Hi everyone, following a post I made previously (
http://www.thefretboard.co.uk/discussion/137116/valves-on-their-way-out#latest) I took the advice of
@ICBM and swapped V4 for V1, I also swapped V3 for V2 and that seems to have sorted my issue, with that in mind, I suppose it is likely that v3 and v4 are fine, I also have a few 12ax7s left over from a previous re-valve, can I test them to see which ones are faulty? if so, how would I do that? I'm going to get a new set as I'm not crazy about how these sound but it would be handy to have some known good spares cheers
Comments
No valve testers I know of will do that. They're just checking for performance, continuity, leakage, gas etc. Noise and microphonics are best tested in situ in an amp. Gently tap each valve with a pencil or similar and listen for the result. Volume controls would need to be up a little for any valves prior to them in the circuit, e.g. you won't hear a noisy/microphonic V1 with the channel volume down.
The simplest way is to put it in the amp and listen to it. If you’re familiar with the sound of the amp then a valve with poor gain, bad tone or noise should be obvious - and tapping it should show up microphonics. Trying it in V1 will usually be the most sensitive.
There are almost no preamp valve faults which can damage an amp (unlike with power valves) so this is safe.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Rift Amplification
Brackley, Northamptonshire
www.riftamps.co.uk
As ICBM says, unless a defective valve will damage your amp, then the best test is does is work in the amp.
This is especially true in my experience for microphonic pre-amp valves, especially in high gain amps.
I think as previously stated put the valve under test in the V1 position of a known amp and undertake a tap test.
...just my mind wandering...
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