Have you got a humming valve amp?

[DrNomis_44]

FW, I probably know a bit more about electronics than you, but a lot of this stuff confuses me just as much as it does you, especially when it's being described without the aid of a diagram. So I do my best, propose something based on my empirical testing and then wait for others to expose the errors in my argument. Sometimes being wrong is the only way to learn something. I often find that if you write something incorrect, people will pile in to correct you, whereas if you just ask a question about the same thing, you rarely get more than a few one- or two-line answers.




Doc, probably, though I'd imagine that's for complete catastrophic breakdown (as probably what happened in the noisy valve that started off this thread), which may also be affected by other events (e.g. the two times I ran the amp for a few seconds without a speaker connected). Plus although one manufacturer's 12AX7 should be the same as any other manufacturer's 12AX7 to meet the 12AX7 specification, we know that they can be very different in sound and behaviour. And also there must be significant large manufacturing tolerances, otherwise there would be no need for suppliers to test the valves before making sure they fit into an acceptable category, and no need to specifically match output valve pairs if they were all made exactly the same.

That's very true, most electronic devices and components are made to a certain tolerance, simply because it's impossible to make them exact, in the real-world you don't really need to have components measuring exactly as per their marked values, since most electronic circuits aren't that critical unless they are for specialized applications.


I'm following this thread with a lot of interest.


Servicing a piece of electronic equipment is a lot like trying to solve a mystery, you can regard fault-symptoms as clues as to what may be causing the fault, and by using deductive-reasoning, you can gradually eliminate all the possible causes until you're left with whatever happens to be causing the fault.