I am using a pair of Tung Sol EL34B for a guitar amp push-pull output stage, and I have come across the following: Tung Sol specifies that the limiting value for G2 voltage is 425V.
In my application, cathodes are at 0V (fixed bias), and since B+ is around 456V, the Vg2 voltages rest at 453V. Which exceeds the ratings of the manufacturer.
The bias voltage is around -40V, resulting in about 35 mA current per tube (the actual currents are 20% apart, which I think is acceptable for matching.)
Is this voltage stress really a problem? The amp has operated for about 330 hours without any noticeable changes in behaviour or problems.
In my application, cathodes are at 0V (fixed bias), and since B+ is around 456V, the Vg2 voltages rest at 453V. Which exceeds the ratings of the manufacturer.
The bias voltage is around -40V, resulting in about 35 mA current per tube (the actual currents are 20% apart, which I think is acceptable for matching.)
Is this voltage stress really a problem? The amp has operated for about 330 hours without any noticeable changes in behaviour or problems.
Phillips and mullard allows 500V ( https://frank.pocnet.net/sheets/010/e/EL34.pdf )
telefunken and JJ 450V I would not worry about your tubes, if they manage they do. You will eventually replace them later as tubes are consumables.
telefunken and JJ 450V I would not worry about your tubes, if they manage they do. You will eventually replace them later as tubes are consumables.
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