it should be vox like, its just a 50s cathode follower tonestack preceeded by a triode stage... which is what a top boost really is - not so different from a tweed bassman, plexi or laney supergroup apart from some caps and resistors for voicing that 1st triode stage, a midrange pot and like 1 resistor value and placement in the actual tonestack... lookat a Gibson GA77, 70 or any of the treb/bass tweed fenders like the pro and you'll find they are virtually the same as the top boost circuit, the Gibson is even voiced damned similar from input thru 1st stage, there's 1 part's difference and its not the value but the implementation, I think Dick Denny lifted the schematic from the GA77 but got it wrong (or he reverse engineered one and made an error or the amp he used was built wrong, quite common in early Gibsons) when Vox decided to add tone controls to the ac30 brilliant channel... Vox definitely referenced Gibson amps a lot. The AC15 is very similar in conception to the GA40 Les Paul model, especially the 2nd series on with the 5879 mini-pentode as V1 and the weird-ass (but awesome) seth lover vibrato circuit on channel 2. No negative feedback, the weird-ass tone control wired into the phase inverter, long-tailed-pair phase inverter in a small amp that Gibson and Fender would typically have used the cathodyne or paraphase PI configurations, channels mixed directly at the PI... but yeah, look at the big 6L6 Gibsons from 55 to about 61 and you will see a proto top boost ad these amps usually have a non-tonestack channel too. The pro/super/bandmasters are similar but the 2 channels just have slightly different voicing and the 2nd gain stage that drives the tonestack before the cathode follower doubles as a simple tube mixer. But all these amps are awfully similar. A tweed deluxe has a lot in common with the ac30 too. Cathode bias, no negative feedback, low power filtering, small tube rectifier, but the front end is basically the same as the bigger tweeds but with a shared 1 knob tonestack that is effectively a set of variable bright caps and variable deep caps on either side of a pot, pretty much everything smaller than the Bassman even got the cathodyne or the superprimitive para phase inverter.... but I could go on and on. If you like tweed fenders and vox ac30s you will like any 2 gain stage cathode follower setup with a 2 band tonestack...
EDIT:
hell the hotrod deluxe, blues jr? all have this arrangement and are only a couple parts difference from an ac30 preamp. One could mod their blues jr you be a top boosted ac15 quite easily if they so desired. Disconnect the mid knob, change a few caps and resistors, change the way the bass pot is wired to the treble pot and ground and then change the bias scheme from fixed to cathode bias, probably need to adjust some resistor values to get the low voltage/high current configuration for the el84s vox used.... then you lift the negative feedback loop and voila... you could do something similar with a hot rod deluxe too I'll bet making a mutant hybrid design with American tubes run british style.... it'd have some attributes of Neil Young's 6L6 5E3 and some attributes of the ac30 and bigger fenders.... but since they are all PCB amps I wouldn't recommend trying. You will probably just burn some traces up.
