Sound Devices 664 is a mixer-recorder that comes after the 552 with more functionnalities, more inputs outputs, more tracks.
Sound Devices 664 has 6 mic-line inputs with 12 V and 48 V Phantom, with low-cut and analog limiter, and 2 master outputs, two auxiliary outputs, 6 direct symmetrical outputs. It also has 2 AES3 inputs and AES42, plus 2 'Beta' outputs and 3 camera returns , and up to 8 AES outputs.
Sound Devices 664 also has a communication circuit with internal or external microphone, Ambient Recording-based Timecode generator/reader, and, the icing on the cake, a 24-bit 10 tracks recorder on CF and SD, with a routing table on an LCD screen large enough for a so compact device!
Finally, the optional CL-6 expander allows you to add six faders and a 4 channel LED VU meter, REC and STOP buttons, to use the 6 direct-out connectors of the 664 as line inputs and to add 6 tracks to the recorder taking it up to 16 tracks.