I like the amp but it's really bright (I run the bass at 75% and the treble at 20% for a good tone) and with the pre-amp up, it's a bit fizzy and undefined. Could also be the fault of my tubes, they can be pretty old.
they really added a lot of treble to the voicing of the custom classics attempting to make them sound more like beatles recordings that weren't even made using ac15s or ac30s... look into a vintage example (a 30 if you want topboost since vintage ac15s are a totally different preamp that's way gainier) or one of the handwired reissues with fawn tolex and you will be getting a lot closer to the real vox sound and you will be able to use sane tone control settings too (well, sort of, the tone cotrols are highly interactive, for instance turning both all the way down produces a surprisingly nice midrangey sound, turning both up kill almost all bass and gives the classic 60s 12 string sound).... does your ac15 have a 'cut' control? If so you can start turning your treble up and turn the 'cut' up incrementally to remove any harshness and fizz... that's what tis for, kind've a reverse presence so to speak... you may not really want to jack your treble down too low while cranking your bass as it recenters the mids on this circuit
also, try the normal channel, its highly underrated and is a secret weapon that no one likes to talk about
also, the celestion blue is notoriously light on bass, especially when used singley... its a great speaker but may not be to your taste unless paired with a firmer, ceramic speaker like an H30 in a 2x12 configuration
and stop using the master if you are turning the channel volume up unless you are just diling back a tiny bit of level to the power tubes... while the marchless/vox post phase inverter master is a decent circuit, its not great turned too far down and in general is reliant on the quality of your preamp and phase ivnerter tubes.