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Re: Preconditioning S-30

Posted by Al Sekela (A) on January 20, 2003 at 19:34:53

In Reply to: Preconditioning S-30 posted by Steve on January 20, 2003 at 19:23:36:

Steve,

Congratulations on your new amp.

If the 6AS7 tubes have not seen B+, the recommended procedure is to run them with the filaments only powered for 48 hours before turning on the B+. This appears to stabilize them and cuts down on the infant mortality rate. No signal source or loudspeakers are needed for the preconditioning procedure. In fact, you could make a simple tube cooker from a filament transformer and a few sockets, to permit off-line preconditioning of spare tubes for future use.

Keep in mind that tubes in general, and these tubes in particular, were and are made in factory conditions that predate the modern levels of cleanliness maintained in semiconductor factories. Absolute levels of quality and reliability of tubes are appalling compared to those required for successful semiconductor manufacturing. We are in one sense fortunate that this preconditioning procedure works as well as it does. It saves us a lot of testing and balancing with a new batch of tubes.

-Al

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