Re: "Burning - in" Double Triodes
'Burning In'
* To remove the mortal infants (weed out the early failures badly made).
* To stabilise characteristics. I have seen Mullard data which gives design ratings for characteristics for maximum cathode current, with a footnote that for a new valve a higher rating might apply. (TV timebase output valves). So a designer making a trial circuit would use a valve well 'burned-in' not a new one from Stores.
* Other components - electrolytic capacitors are well-known to deteriorate in storage. A period of time to re-form can be necessary before full performance is regained. We wouldn't call it burn-in, but as it is the same process of putting power on and waiting, then yes it can and does make a difference!
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