No Bass with 5-Channel Analog Inputs

I am using the 5.1 analog outputs out my Oppo UDP-205 to connect to a very-old Yamaha RX-V995 that was produced way before HDMI. I'm doing this to take advantage of the superior DAC in the OPPO. I can't seem to get any bass out of the system this way. Using the exterior DAC nullifies all adjustment on the Yamaha. I have all speakers set to "small" in the Oppo's speaker set-up, and I have tried adjusting the cross-over as well. I get plenty of bass when I bypass the OPPO when watching TV. My OPPO BDP-95 did the same thing when I connected it this way. I used to be able to rattle windows when connecting disc spinners through the 2-channel inputs. Does anyone have any ideas on other settings I can adjust on the Oppo to get more bass?

Do you have subwoofer(s) connected to the Yamaha? 

If not, you need to set the Oppo to have all the main speakers as Large and "no sub."

Yes, I have the Subwoofer connected to the Yamaha with bass setting set to "Both" so that my Mains and Sub share Bass frequencies.

I see that some Receivers have feature to allow for +dbs boost for Subwoofer when using analog inputs.  Unfortunately, mine does not.
Since your Yamaha " nullifies all adjustment," I would focus on the Oppo to first make sure that you are getting signals from all the output channels. 
(1) Does the FR/FL channels change/respond at all to changes in the Oppo of level and/or crossover for BM?
(2) With careful manipulation of the volume control on the Yamaha, connect the .1 output of the Oppo to the FR/FL input of the Yamaha and determine if there is a signal and/or if that signal is affected by changes (in the Oppo) of level and/or crossover for BM?
Yes the FR/FL do respond to large/small speaker selection in the Oppo.

I think I follow what you are suggesting here.  The Receiver may not be receiving/ processing the (.1) subwoofer signal?  I know it is not the Oppo since it has done the same thing with two different Oppo's.

I will pull interconnects the first chance I get.  Thanks!