said by Hank:Was there no information that came with the amp from the manufacture that recommended a burn-in period?
Ameritron is silent on the issue.
Some of their advertising still mentions "4 Rugged Ceramic based Russian 572B's".
That was related to the Svetlana / SED tubes they used to use, that I now read were a problem and no longer used by Ameritron.
Well I have 4 Brown Phenolic based unmarked tubes, and a quick call to Ameritron confirms that they are the correct tubes that they now ship with the amp, and there is no 'break in' procedure mentioned.
They do however recommend that I only purchase replacement tubes directly from them in the future.
I have read horror stories about various 'no name', supposedly Chinese manufactured tubes experiencing grid shorts and flash overs, and trying to find a brand new quartet of NOS US made tubes is either extremely expensive, or all out impossible.
I refuse to pay Ameritron double for their tubes, and I never treat any type of power tube as a plug and play device.
I always let new tubes cook-off any internal impurities for a few hours before applying drive, but it sounds like the currently available 572B's are a special case.
The amp runs the tubes at 2900v on standby, and 2500v fully loaded, but it sounds like many 'junk' 572B's are only rated at around 2300v tops, and if that is the case, running the tubes 600v over their maximum rating, it is only a mater of time until there is a catastrophic failure.
Just trying to find someone that has had any experience with these particular tubes, in this particular amp.
I hope I get many long years out of the initial set of tubes, but I want to break them in right, so I don't have any early failure problems.
I may go so far as to change the power supply transformer taps to keep the plate voltage below the norm for the first few months, and if there are no problems, I can gradually step it back up to the full rating.
73