12AY7 tube is pin-compatible with 12AX7 but with less gain. When used in place of 12AX7, the 12AY7 tube gives a smoother tone that is well suited for Blues and Jazz. 12AY7 tube is used as the first stage tube in Tweed Deluxe 5E3 which is sought after for its bluesy tone.
If you are looking to get the smooth bluesy sound, swapping 12AX7 in V1 with a 12AY7 tube is definitely worth a try.
