The F series from Mesa is the evolution of the Mark series that made the californian brand famous. The closest model to this F30 is the Mark I from which the preamp is derived. The old model didn't offer the ability to switch between its two input and this issue is addressed here with the addition of separate 3 band eqs for each channels. The secret behind the F30's big sound is the inclusion of a fixed curve graphic eq at the end of the preamp. To put it simply, a V curve is always applied to the tone of the amplifier, particularly in the lead "Contour" mode.
The MarkI has always been one of my favourite Mesa models and the F30 does sound very good in clean, crunch or high gain mode, provided you like dipped mids. The depth of the V curve cannot be altered like on the new MkV model and in some instances, it can keep you from cutting through a busy mix: an additional control pot would have been welcome. Nevertheless, the equalisation is well judged so it gives a good compromise. Just be aware that despite its name, this amplifier only puts out about 20 watts!