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?
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@furiouslyadrift is that an Audio Science Review verdict or just your own 2 cents? If that is your 2 cents fair enough, if it is courtesy of the ASR crew then it is a measurements verdict, nothing to do with the sound.
I set the Codex input to USB and output to DAC, but no audio.  I'll check cabling for the ultraRendu setup.  I may have screwed that up after I substituted the microRendu when trying to find the fault.
I’m in the “any distortion is just noise” camp. For DAC chips, I tend to favor AKM for their VelvetSound profile (no ESS distortion hump) and the AK4499 truly is an excellent implantation. It’s AKMs first current drive chip and it’s a huge step up. It’s also a pain to implement into a functional DAC. They really nailed it with this chip. 
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.