Don't have one brand for you to try, but these tubes are not expensive in the world of high end audio. Check a place like Triode Electronics in Chicago (great source for tubes & related parts.) For about $200 you could buy a pair of every 12AU7 they offer (8 pair).
To replace tubes, just turn the equipment off and give it 10 or 15 minutes for the tubes to cool completely. Pull the old tubes out of their sockets (gently with not too much rocking) and then insert the replacement. The tubes can only be inserted in one orientation, so look carefully at the alignment. Replace the cover, fire things up and listen!
To replace tubes, just turn the equipment off and give it 10 or 15 minutes for the tubes to cool completely. Pull the old tubes out of their sockets (gently with not too much rocking) and then insert the replacement. The tubes can only be inserted in one orientation, so look carefully at the alignment. Replace the cover, fire things up and listen!