Tube Rolling - Any tips or caveats

My first experience with NOS tubes has not been great.

For simplicity reasons, I started out by swapping my input tubes on my power-amps (Quicksilver Mid-Monos) with the pair of Telefunken 12ax7s. It sounded great, it tighten the bass and added definition to the imaging of the individdual instruments within the sound stage.

During my second listening session, less than 4hours total I lost the left channel. I let things cool down for a few hours swapped back the old tubes and voila! We were back up and running. Clearly a faulty not so New NOS tube.

Luckily the audio shop agreed to exchange it.

"Would upgrading the input tubes (12ax7) of the power amps provide a bigger improvement (in terms of dynamics) than upgrading the phono stage of the pre?”

Nick sr, I think that’s almost impossible to determine in advance. I can tell you that the potential for improvement by changing the 12ax7s can be huge. Call a reputable pro who guarantees satisfaction with a credit/swap policy. I’ve been most satisfied with Andy at "Vintage Tube Services" and Brent Jessee. Both stand behind their tubes and offer excellent advise. I can’t imagine your regretting the calls.

FWIW, I bought my 12ax7s from Brent Jessee.

http://vintagetubeservices.com/

http://www.audiotubes.com/12ax7.htm

I brought the Tele's back to the store and they tested them, and they tested fine(?) 1100 microhms.

Regardless they exchanged them without question, so I took a pair of PSVANE 12AX7-Ts, plus some cash back.

Is this normal that a tube could test well and then be none functional when installed in the amp?

Phaelon, I checked the VTS site, it is fully very interesting information. It seems that the Tele's I had may have come from VTS as they were marked with a little red spot of paint on the top of the tube.

I am rollin' on. I will be listening to the PSvanes this weekend in the power amps.