Test tubes- How to help

I have a Conrad-Johnson PV11A. How can I tell if a tube is blown. It sounds funny and it is very noisy. If the tube is blown, how can I tell which one it is. I don't have a tube tester. the tube compliment is:
V1 & V2: 12AX7
V3 :5751
V4 : 12AU7
V5 & V6 : 12AU7

Only two of the tubes are for the line stage preamp (V5 and V6). The rest are the phono stage. If the noise is on all inputs (and not just phono) it could be one of these two (or both). If so, you should probably replace them both for balance. You may want to consider replacing them all if they all are old.

Is the noise both channels or one?

It never hurts to have a couple extra tubes, so get a pair and see.