Noises coming from inside the tube

[Sh7eleven]

I just received a NOS tung-sol 5998 for use in the crack and I'm hearing occasional pangs emanating from inside the tube. I've powered it up twice - I heard the sounds on the last power down and the most recent power up. (Wasn't paying too close attention on the first power up) The Sounds are similar to those you might hear when you turn your car off and the engine is cooling down.  They have seemed to stop after about 5-10 minutes. The pangs produce no noise into the headphones and the tube sounds great.

Is this normal for a tube warming up or cooling down? Will this normally go away or should I return the tube.  I've not heard this kind of noise from any other tube I've used (not too experienced though.) 

[Jim R.]

No problem -- this is normal for some tubes -- just expansion and contraction as things heat up or cool down.

-- Jim

[Sh7eleven]

awesome - that's what i figured when I didn't hear anything in the phones and the tube was pretty silent. I bought from a dealer on a recommendation from a member here so I wasn't too worried but I have ten days to return the tube so I thought I best consult the experts while I still can.   

[Paul Birkeland]

If you are ever around a 6C33B amp, have the owner shut it down for you.  Those beasts can ping and creak for 10+ minutes as they cool down!