From Manufacturer
The CL-6 Input Expander from Sound Devices adds six balanced, line-level inputs to the 664 and 668 Production Mixers. The Input Expander connects to the top or bottom of the mixer and includes six full-sized fader controls, PFL control, and high-pass control. It also features dedicated L and R routing buttons for Inputs 7–12 on the mixer.
The large, backlit Record and Stop buttons provide convenient access to transport functions. Other features include large, daylight-viewable LED meters (with track arm indicators) for tracks L, R, X1, and X2. When the CL-6 is connected, the TA3 connections for Direct Outputs 1–6 on the 664 and 668 convert to balanced line-level inputs. These Inputs are numbered 7–12 respectively. Routing, ISO track arming, and fader control all function identically to the mixer's main inputs.