They should give you a new one, as far as I know it shouldn't do that. You paid for a quality product, they should give you one. This is sad because this amp is on the top of my wish list .

Any one else has this problem with their cubs?

Valves do go bad quickly on occasion - sometimes right out the box. How old is it and where did you buy it from? There is usually a three month warrantee on valves, so if it's a new amp, they should replace the faulty valve (at the distributor's expense, so it's no skin off the store's nose).

What you have is a microphonic valve. To identify the culprit tap each one with a pencil or pen until you find the one that rings. If it's one of the three 12AX7s, simply pull the old one and replace. If it's one of the EL84 power valves, both will need replacing with a matched pair - but no other biasing or anything is needed, so you can do it yourself.

Thanks

I bought it last year December. I just got the feeling that either the shop or the supplier doesn't want to help.

I'll check out the valves as you discribed, I hope thats the problem.