:
IMO, if there is one case which lends itself in precise theoretical modelling and controlled experimentation , this is the coaxial line.
Test of theory, test of material properties influence on the effects.

Can we start from there?

George

George
At least for the current crowding effect being discussed wouldnt the co-ax symmetry prevent it all together?

Thanks
-Antonio

DF96 · 2013-01-16 3:55 pm

Coax symmetry is not the problem. The issue with coax is that the spacing between inner and outer is large enough that normal skin effect dominates. Now I believe that skin effect and proximity effect are merely auto and mutual versions (respectively) of the same thing so will behave in the same way, but I am not sure everyone agrees so demonstrating nothing strange with skin effect might not convince those looking for strange proximity effects.

You would probably need to setup something where conductor spacing is smaller than skin depth so proximity effect dominates, as may sometimes be the case for audio. Maybe an air-cored inductor or transformer, but with well-encapsulated windings so no physical movement is possible?

bcarso · 2013-01-16 4:08 pm

scott wurcer said:
One rule NEVER ever sign an NDA with kooks.

Earnest inventors often wonder why large companies turn them away when they show up at the door with big grins and "great new ideas".

My other favorite are the calls I get from people with "great ideas" who in essence wind up saying "with my great idea, and your expertise to make it work, we'll split 50-50 and both get rich!"

Esperado · 2013-01-16 4:25 pm

bcarso said:
Earnest inventors often wonder why large companies turn them away when they show up at the door with big grins and "great new ideas".

Don't they realize the simple fact they ring the door's bell is an insult to the manager of the company and the money he invested in the R&D department ?

mikelm · 2013-01-16 4:44 pm

Don't the managers realise that their "not invented here" closed minded attitude probably loses them some unique opportunities - other side of the coin

Esperado · 2013-01-16 4:55 pm

I agree, with the eyes stuck on daily work and efficiency requisites, a R&D department is often the worse place to get innovative ideas. Even if it is in your nature to look at the things upside down. Part of the Peter principle.

gpapag · 2013-01-16 5:39 pm

magnoman said:
George
At least for the current crowding effect being discussed wouldnt the co-ax symmetry prevent it all together?
Thanks
-Antonio

Antonio , as DF96 said this symmetry is not the problem.
The "current crowding" effect in the coaxial expresses itself as current concentrating at the outermost of centre conductor’s diameter and at the innermost of shield’s diameter. At both conductors, the cross-sectional current carrying area diminishes.

DF96 said:
Now I believe that skin effect and proximity effect are merely auto and mutual versions (respectively) of the same thing so will behave in the same way

This is my understanding too

but I am not sure everyone agrees

That’s an invitation for discussion

The issue with coax is that the spacing between inner and outer is large enough.

The beauty and convenience of theoretical approach is that this distance can be made minute. Distortions (if any) can be theoretically derived. Effect of radial distance increase up to a real physical size can be calculated.

On the theoretical level of approach, the study is done on the cross section of the coaxial line, i.e. a slice having an axial length dL.
If result are then integrated over a length 1000dL or 100000dL the calculated distortions at the dL slice will I guess be multiplied accordingly (?).

Then, a good length of a coaxial cable with a small diameter (e.g. RG58) can be used in experiments to test the theoretical predictions.

George

john curl · 2013-01-16 5:41 pm

I remember back in 1975 while attending an AV convention in Montreux, I tried to interest Neve 'engineers' in my measurements of the ceramic caps that they were using in their modules at the time. I got a big affront telling me that everything they do is a 'trade-secret' and they don't wish to discuss any new input. '-)

scott wurcer · 2013-01-16 5:44 pm

magnoman said:
jn,

That would help but I think I'm following your basic argument just not quite how it produces a second.

If one accepts the dI/dT dependency and that this effect only increases the crowding resistance then I can understand how for a sinewave this would result in cos modulation from the dI/dT and the absolute value to account for only increasing resistance.
But from there I see this modulation producing steeper slopes around the cross-overs, local minimums at the peaks, all symmetrical between positive and negative going cycles of the sinewave. Why wouldn't this symmetry measure as a dominant 3rd?

Real or not at least for a series feedback divider the effects should cancel out (between the high side and low side resistors).

Thanks
-Antonio

Well easy enough to plot the FFT's, for an R = Ro(1 + a*abs(cos(wt)) there are all even harmonics but sin(wt)/(Ro(1 + a*abs(cos(wt)) ) is all odd. Where a is some very small factor.

SY · 2013-01-16 5:47 pm

Esperado said:
I agree, with the eyes stuck on daily work and efficiency requisites, a R&D department is often the worse place to get innovative ideas. Even if it is in your nature to look at the things upside down. Part of the Peter principle.

That one has me scratching my head in puzzlement. The barrier to accepting ideas thrown over the transom (besides the obvious, that most of them are a colossal waste of time) is that if the idea is a good one, you're 99.99% certain to end up in expensive litigation even if it's an idea that already existed within the company. I've worked in and run several different R&D organizations and there's no shortage of really interesting and original ideas that come out of them.

bcarso · 2013-01-16 5:55 pm

SY said:
That one has me scratching my head in puzzlement. The barrier to accepting ideas thrown over the transom (besides the obvious, that most of them are a colossal waste of time) is that if the idea is a good one, you're 99.99% certain to end up in expensive litigation even if it's an idea that already existed within the company. I'veworked in and run several different R&D organizations and there's no shortage of really interesting and original idea that come out of them.

Litigation, or rather its avoidance, is really the key here. It is sooo expensive, in money but especially in time, even if you "win". And there is a natural but often unjustified notion that the "big" company is simply at fault to begin with. Sometimes they are, and being big does often engender arrogance and worse. But the romantic paradigm of the little guy getting the helical inclined plane (or however the writers of Big Bang Theory put it) is also not always accurate.

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