I was intrigued by the sound differences between ECC83 tubes of different manufactures, even though on the cathometer they looked about the same, that is why I propose an indirect determination of the vacuum quality in the tubes by measuring anode current at a very low voltage. Worn tubes or with air in them give current values a hundred times higher than normal and smaller differences occur in tubes with different manufacturers, what do you think?
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Valves with air in them affect the getter vapour on the glass inside.
If a valve is gassy, is will flashover at a much lower anode - cathode voltage and have poor thermionic emmission.
This is not what I think, this is a scientificly proven fact.
If a valve is gassy, is will flashover at a much lower anode - cathode voltage and have poor thermionic emmission.
This is not what I think, this is a scientificly proven fact.
It may works, yes - at least to a certain extent : a tube which have a "soft vacuum" often offers a higher current than a "hard vacuum" tube, for the same parameters. Also, it is know since the early years of Radio that a "soft vacuum" is more sensitive than a "hard vacuum" tube, when used as a RF detector.
T
A 12Ax7 Eico tube has a measured anode current of 8nA and an ECC83 Tesla 34nA, clearly the American tube sounds better although the cathometer, gain factor and slope are comparable
