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tubes 6082 Raytheon

Posted by sprussog on May 8, 2020 at 11:16:08:

Hello dear people, I built the Macovski OTL. The power supply is more modern and I built a reliable speaker protection. A small hum is annoying me, for which I cannot find the cause. For all tubes i have a DC heather.
The preamp power supply is separate from the end stage power supply. I installed another preamp stage ( JJ828 ), the hum became less. Is it the many different tensions in the preamp stage that cause this?
Lots of 6082 tubes have been broken lately. They are now 53 years old, NOS, in best quality. Thats normal for this Raytheon tubes? Sometimes I can see some rust on the bases. Best greetings from Steffen