Little old stage rigs from Texas
I have seen a youtube video on BFG's stage rig and basically he has two Marshall Valvestate 120 power amps, one for backup and one for playing. He uses a Marshall JMP1 preamp and a Digitech MEQ mono28 MIDI graphic equalizer in the line then through a Boss SE-70 effects processor with supplied signal from a RJM RG16 MIDI effects loop controller which is fed from a Samson UB-5D wireless system. The Valvestate goes to a Demeter Iso Cabinet with a Eminence Governor that's mic-ed with a Heil PR30 out to the main P.A. and another iso cab with an Eminence Man of War using another Heil PR30 mic which is driven by a Mojave Scorpion to get a stringier tone once again this all mixes out to the main P.A. All that plus some miscellaneous effects pedals are all controlled by his guitar tech Elwood Francis (an excellent guitarist in his own right). The graphic equalizer has presets for all the various guitars BFG has on hand for the performance so they all sound identical as far as their ears can determine. He also had another rig just like it as further backup and according to Elwood has never needed to switch to the backup system since he started tech-ing for him back in 1995.
As far as Dusty is concerned, I bet he has a similar setup. If you look back to the days when ZZ had their equipment onstage both Billy and Dusty had Marshall stacks... a couple of them each. Billy raves about the Bionix Expandora but I don't know if he uses that live. He has stated that he uses one in the studio and on gigs where they don't use their own rigs, like when they use some Orange half stacks as I have seen in a few videos.
Seems that much of the ZZ sound for guitar as well as bass is achieved through a graphic equalizer although if anyone has better info, please chime in.
I will amend and/or correct this blog entry as better information becomes available but for now the ZZ magic tones are not magic, just seems to be plain old common horse sense.