The Flex balanced is balanced in/out. If you'd like to use an unbalanced amplifier (e.g. Powered subwoofer) downstream of the Flex series, here is the recommended TRS to RCA cable to minimize detrimental effect on the audio quality.
Note how the TRS side is only connected with Tip and Sleeve while RCA side is not using the shield.
WARNING: This connectivity work (TRS to RCA) workaround is ONLY to be used for outputs. We've noticed a performance drop on outputs (15dB SINAD drop) for that reason will not recommend customers to use an unbalanced to balanced cable on the "input" side of the Flex. If you want to have unbalanced in/out for both inputs and outputs, it's strongly recommended that you just use the miniDSP Flex unbalanced version. The miniDSP Flex was engineered with best performance in mind and it's therefore our intention to stay consistent on making sure best audio quality is kept for this platform!