I had planned on doing the same thing but with a Mullard Square Getter which is known to be more punchy but no need for one now.
Wig
Wig
Border Patrol DAC tube change
I replace the EZ80 tube in my Border Patrol DAC SE USB+SPDIF with an EZ80 GE made in Great Britain. The tube was made for GE by Mullard. The improvements were significant. The DAC now sounds more dynamic and the high frequencies improved. My wife says its more lively.