What are you using for a preamp? If you have an outboard preamp with inserts, you use 2 TRS to TRS cables as inserts (send and receive). If it doesn't, you use the unbalanced outs with TS to TS cables, and then 2 TS to TS cables to the 1/4" ins on your 1680, which will accept the unbalanced signal via TS plugs just fine, with about a 3 dB loss in gain. If you're using the pres in the 1680, check the manual under "using outboard effects" which will explain how to use 2 of the 1/4" jacks as aux send/receive. At least that's how it works on my 1824, and I'm betting it's about the same on your machine. Frankly, I prefer #1, especially with a DBX386. That way, not only is the signal compressed before it ever hits the board, but also, you gain the benefit of the DBX's superior A-D converter. Hope this helps- Richie