Outboard reverb. I finally caved on this. Loved the EH Holy Grail sound, but not the noise. Short on bucks, so couldn't do Uncle Spot. Found a mint Fender RI Reverb tank, with upgraded power tube installed. I've got a few more mods to make (NOS preamp tubes, maybe changed caps), but already I can say WOWEE. In combination with my Gibson GA40, remarkable. That amp has a smokey, howling sound. The reverb adds a touch of gain and bite. Amazing sustain, some real sting with my G&L ASAT Classic. I'm not happy to have something additional to lug around, but really happy with this sound.