That doesn't seem correct. I suggest you set the level of the 105 for one of the channels that doesn't go through the preamp to 75 dB SPL, using a sound level meter. Without changing the level of the 105, set the level of the preamp for a channel that does go through the preamp to also be 75 dB SPL. Mark that level on the preamp as unity gain. For 7.1 HT, use the level (volume) control of the 105; for non-105 sourced stereo, use the level control of the preamp, but don't forget to reset it back to the mark for HT.
You may want to set SACD output in the 105 menu to be PCM, so speaker distances and crossover are active for multichannel music.
I use the procedure outlined above in a setup in which analog stereo from an Oppo 105, a Sony XA5400ES, and a Parasound JC-3 phono stage go through a JC-2 analog stereo preamp; surround channels from the 105 go directly to amps and SW to a bass manager for a pair of subs.
It's easy and the sound, whether stereo or multichannel, is superb.
db
You may want to set SACD output in the 105 menu to be PCM, so speaker distances and crossover are active for multichannel music.
I use the procedure outlined above in a setup in which analog stereo from an Oppo 105, a Sony XA5400ES, and a Parasound JC-3 phono stage go through a JC-2 analog stereo preamp; surround channels from the 105 go directly to amps and SW to a bass manager for a pair of subs.
It's easy and the sound, whether stereo or multichannel, is superb.
db