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In the Forum: Melquiades Amplifier
In the Thread: Is it the time to change those tubes?
Post Subject: Rule of ThumbPosted by Paul S on: 7/31/2013
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ZZ, I'm thinking, ramp up the properly-sequenced DC first (and perhaps we go on from here to the earlier-discussed matter of heating and shutdown sequences for each tube...). After that, when I send signal, I start low and ease up on the volume until it "feels right" to open it up, when the system/components begin to express themselves properly. However, I have no idea if/how this protocol affects tube life, per se. I just try to run tubes with the operating points at spec. Like Romy says, some high-spec 6922s, 12AX7s and a few other high-spec small signal tubes might last 10,000 hrs. if they are run at spec. OTOH, some tubes might only last 3 - 6 months before they sour off, like the 6H23s.
In actual practice, if a tube "sounds bad", or if replacing it improves the sound, then it's bad (or sub-optimal) for that application, no matter how it measures. I wrote about my own experience with the Russian 6C33C output tubes that I routinely replaced in that position after 1 year, but I always swapped the outgoing output tubes into a voltage regulator application and got another year out of them that way. I was curious to find out how long some NOS Svetlana 6C33C output tubes would sound good, and I pushed them for 2 years in that position, but I trashed them after that, out of general paranoia. Being "thrifty", I always clean and re-grease tube pins and sockets before I give up on a tube.
Best regards,
Paul SRerurn to Romy the Cat's Site