Glad this is finally getting looked at before my 30-day return window runs out. I have five days left know whether this problem will be fixed by VOX or a work-around identified.
Before commenting on your questions posed above, I have found the problem does NOT exist when using headphones, so it would seem to be the issue is downstream in the interaction between the modelling/preamp sections and the power amp section.
1. doesn't matter if 2 patches are saved at same volume, or switching manually between models using the controls is there and invasive ... the higher the gain on the model the more invasive. It pops above the band mix (drummer, bass, keys ...etc). Even on lower gain channels (e.g. switch between boutique clean and modded clean) there is a volume surge but not as intrusive.
The problem is extremely easy to replicate -- set the back-of-amp watts output at 50%, 3/4 on volume, gain and master and hit a D chord (or whatever) on AC30BM then while it is sounding, switch modelling dial to the right UK 80's and BAM volume surge for a quick moment then back to normal -- just long enough to be incredibly disruptive and annoying.
My serial number is in the 3,000's, the VT50 at my retailer is S/N around 1,500 and has the same problem on their floor model.
2. It still surges at full power watts (I normally have it about 60%) although not sure if it is a volumne surge or just increased distorition at that volume level it is so loud already
3. don't know
4. the volume spikes definitely vary depending which amps / models are being selected, some seem to have no spike at all, some moderate, and some massively annoying
I REALLY REALLY hope this gets fixed -- hard to believe they released a product with this kind of issue and otherwise it is a fantastic product but I can't live with it and it will go back to the store for refund on day #30 if not fixed and I will have to buy another brand ... I am sure that VOX will have the same problem with any customer using this amp to play live or in a band or recording situation.