A Stupid Idea
On Apr 18, 11:08*pm, John Byrns wrote:
In article
,
*Bret L wrote:
*The latest AudioXPress has on its cover a stereo amplifier using one
4D32 tetrode in Class AB2 per channel as an output device.
*Why do people persist in acts that aren't just stupid but willfully
destructive?
*The 4D32 was neither designed for nor is it really any good as an
audio amplifier. Its only use today is as an RF output tube for the
beautifully built Collins V-line transmitters and a few military field
transmitters. The supply of these tubes is limited and it is doubtful
any more will ever be made. No really good substitute exists, although
the set can be kluged to operate at reduced power and efficiency with
the VHF twin triodes paralleled together.
*Yet we have self centered and ****ish audiophools who persist.
*Can you see why I get mad? If the 4D32 were a fantastic audio tube,
I'd say go ahead and use them up. Make them make more. But it is in
fact terrible. It sucks as an audio tube.
*Even an 811 is far better. Rein Narma made them work just fine.
Hi Bret,
Do you have any idea how audioXpress was able to build an amplifier
using only a single tetrode per channel operating in class AB2? *Class
A2 I can understand, but class AB2 only works for audio in push-pull
circuits. *If these people have actually built a class AB2 SE amplifier
they certainly aren't audiophiles!
Busted. I meant to say Class A2.
On the other hand it isn't obvious why you say that the 8D32 isn't
"really any good as an audio amplifier"? *It looks OK to me, certainly
better than a 811, and it has some interesting characteristics, I may
have to try a design with it, although I would probably go for the 8D22
variation, so you can rest easy.
Its plate curves are humpty as hell: it isn't linear. It is just
pretty inconveniently configured for its plate rating in terms of
screen requirements, and there is good reason why Collins eschewed it
even for audio (the modulators used 810s for this power range
typically.)
It isn't common or cheap either.
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