Best practices when conducting a DAC comparison

David,
I have now owned and auditioned a Bryston BDA-3, Luxman DA-06, and the Oppo 105d with its internal DAC.  Each, as you know, uses a different DAC chip: respectively AKM, Sabre Burr- Brown.
I now use exclusively the Bryston, sourced via USB by a Bryston BDP-3 streamer, or the Oppo disc player via HDMI.
The characteristics of these DAC's has been described by others, and there may be general agreement that the Luxman is 'very smooth', the Oppo (sabre) detailed but harsh, the Bryston in-between.
My personal impressions:
1. The Luxman employed for chamber music...string quartets, piano trios and quartets...
is 'muddy'....the lack of detail increasingly becomes annoying.  Its employ for solo piano invites similar comment.  Try as I might to persuade myself that the 'more expensive sound'...ie, the Luxman's...should be better than the Oppo's, I had to throw in the towel and
avoid the Luxman for strings and piano.
2. The Luxman employed for voice is a delight.  I've read of various hi-fi components
that a 'smoother' high frequency response decreases listener fatigue.
Such comment applies to the Luxman used, for instance, for listening to an
opera DVD.
3. That virtue is such that even 'downrated' DVD audio sourced to the Luxman via the Oppo's coaxial audio output was superior to the Oppo's internal audio decoding of opera DVD's,
including blu-ray DVD's.
4. The Bryston BDA-3 is a good compromise...' 
I struggled to parse the foregoing impressions in respect of digital source format...standard CD, SACD, hi res PCM, double speed SACD.   The sound quality seems to improve as one progresses from the beginning to the end of that list, but the DAC comparisons...at least my ear...are the same. 

A most excellent list, Steve.

The question that bugs me is that of optimizing each component for best results. Should David use a reclocker for both pieces in the comparison even if one benefits and the other doesn’t (assumedly because the latter has better addressed the issue of noise and jitter reduction internally)? Does that fairly represent the potential user experience of each? What about different cabling/power cords that optimize each independently?

The purists’ "apples to apples" mentality would seem to require that the exact same cabling (even using the included power cords and perhaps generic digital cabling) with no external devices in play. Sounds fair, but what if one component would benefit tremendously from a reclocker or specific cabling to the point that it significantly outperforms the other and/or changes David’s preference? Even worse if one is much less costly than the other and investing a relatively small amount (i.e. that the total investment would be significantly less) would make it equal or even to outperform the much more expensive competitor.

The Terminator lists for ~$4400 and the Yggsrasil for $2400. Would spending less than $2k to optimize the Yggdrasil with a reclocker, cabling, etc. yield a better sonic result, thus making it a better purchase decision for the same or lower investment?

Seems that in the "bang for the buck" approach that the answer would be to address this with a "same or less total cash outlay" comparison as this is the real world dilemma for many of us. But then there are those that will choose to use each without any "supplements" (reclockers or upscale cabling, etc) that would find value only from the "apples to apples" comparison. And also those seeking an "all out assault" that may have interest in an ultimate sound quality comparison with each having every enhancement specifically optimized for that particular component regardless of cost. Who, short of the most diehard professional reviewer, has a sufficient number of these ancillary components available to even begin to satisfy all possible curiosity?

David has a real challenge on his hands trying to potentially satisfy each category of reader. I wish him the best of luck.

Dave

Thanks to everyone for your guidance and to the recent helpful posts from @seventies @audioengr  and @dlcockrum 

I've learned much from each poster.

I finished the comparison between the Schiit Yggdrasil and the Denafrips Terminator this morning. The comparison got held up for a number of reasons but all-in-all the delays, in retrospect, were actually helpful and made for a stronger and more robust evaluation.

First, I was able to get to a place where all the components were well broken in.

Second, I was able to spend significant time with my system and each of the 'newer' components and cabling and I now have a very good feel and sense for them. 

Third, though the comparison is Subjective, I was able to control many of the variables to level the playing field --- as much as I reasonably could; however, the review process will not meet bench level rigor.

Fourth, the added time has allowed me to think through and reflect on the process and what I'm looking to achieve much, much more thoroughly. 

Fifth, I was able to get another audiophile's perspective on where my system is 'performance wise' as well as getting feedback on shortcomings. I also wanted a second opinion on What I 'hear' and How I 'hear' and to discuss my audio preferences 'live' and based on my system. I've also had a number of phone discussions with audiophiles active on Audiogon to answer questions and bounce thoughts and approaches off of.

I will be writing up my findings and takeaways starting tomorrow and should be able to wrap it up over the next few days. Once it's finalized, I will post a link for those who may be interested and curious.

Hey guys, my write up is posted here:

http://terminatorandyggdrasil.blogspot.com/

And here:

https://forum.audiogon.com/discussions/denafrips-terminator-and-schiit-yggdrasil-evaluation-and-comp...

This thread guided my approach, though it is not as rigorous as some suggested or how you might conduct your own evaluations.

The suggestions, however, certainly became part of the process and for that I am thankful and grateful to all who posted. I learned a lot through your feedback. Thank you.