John Curl's Blowtorch preamplifier part II

[simon7000]

Originally Posted by bcarso

That's my understanding Ed, although I heard it second-hand --- I don't know Doug very well. From what I have heard about working for the folk at One Infinite Loop, in, as Larry Heyl used to say, the Land Without Adverbs ("Think Different"), I could well understand that it may not have worked out.

The folks I know at JBL is dropping with age and faster turnover. Doug was always a good dinner at trade shows. (I have been told I am down to just being a top 20 dealer. Once at a Crown show they had a new brochure. Looking at it I remarked that all the venues mentioned in the US were my projects. The president jumped up grabed an engineer and confirmed that.)

[simon7000]

Originally Posted by scott wurcer

Certainly no one is using 2" wafers, I don't think the starting material is available anymore (maybe for some very exotic devices). We got a quote today for some specialty JFET's for an experiment $290 @ 1-9 in die form

My last batch of LM3X0 pieces were also marked 7915. They are measuring 20 dB PSSR @ 6k. That is why I was pleased to see similar results in Linear Audio. I expect as devices move to newer processes for the published parameters to improve. I will not show these measurements formally as too many folks don't understand that what today is the "best" part many not be next week and what was not impressive may get much better.

[john curl]

Richard, you really did get spoiled working for LLL. I remember 29 years ago,(1984) calling you up about a high voltage avalanche array that we used to control an optical shutter for a laser. My design info first came from previous work done at LLL or LBL, and when I described what I was doing, you sort of laughed that my approach was very antiquated or primitive, and that I should throw a lot of money at the new and 'better' approach then used.
You see, even though I was part of a design team making a medical laser, I did NOT have an infinite source of funds, and we were not building nuclear bombs, so we did not need more than the array of high voltage transistors to avalanche on trigger.
Yes, we made the 'primitive' controller work, and I saved the company some money.
It is much the same with custom jfets. It is RARE that one needs a custom sort of jfet, unless again, one is making extremely critical designs.
Also, the very idea that somebody will make a CUSTOM jfet for a few hundred dollars is equally absurd. Perhaps a special select of jfets is what is required.
In any case, it might be interesting to discuss how to use jfets more flexibly, so that we can still make pretty good audio circuits with relatively cheap and available jfets.

[RNMarsh]

Well JC, what size company has an R&D budget of $1 Billion a year? yes, spoiled burning thru 25 mill a month ( I didnt do it alone - had 5000 LLNL Scientists/engineers/techs/employess helping). Reaching beyond SOTA. Do that for 25 years and you get pretty far ahead of the game. Where do you think oil shale, retort and coal gasification R&D came from? Lasers and DNA computing and particle accelerators/colliders and all the rest? LLNL, Sandia etc. Hey. Someones got to do the hard risky stuff that results in technology transfers to industry.

Not a lot applies to audio and music, though. So, its been my hobby. I am for learning to use jFEt more flexibly. Whatya got for us? Thx-RNMarsh

[Esperado]

Originally Posted by RNMarsh

I didnt do it alone

You do not have the qualification to be a politician ?

[john curl]

I don't disagree with you, Richard. In fact, I had a little of that when I was with Ampex Research in 1969. I still have some planar power complementary transistors that I bought for an amp project, that cost something like $100 ea at the time. Mil quality, gold plated, stud mount, very fast. Those were the days!

[john curl]

The subject that I wanted to talk about is:
Using combinations of Jfets, with other parts, to make 'super parts' that may have even once been made, but it might be cheaper to series and-or parallel devices and get similar results. This concept goes back more than 40 years to the FETRON which was a vacuum tube replacement, composed of a low input capacitance jfet cascoded with a 200-400V jfet (available at the time) for the voltage holdoff. This was originally used to replace real vacuum tubes in VTVM's made by a number of companies.
Today, we might use a MOSFET, instead of the high voltage jfet to get similar results. Heck, today we could make a solid state direct drive for STAX phones with a dual jfet cascoded by a pair of 800V mosfets, and get pretty good results. There are more combinations that we could talk about.

[RNMarsh]

Originally Posted by Esperado

You do not have the qualification to be a politician ?

Almost -- I was a Sr. EE Technical Coordinator on some very large projects. Interfacing with a lot of people from a multitude of disiplines. Fortunately, I didnt have to get votes to keep my job! Just being really good at it was enough.

[john curl]

Richard, I just talked to Jack Bybee about his former project with the government.
He quoted 16 billion dollars for that project, so I asked him why so much? This was the project where we had to know where or quickly locate Russian Atomic missile subs under water before they could launch their missiles. We sort of 'got caught with our pants down', (not the first time) when the Russians one-upped us! Let me congratulate the USSR for doing so, at this much later time, quite a feat!
Anyway, we had to throw money at the problem, just like we did with going to the Moon. That is what made silicon valley so powerful and advanced in those days. You know: MONEY!

[jacco vermeulen]

One might think that a Sr. EETC on SVLP is good enough for politics.