Tube filiment voltage ???

[Magnus Danielson]

From: Harry Bissell <harrybissell at prodigy.net>
Subject: Tube filiment voltage ???
Date: Sun, 02 Jan 2000 23:03:40 -0500

>      I remember (well I read that... I'm not THAT old...) that ENIAC
> used a reduced filiment voltage to prolong the life of the tubes so that
> the MTBF would be acceptable.
> Not that the tubes were unreliable... but with that many tubes in one
> place its a done deal that one is (statistically) sure to die at any
> time.
> 
>    Other hand I've heard it said that this was done just to reduce HEAT.
> Thousands of tubes would do that also...

I've heard that in the Swedish BESK they used to overvoltage the tubes every
morning in order to burn out whatever tube that was on the go anyway. This way
they had it fail on demand rather than at some arbitrary point in time when it
was doing calculations. Up-time where expensive things in those times.

> Any audio reasons to give this a try ??? Neat new sounds ??? Waste of
> Time ???

Hmm.... would this mean that the amps would have a "colder" characteristic?

BTW. Is really AC needed or would DC suffice? I've kind of woundered about that
for some time. Sure, AC is practical and just another tap on the transformer,
but you really start to wounder if it is needed for any other purpose. I'm
not well into tubes, so if there where some less obvious reason I'd like to
know.

Cheers,
Magnus