So Sliderbass came up here a few weeks ago to check out my preamp, and brought some killer gear with him - a LDS nEarful, a beautiful Sadowsky and John K custom, - and a DB680. We were finished and were packing up when I realized we hadn't tried the 680... it would have been a lot less expensive for me had I not bothered to try out Frank's unit before he left. This was the first time I had the pleasure of playing though one; they were too pricey for me when they were still in production, and I honestly never paid too much attention to them, because I never thought of them as being well suited for rock tones based on the general reviews and feedback I had seen.
Well, as many of you already know, the DB680 is an extremely versatile piece of equipment, and I was immediately impressed upon plugging in. If you have a good bass and cab, and pair this baby with a good power amp, you are pretty much good to go! My basses are all passive and have SD "hot" P and J pickups, which are pretty high output, and have a strong midrange. They give me pretty much instant rock tone through any amp with a somewhat "flat" voicing. I've found that the DB680 is capable of producing a killer rock tone - I like everything flat with the bright switch engaged. I've also got great results with the low boost in the "+" position, the high mid set to around 1.8kHz, 2 o'clock, and Q at noon, and the low mid set to 180Hz, same other settings as high mid. Plenty of clear grindy, growly tube warmth.
I shot a video the 680 A/B'd with my own preamp for comparison, just to give folks a sort of reference point. With everything set flat on both preamps, I'd say the tone is more similar than different. My preamp has a lot more gain available - in the video, both pre's have the gain set at noon - my pre is dirtier, but not in an obvious way since a lot of it is focused in the midrange. The gain voicing gives my pre a bit of a brighter/edgier/aggressive quality, with thicker mids and low mids. This isn't meant to be a knock on the Aguilar or an advertisement for my preamp - the Aguilar is KILLER - so much so that I actually acquired two of them!
Anyway, here is a quick video comparing both, with all of their EQ flat and gain set at noon. ‪DB680 and JGR comparison.MOV‬‏ - YouTube