Construction
VT = chipboard cab, open-backed,
VTX = Birchply cab, closed-back
Top vents
Because the VTX are closed-back, extra venting was allowed for: -
AD60VT = 1, VTX = 3
AD120VT = 2, VTX = 3
Speakers
VT = 12" 'voiced' Celestions
VTX = 12" Celestion 'Neodog' (based on G12 Celestion Century Vintage*, Neodymium magnets, with a slightly flattened response curve to colour the amp model tones less) (UPDATE May 2011 - originally thought to have 80w speakers based on the G12 Century, it now seems these are 60w speakers albeit very conservatively rated)
Power amp
Basically the same, but the VTX has been 'retuned' to get the best out of the Neodog speakers. In the AD60/120VTH (the heads) this was the only slight modification I'm aware of that was made to later versions.
Controls
Identical except that the VTX have an 8/16 Ohm impedence selector at the rear, to enable easier matching of extension cabs
And that's it!
So, why the changes? The AD60/120VT's are great amps, but tonally Vox had feedback that the VT's started to get flabby and muddy when cranked up at gigs, with insufficient bottom end. Vox listened to the feedback, and the combination of birchply cabinet, Neodog speakers, and a closed back solved these issues. The VTX deliver more volume, greater clarity & tonal range, with much more bottom end.
I have an AD120VTX - trust me, if you're a gigging guitarist, the difference is HUGE. The VTX are a bit rawer and more 'in your face', whereas the VT's (at lower volume) are a little more mellow sounding. The closed-back on the VTX also makes a huge difference to audience projection, but can feel strange 'on stage' as the sound is quieter & quite different when you're 'side-on' to it because more sound/tone is going to your audience than to you as compared to an open-backed rig. But you get used to it very quickly.
Reliability issues have been over-hyped on some sites like Harmony-Central, and the latest VTX are very reliable rigs. There were some reported problems on early VT's (US export models, not UK) where there was a transformer issue (modified for US 110 voltage), but Vox got that sorted fairly promptly. There were also some loose baffles but again Vox got hold of that one too early on.
Rich
