External DAC For Oppo 105 At What Cost?

I use a 105 as a transport and output everything over HDMI into my Bryston DAC3.  All High Rez silver discs and downloads play at native resolution, and the Oppo outputs DSD from SACD over HDMI.  That would be my advice on getting the best from your Oppo

I had the same issue with my 105. Strongly suggest you NOT modify it, but find the right DAC. It is not hard to outperform the DAC in the 105. I use an LKS that beats the 105 by a mile, but it’s not for everyone. If you decide to sell a modded 105, you will never recover anything like the cost. If you buy a good DAC it will give you many more options as your digital universe opens. I’ve moved way past the 105 using it now for video and for ripping SACDs.

As for which DAC, that is such an open question that there is no right answer for everyone and every system.  You'll have to do your homework.  Two people will compare two DACs on different systems.  One will hear no difference; the other will hear a great difference.

I don’t know why folks on this board are so resistant, but the best SQ (as well as ease of playing) is gotten by getting rid of "players" and ripping silver disks.and sending the files directly to the DACs. The silver disks add nothing, only detract.

670 bucks for a Denafrips Ares will do it. outperform the internal dac in the 105 player.

Just to hear the difference, I tried an old PS Audio Digilink III with my Oppo 105, and it added something sometimes to some tracks and the filters were kinda fun to play with.  Then went on to their Perfect Wave DAC which was significantly better, then added the bridge allowing straight ethernet based feed from Tidal etc as well as NAS and stopped spinning discs.  Never got around to ripping them either, and Oppo now resides in second system.  

But I am very curious to hear a DAC with tubes in the outboard stage - iFi, the Modwright Oppo, and now PrimaLuna, probably others out there.

Bottom line, as mentioned by melm, get a good DAC with all the input options and your digital universe opens up big time with much better SQ.