Re: gEDA-user: C++ HDL

[Gene Heskett <gene.heskett@xxxxxxxxxxx>]

On Friday 15 May 2009, Dan McMahill wrote:
>John Doty wrote:
>>>> So will the 6L6, but few engineers ever have reason to design with
>>>> one.
>>>
>>> However, those who do make oodles of money. Audio freaks seem to have
>>> pockets of infinite depths.
>>
>> Sure, but so what? There's no need to train the average EE to do this
>> work.
>
>this thread has degenerated a bunch, but.... I would argue that the
>average EE *should* be able to design with a 6L6.  Actually, maybe
>something like a 12AX7 (triode) would be better.  Why do I say such a
>crazy thing?  Because if a school has done a decent job with its
>undergrad program than you should be able to go to an engineer with no
>experience using vacuum tubes, hand him/her the appendix from Gray and
>Searle that does a basic derivation of a triode operation, hand him/her
>a datasheet and a schematic and they should be able to right away
>analyze the circuit and tell you what it is and the basics of its
>performance.  A small signal model is a small signal model.  If you've
>drawn a load line the exact device at hand shouldn't matter.  If you
>understand the idea, the specifics are just that.  Details.  Minutia
>that can be relegated to a cheat sheet (brain swap space).
>
>That's the difference between a principles based program and an
>applications/memorization based program.
>
>-Dan

+10ee34, Dan.  That is one of the basic truths I learned long in the past. Its 
been 65 years since I picked up a hot soldering iron the first time in the 
early 1940's.  I had the principles by the time I quit school at the end of 
the 8th in '48 and went out to fix these newfangled tv's for a living.  Sure, 
I had to find some algebra and trig along the way, but the principles have 
_never_ let me down.

Too bad many don't grok that.  All the vacuum tube stuff has been relegated to 
the trivia games it seems, or as a sizzle the audiophiles can sell at 
outragious markups just because IFM.  But there are lots of side effects going 
on inside that vacuum that the younger people will never be exposed to.  I 
guess they work on the IFM principle when they see a 2A3, or a KT-66/KT-88.  A 
7788?  6336, or a 4-1000?

I still deal with most of those, till June 12th anyway since I'm in broadcast 
engineering.  As for the simplification of the triode, that is good for the 
groundwork but there are all sorts of secondary effects to plug in and account 
for when you start adding more grid wire shells and beam shaping electrodes.  
Efficiency and gain can go up, a lot, but it often comes at the expense of 
some pretty severe non-linearity's once you get out of the sweet spot.  So 
these guys _should_ need a semester on vacuum tubes just to make sure they 
have the principles, but they need to understand that the principles come with 
a pretty long 'case:' statement to get them well rounded.

Yeah, I think we are offtopic for sure, but that is often where some strong 
opinions about basic truths can be found.

BTW, some of the tube stuff I see now when the garage bands tune up, would 
quite rightly have been called junk in the 1950's.  It is plumb amazing what 
they will spend a weeks wages on.  We sold better stuff for $12.95 back then.  
Full of microphonics and popcorn noise, and they love it just because 'its the 
tube sound'.  Boggles the mind.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Just pick up the phone and give modem connect sounds. "Well you said we should 
get more lines so we don't have voice lines."



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