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From: john larkin <JL@gct.com>
Newsgroups: sci.electronics.design
Subject: Re: big L
Date: Sun, 22 Dec 2024 08:03:06 -0800
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On Sun, 22 Dec 2024 09:08:35 -0500, legg <legg@nospam.magma.ca> wrote:

>On Sat, 21 Dec 2024 22:01:36 +0000, liz@poppyrecords.invalid.invalid
>(Liz Tuddenham) wrote:
>
>>Cursitor Doom <cd@notformail.com> wrote:
>>
>>> On Sat, 21 Dec 2024 11:35:54 -0800, john larkin <JL@gct.com> wrote:
>>> 
>>> >On Sat, 21 Dec 2024 16:53:07 +0000, Cursitor Doom <cd@notformail.com>
>>> >wrote:
>>> >
>>> >>On Sat, 21 Dec 2024 11:16:18 -0500, legg <legg@nospam.magma.ca> wrote:
>>> >>
>>> >>>On Tue, 17 Dec 2024 06:58:32 -0800, john larkin <JL@gct.com> wrote:
>>> >>>
>>> >>>>What's the biggest inductor, the most Henries, that you know of? I
>>> >>>>seem to recall some audio transformer that was something like 100 H.
>>> >>>
>>> >>>The SAFT/Alcatel plant in Scarborough used to have 
>>> >>>largish inductors for loading. Air-cored - ~10ft 
>>> >>>on a side.
>>> >>>
>>> >>>Your watch would stop, if you were too close.
>>> >>>
>>> >>>Large L ? Who needs it?
>>> >>
>>> >>In the olde days we used to have audio output transformers  for
>>> >>impedance matching purposes, but modern amps don't seem to need 'em.
>>> >
>>> >And long ago tubes were expensive so it made sense to get voltage gain
>>> >from interstage transformers.
>>> 
>>> Indeed. And that's just one aspect of it. The designers in the early
>>> stage of toob development deserve huge respect for the performance
>>> they were able to wring out of a single stage - and all just to save
>>> the hard-pressed consumer back in the day a few sheckles.
>>
>>Have a look at:
>><http://www.poppyrecords.co.uk/httpdocs/other/AMC5.pdf>
>>as an example of incredibly efficient design.  It took the output from a
>>ribbon mic and raised it to 0dBm line level.  By using a mixture of
>>current and voltage feedback, it terminated the mic correctly without
>>the need for a terminating resistor, which would have wasted signal
>>power and generated Johnson noise.
>
>link not valid from here . . . .
>
>I only ever did commercially impractical valve circuits. Often 
>using one-off components that couldn't be replaced without 
>major toil.
>
>One way of separating the hobby from work.
>
>RL

When I was in high schoolI worked summers in a physics lab at a
university.

I designed a radiation counter, for class use, with tubes. It used six
of the cool dekatron gas-filled tubes that were decade dividers and
displays in one bulb.

https://en.wikipedia.org/wiki/Dekatron

Neon bulbs could be fun.

https://upload.wikimedia.org/wikipedia/commons/f/f7/Dekatron.gif

And I designed  and built a high-voltage square wave generator with a
half-bridge of two giant transmitting tubes, for Stark effect
microwave spectroscopy.