Microphonic preamp valve? (Video)

[HerbieTheRadDorklift]

Just bought my Einstein 50w from diezel.co.uk.

Super service etc, and I have emailed them this video as the valves are under warranty. They're sending me a couple of preamp valves, so BIG thanks to them!

What do you reckon? How do I see which one it is?

 

[HerbieTheRadDorklift]

Follow up; some amp techy folks have said it's oscillation.

Any word on this being "normal" or how to cure it?

 

[///MK]

Yes it sounds like oscilation and very well may be caused by a bad tube (but a bad tube is not necessarily the cause)

you usually cant tell which valve is micro phonic by looking at it.

The 2 different UN-scientific ways to check

1 replace one valve at a time until the oscillation stops (safest way to do this)
2 if possible tap the tubes slightly with a pencil the bad one will make ungodly noise IME

Again it is very possible the the noise is not caused by a bade tube or even caused by a bad tube that took out a resistor or cap out when it went.
If the easy tube swap does not fix it you relly need to take it to a tech dont take the chance on that fine amp..