What makes for good implementation in a dac?


By now it is conventional wisdom on this digital site and others that the dac chip itself counts for comparatively little of the overall quality of the unit. The slogan has become something like: "The chips 10%, the implementation 90%." However, I cannot recall any very detailed discussion of precisely what very good to excellent to superb implementation actually involves.
Yes, there are general references to the quality of the power supply and especially to the quality of the analogue output stage; but nothing [that I can recollect, anyway] that goes deeply into the details....
So, I raise that question here. I do hope that the technologically adept members of this forum can address it, with some attention to the various dimensions of implementation, e.g. op amps vs tubes in the analogue output stage, some concrete examples of brands and models that do it well and do it badly.  
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Well, I know Ric Schultz of Electronic Visionary Systems (EVS) has never been a fan of op amps, and I have to believe he knows what he hears with them in the signal path. But I now might disagree a bit with DAC chips being less important as there has been a bit of a resurgence of R2R NOS DACs on the market that have been garnering some significant acclaim. And in that type of application, DAC chips I think become relatively more important to the final outcome. While there is obviously more than one way to skin a cat and there are certainly excellent upsampling DACs out there where maybe the DAC chip itself (as long as it’s a good one) is not as crucial in the final output in relation to other areas of implementation, I’d argue that the nature and implementation of the DAC chip has moved more to the forefront over the past few years. At the end of the day, DACs are no different from an audio system in general -- the chain is only as strong as the weakest link. This seems to be one of the few inescapable truths in high-end audio.
Here are the details of implementation that make for a stellar sounding DAC:

1) lots of fast regulators, usually discrete and not shared between circuits
2) fast logic family used to minimize added jitter
3) optimum selection and placement of power decoupling caps
4) good PC board design without ground-plane cuts
5) minimized trace lengths for both analog and digital sections, forcing the uncritical signals take longer paths
6) low-jitter oscillators when used
7) minimization of stages, both analog and digital
8) proper ground-plane referencing for both analog and digital signals
9) high-quality signal pass caps for analog, when needed
10) clever use of gates and dividers to minimize jitter added
11) optimized use and selection of op-amps and knowledge of how to make them sound good
12)  careful selection of peripheral parts, including USB chips, S/PDIF receivers etc.  They are not all the same.
13) avoiding reclocking on inputs to enable benefits of lower jitter input signals
14) careful selection of power supply technology and implementation, not necessarily all linear
15) careful use of on-board  impedance matching for all digital transmission lines
16) proper selection of impedance-matched input connectors

It's a lot like juggling a lot of spinning plates.  Every aspect is important and must be considered simultaneously while designing.

Steve N.
Empirical Audio
That’s a lot of legwork. My solution is simple. Get rid of the background scattered laser light. The visible and the invisible. You ain’t seen nothin yet.

Machina Dynamica
We do Artificial Atoms right