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Questions about tubes and gear that glows. FAQ

RE: Do matched quads become "unmatched" when they age?

I would say yes. As soon as a tube is fired up - it starts to age and with that can come a change in current draw and transconductance. Now if a "matched" quad is all running the same parameters within that amp, they theoretically will age and change values somewhat evenly. How precise or imprecise the actual component tolerences are within that amp are, will determine even or uneven wear. You can have a "matched" quad of tubes within 1% or less of each other, but if the design and components of the amp use a 20% slop (my term) factor, getting even readings might be a bit tough, unless each tube has an individual bias pot - then things get much easier.
I've tried to word this rant carefully, but if I'm way off, go ahead and flame away!
Over the last few years and looking at many schematics and the huge concern about matching, there's a lot of variables in our systems that can cause a lot of time being wasted searching for something when it might not be attainable.

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