On a Blackface or Silverface Fender, V1 is the farthest to the right looking at the back of the amp. HOWEVER, V1 is the first gain stage for the NORMAL channel. If you don't plug into NORMAL, don't waste a good tube here. As a matter of fact, you can leave the tube out altogether and get a little more gain out the VIBRATO channel. If you use the VIBRATO channel, the second tube from the right (V2) is its gain stage. If you use reverb or vibrato, put your good tube here!