I have to say, I sometimes struggle to get a really satisfying tone from a StingRay through an SVT.
I just find it takes a bit more work to get it dialled in without fighting it - which really boils down to how I like to have the 2band EQ StingRay set.
Too much bass boost at the instrument, and the tube in the SVT preamp compresses, acting like a tape bias - you end up with totally out of control woofing lows, mushy mids, painful razor sharp sizzle when you try to brighten things up again.I
I think the key is to be judicious the a 2band EQ, or not veer too far from the centre detents on a 3band EQ, taking advantage of the additional mid-band.
That said, I've got lovely results out of my Marshall, and Sound City tube amps, just utilising their tonestacks - but perhaps a significant contributing factor was that I was not using an Ampeg 8x10 cabinet.
I've also heard people other than myself manage to get great tones out of a StingRay & SVT - here's one of my all time favourites :
2band EQ