@wemfan
If you wanna use the Oppo 105 as a preamp surround processor first you will have to set the built-in volume control in the Oppo to variables and make sure you turn down the volume all the way before turning on your Parasound Halo A31 amp. Connect your Oppo directly to your Parasound Halo A31 amp via XLR balanced stereo analog audio on the Oppo 105 to the front LR inputs on the Halo A31 amp, and connect the center channel analog audio out of the Oppo's multi-channel analog audio outputs to a center channel input on your Halo A31 amp. And connect the Oppo's sub out to a subwoofer if you have one. And control the volume from the Oppo.
I assume you are only doing 3.0 or 3.1 since your Parasound Halo A31 amp is a three-channel amp, unless if you are planning to add more power amp(s) to complete 5.1 or 7.1 setup.
Alternatively if you are looking for a very good sounding preamp surround processor (pre pro) and if you don't care for 4K video pass through or Dolby Atmos, DTS-X, etc there are some older preamp processors that I would highly recommend to you and today they can be had at quite reasonable prices due to lack of supports for 4K video pass through HDR, Dolby Atmos, DTS-X, etc.
I highly recommend the Classe SSP 800 av preamp processor. This pre pro originally retailed for $9500 when it was in production and has been discontinued in 2017. Phenomenal sounding AV preamp processor for both movies and stereo music. Nowaday a used SSP 800 can be had in used markets for around $3k ish or less due to lack of supports for latest formats. I used to own the SSP 800 in my reference high end theater room setup.
The Classe Sigma SSP is my other recommendation and again has been discontinued in 2017 and doesn't support latest formats eg 4K, Dolby Atmos, DTS-X etc and nowaday can be had for around $2500 in used markets. The original retail price was $5k when purchased brand new when it was still in production. This is for the original version of the Sigma SSP, not the Sigma SSP Mkii version which retails for $6 brand new when it was in production and the Mkii version has also been discontinued. The Sigma SSP Mkii version supports Dolby Atmos, DTS-X & 4K video pass through but not HDR nor Dolby Vision.
Both the Classe SSP 800 & Sigma SSP would sound excellent.
If you go a pre pro route, you will have to connect your Oppo, cable TV box, etc using HDMI to the pre pro. Your Oppo 105 has dual HDMI outputs, one optimized for audio and the other for video. You will have to split the HDMI AV outputs in the Oppo's menu and connect the video only HDMI out directly to your TV and the audio only HDMI out to a pre pro.
Hope this helps.
If you wanna use the Oppo 105 as a preamp surround processor first you will have to set the built-in volume control in the Oppo to variables and make sure you turn down the volume all the way before turning on your Parasound Halo A31 amp. Connect your Oppo directly to your Parasound Halo A31 amp via XLR balanced stereo analog audio on the Oppo 105 to the front LR inputs on the Halo A31 amp, and connect the center channel analog audio out of the Oppo's multi-channel analog audio outputs to a center channel input on your Halo A31 amp. And connect the Oppo's sub out to a subwoofer if you have one. And control the volume from the Oppo.
I assume you are only doing 3.0 or 3.1 since your Parasound Halo A31 amp is a three-channel amp, unless if you are planning to add more power amp(s) to complete 5.1 or 7.1 setup.
Alternatively if you are looking for a very good sounding preamp surround processor (pre pro) and if you don't care for 4K video pass through or Dolby Atmos, DTS-X, etc there are some older preamp processors that I would highly recommend to you and today they can be had at quite reasonable prices due to lack of supports for 4K video pass through HDR, Dolby Atmos, DTS-X, etc.
I highly recommend the Classe SSP 800 av preamp processor. This pre pro originally retailed for $9500 when it was in production and has been discontinued in 2017. Phenomenal sounding AV preamp processor for both movies and stereo music. Nowaday a used SSP 800 can be had in used markets for around $3k ish or less due to lack of supports for latest formats. I used to own the SSP 800 in my reference high end theater room setup.
The Classe Sigma SSP is my other recommendation and again has been discontinued in 2017 and doesn't support latest formats eg 4K, Dolby Atmos, DTS-X etc and nowaday can be had for around $2500 in used markets. The original retail price was $5k when purchased brand new when it was still in production. This is for the original version of the Sigma SSP, not the Sigma SSP Mkii version which retails for $6 brand new when it was in production and the Mkii version has also been discontinued. The Sigma SSP Mkii version supports Dolby Atmos, DTS-X & 4K video pass through but not HDR nor Dolby Vision.
Both the Classe SSP 800 & Sigma SSP would sound excellent.
If you go a pre pro route, you will have to connect your Oppo, cable TV box, etc using HDMI to the pre pro. Your Oppo 105 has dual HDMI outputs, one optimized for audio and the other for video. You will have to split the HDMI AV outputs in the Oppo's menu and connect the video only HDMI out directly to your TV and the audio only HDMI out to a pre pro.
Hope this helps.