On 7/14/06, Andrew Lentvorski <[EMAIL PROTECTED]> wrote:
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
> ...
Possibly I have been aware of vacuum tube technology longer than both
of you put together. At least since 1952, when I decided that it
would be a good thing to learn, and spent a couple of months reading
_all_ of the back issues of Electronics Magazine from its founding in
the early 1930's up to date.
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.
Distortion in a single-ended overdriven tube amplifier would be more
even harmonics. Cancelled by push-pull. Greatly reduced by applying
negative feedback, developed at Bell Labs in the late 1920's. <
http://www.invent.org/Hall_Of_Fame/16.html >
> 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 ...
Why hum as the TV warms up? Doesn't seem to be characteristic of
vacuum tubes, but perhaps of poorly designed (to minimize cost)
circuits.
Super-regenerative amplifers went out some time in the 1920's except
for experiments by radio amateurs and the like. As the cost of a
single vacuum tube was driven down by mass production, the necessity
of multiplexing several circuits through one tube decreased. To a
great extent, the increased production was due to the development of
tubes with 6.3V heaters to be used in car radios.
carl
--
carl lowenstein marine physical lab u.c. san diego
[EMAIL PROTECTED]
--
[email protected]
http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
