Question How to calibrate the main outputs to 0dB for K-14 Answer The max. output on Impact Twin is 12dBu = 3.08 volts.  Based on the K-14 reference of 0 VU = 85 dB SPL, generate a 1 kHz test tone at -14dBfs from your audio software, adjust Impact twin's output level encoder to read 0.7746 volt on a DMM (volt meter).