How to do tubes up grade in a AR ref 1 preamp?

Wanted to up grade my preamp with all NOS tube but the original tubes was marked from V1 to V8 respectively to coordinate 8 sockets on the board.
After replaced with all NOS tubes, when cranking up the volume there was a distortion on one speaker.
what is the proper way to replace tubes? Anybody could help?
Thank you,
Which tubes have you installed? 
I have replaced all of the 8 tubes with NOS.
It sounds like you have one (or possibly more) bad NOS tubes in that channel.

So, you have (4) 6922's in each channel, just go down the line and switch one set of tubes at a time until you find that the distortion switches to the other speaker. Then you will know which tube is the bad tube, and replace it.
Or replace each tube on the bad side, one at a time with a good original tube. Power off for a few minutes between changes. Keep power amp volume low during power up and down.