I’ve never worked a gig in TV audio where a Q box hasn’t been used.  I’ve used it to test lines, check mics, calibrate consoles, an intercom, an in ear monitor amplifier for a drummer who forgot his mackie power supply at home (drummers….)

Seriously valuable tool.

Should land you around $200 and that’s a steal
http://www.bhphotovideo.com/c/product/279655-REG/Whirlwind_QBOX_QBOX_Audio_Line.html