Hopefully you can figure out what's going on with your codex but if you need a new DAC the D90 is an incredible bargain. I know it seems to rankle some feathers that something that costs $700 can deliver but if you want transparency in a DAC it's hard to better the D90. That's my 2 cents and yes I've heard it and looked at the measurements.
Replace Ayre Codex with Topping D90 DAC
My Ayre Codex takes USB from an ultraRendu and sends balanced analog to an Ayre A7e integrated that drives KEF LS50s. The sound level has become nearly inaudible, and I suspect it's a problem with the Codex -- substituting a microRendu made no difference; the sound level with the Ayre C-5xeMP disc player is fine. Should I send the Codex to Ayre for service or buy a Topping D90? Anyone hear the two DACs?