kelsey hudson wrote:
It seems as though tubes aren't really taught at all anymore -- old
technology? What about the subtle nuances that made tubes great? Those
second- and fourth-order harmonics that give the sound beauty and warmth
...
Second and fourth? I thought it was the even harmonics that the old
school audiophiles hated and the odd ones that they liked. However, it
has been so long since I used a tube that I can't remember the
configurations used for amplification. Consequently, I can't even
derive what the distortion harmonics would be.
Electron tubes are something I wish would gain in popularity once again.
It's sad that something so revolutionary and so neat gets passed up
because it's too big and too difficult (read: expensive) to manufacture.
Scientists still aren't able to duplicate their effects in silicon (and
you EE people -- don't even get me started on MOSFETs. They don't sound
the same! :D)
<snicker>
If you want electron tubes, you probably have to look at MEMS. You can
create emitters and plates in silicon if you etch it right.
Gone are the days of diode, triode, pentode, getters, heaters, plates...
Most of you probably only saw tubes in your grandparents' ancient radios
or (god forbid) their 1950-era black and white televisions (still
working, I might add -- says something about the quality of today's
electronics).
Um, yeah. And the hum as the TV warms up. The occasional maximum
volume screech as the superregenerative amp goes into overload before
the reset circuit hits. And I can go on and on ...
But, we're supposed to forgive our elders their myopia about the past.
;)
One thing most people probably don't know: tubes are still used in some
places today because they're capable of a lot more power output than
silicon. Almost all commercial radio stations utilize large electron
tubes for the final drive stage in the RF amplifiers. Reason?
Because they already bought all the tube equipment and capital outlays
for radio stations are foolish until something dies.
Transistors (or arrays thereof) which can handle between 35,000 and
100,000 watts of output just don't exist. It's more cost-effective and
smaller (believe it or not) to manufacture a large tube to do it
instead.
I was about to swat you about how many stations actually operate at
those powers, but, wouldn't ya know, the first station I grabbed:
"That 94.1 facility is a grandfathered superpower 100 kW class B"
Some nice pictures of transmitter towers and support in San Diego:
http://www.fybush.com/site-030320.html
However, IIRC, the vast majority of TV transmitters are actually 20kW
and below with the rest of the gain coming from the antenna. MOSFET's
seem to be able to handle that range just fine.
-a
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