Does anyone know the output voltage for the Oppo 970HD? Specifically, I just want to use the two main audio outs playing SACDs directly into a passive preamp that would pass the signal to a power amp. I would need at least 1.0 volts to get sufficient volume since the passive preamp doesn't boost the signal. This is a regularly reported statistic for CD players, but Oppo does not list it in the specifications that came with my player. Thanks.