When Alex Brinkman at Ayre, who has been an extremely patient person, first asked me to review the Codex, it was not in the context of Codex as a combined high-resolution DAC with both USB and TOSLINK inputs plus a headphone amplifier, but pretty much as a direct comparison, USB DAC only, to my Ayre QB-9 DSD, that I use in desktop system with an iMac, Audirvana Plus, an AudioQuest Diamond USB cable, Stealth Sakra interconnects (both balanced and single ended) going into a Cavalli Liquid Gold and Woo WA5-LE V2 with Western Electric 300Bs respectively. The QB-9 DSD, though much more fun and rich in the bass than earlier versions of the QB-9. In the context of that desktop, headphones-only system, it’s still just the right thing even though the Codex is inherently darker and more three-dimensional than the QB-9 DSD. What I did fine is that Codex did much better with music servers, such as the Aurender N100H, and with ever better USB cables, my personal favorite being the entry-level Stealth ribbon USB cable.
In fact, I’ve already told Alex that I want to buy the Codex, not to replace the QB-9 DSD, but to use in a third system I have with the Aurender N100H, the Stealth entry-level USB cable, and the Codex, feeding the all-tube Triode Audio Corporation TRV-88SE, a push-pull amplifier using four KT88’s, via Audio Note AN-Vx interconnects terminated with Eichmann Silver Bullet Plugs. The TRV-88SE, then runs through bi-wired Audio Note Lexus (copper) speaker cables into Audio Note AX-Twos with internal copper wiring replaced with silver, and attached to tall steel, dry sand filled stands with a few strips of Blu-tak. The net result is wonderful, about as analog sounding as you could get from a digital source going into a great tube integrated amp and possibly the most perfect pair of bookshelf monitors ever designed and made, kind of like Spendor Preludes but better or perhaps a pair of LS3/5a’s with bass, amplitude, and dynamic range (plus about four times bigger).
One album I’ve listed to a lot on this little system is the eponymous David Bowie often known as Space Oddity. It’s a recent release at 24/192, but the Codex doesn’t so much process it as it plays it, almost like a Koetsu Rosewood Signature carefully slipping through the grooves of an original pressing on a not-so-entry-level turntable. I picked a Koetsu specifically because it has a combination of warmth and clarity, with no loss of high-frequency detail, but mostly you can listen with it effortlessly and never feel like you’re missing a thing. In that same sense, I can listen to the N100H / Codex combination indefinitely. I’m not saying you couldn’t drop the Codex in place of the QB-9 DSD attached to an iMac, but I would be cautious, because they are mostly twin sons of different mothers, each with its own strengths and weaknesses. The QB-9 DSD is tonally more neutral but less dynamic whereas the Codex sounds rich and warm to me with plenty of dynamics, but the QB-9 DSD seem to favor computers whereas, for whatever reason, the Codex seems at its best with a music server.
I wish I had some single song that would allow me to illustrate the differences between the two DACs. It’s just not that simple. They both are really excellent in very different ways and the way you get digital files to them, optimally, appears to be very different. Plus they just suit different systems. So when you go into your Ayre store, don’t evaluate the two DACs in exactly the same way. Contrast and compare. Do your homework. Oh, wait. I just looked at the Ayre product page and it appears that both the QA-9 and the QB-9 DSD are no longer in the product lineup. I hate to be the harbinger of doom, and I have heard great things about the QX-5 Twenty streaming DAC, but I think dropping those 9-series components could be a big mistake. Unfortunately, not my decision to make.