hi mate.......these days i'm sure it's vintage 30's ( sound like crap to me too) it's what dennis Cornell loads his Robin Trower sig amp/cabs, i've always thought it was vint 30's, even before knowing Cornell amps used'em....but over the yrs he's prob tried'em all...the vint 30's handle  bass better than most, and as RT uses the Middle p/up on the strat the most it make's sence really, not only that!! as i understand it he tunes his guitar to D when playin live, again the vint 30's help this!! one of the main factors of his tone is he drives his amps hard without the gain kranked so it's a pretty clean tone, he uses fulltone pedals for extra power...there are clips on youtube with trower and he's pretty open as to what gear he uses...but the main points are, middle p/up, amp pushed hard, vint 30's, big strings, tuned to D when live like the Rockpalast shows on YT...The D tunning could well be due to who he's got on vocals though!!!

rock 'n' roll..

Trower's modern sound is nothing like his Bridge Of Sigh's era tone, so those youtube videos won't guide you there if it's Trowers old tone you're seeking.

There is some good footage from the "Old Gray Whistle Test" television show (UK) of Robin when he still had the old tone (mostly Univibe, pre Flanged-out era) and you can see his 4-input Plexi sitting on top a Fender 2x15 cab loaded with JBL D140F's and there's no mistake, it IS the early Trower tone.
(he did Little bit of Sympathy, and Bridge Of Sighs on the same show)

Although there is no decent shot of his pedal board, he can be seen (and heared) kicking-in a overdrive of some sort for leads, and kicking it back out when he plays rythm/accompanyment. The overdive seems to boost the tone but not really adding fuzz so it's likely it's not a FuzzFace but rather a booster of some kind.

Strangely enough in Trower inteviews he doesn't really recall exactly what his rig was in the early days. He must have been building it as he went along and trying new stuff all the time.

For me it's the old Trower tone that rocks my soul, since about '76 when the Trower Live album and the 1977 King Biscut Flower Hour show recorded at the New Haven Coliseum though (where he did nice version of Daydream) his tone has (IMHO) been getting worse as the years go on. His Fulltone stuff (vibe and OD) doesn't sound anything like his old stuff, and his new amp setup sounds thin and harsh compared to his old sweet singing tone.