MAC to DAC connectivity

Sorry, what is MAC?

Congrats on the new purchase. The Orchid has been getting some very positive chatter lately. For the distance you've specified I think a USB-SPDIF converter is the way to go. As an aside, I have MHDT's Pagoda and to my ears the BNC connection provides the best sound quality. I use a Bel Canto mLink which uses a proper BNC connection as it's only output. I have an Eitr as well but give the edge to the mLink. Would it be the same with the Orchid? Dunno, but it's worth investigating. Best of luck with the new DAC.

Sorry, what is MAC?

I believe he speaking of his Apple computer.

You could look at using a Dante converter/adatper. Digital input, Ethernet output, and then the reverse on the receiving end. That will let you run 20 feet no problem.

Alternatively consider a network streamer.

Yes, a Macintosh computer.

is there value in having a BNC connector on one end to the cable (dac end) and an RCA on the other?  Or is it only of value if both ends have the BNC?

Well whatever you do, you can not run USB cable longer than 10 feet  

The Audioengine D2 Wireless DAC works very well over that distance.
It has a transmitter that plugs into your Mac usb port and a receiver that you connect to one of your preamp's RCA inputs.
Of course, the DAC onboard the receiver obviates the need for your own DAC at the receiving end of the chain. [Actually, it is a pretty good DAC..... the sound quality of Spotify+ is excellent with this set-up.]
Sorry if I have changed the OP's subject of concern, since he evidently wants to transmit over the 20 feet in question from his Mac to his own DAC.
BTW, before getting the Audioengine wireless I did use a 20 ft USB cable to cover the distance.... and, contrary to one of the earlier comments, there was no deterioration of signal quality.... The set-up was simply too clumsy to live with.... thus the Audioengine.

is there value in having a BNC connector on one end to the cable (dac end) and an RCA on the other?  Or is it only of value if both ends have the BNC?

I had Blue Jeans Cable make me one and found no difference in sound quality to the standard BJC RCA model with an adapter. It was nice not having to use an adapter though. Perhaps it would be better to have a proper 75 ohm BNC terminated cable (both ends) and use an RCA adapter on one end. I currently use a Black Cat Silverstar! 75 cable and when I used it that way in the past it worked and sounded great. 

So, as the OP, here is what I am thinking:
-Run a 3 foot Schiit Pyst USB cable from the MAC to a Schiit Eitr
-Run an 18 foot Canare coax cable to the Orchid Dac
-Run short interconnects to the integrated amp
-Enjoy

I am obviously trying to build a cost effective solution compared to most of you. I think the Pyst cable is actually a Straight Wire cable. For simplicity purposes I am leaning toward Canare RCAs on both sides of the Coax cable. I could put a BNC on the Dac side, but the EItr only takes RCA jacks. The Dac can output to both BNC and RCA jacks.

Addendum to my post about the Audioengine D2 wireless: It can be used to connect one's Mac to one's own DAC [via the D2's receiver}. From Audioengine:

•  Can I use D2 to connect my computer wirelessly to another DAC in my audio system?Answer: 

  Absolutely! If you use the USB input of the D2 Sender, then connect the D2 Receiver optical output to your DAC and the D2 will act as a wireless 24-bit USB-to-SPDIF converter and stream high-resolution digital audio to your favorite DAC. You can also use the optical input on the D2, in which case the D2 will act as a wireless optical link to your DAC. Can I use a third-party (non-Audioengine) AC power adapter to power my D2 Sender and/or Receiver? The D2 AC power adapters have been specifically designed to provide stable low-noise power to the D2 so only use the included Audioengine power adapters. Using any other power adapter will compromise the audio quality and may damage your D2.

Again.... I post this with possible apologies to the OP.... This time because the Audioengine wireless solution to his Mac to DAC problem may not be the cost-effective solution he is after, since the Audioengine system costs about $399.

Thanks. It is an interesting solution, and kind of elegant....but I think I would be duplicating DAC functionality between the Audioengine and my Orchid....so it becomes less attractive from a cost and stranded capability for me (i think).

Well, it is true that you would be paying for a dac that in effect you would not be using, i.e. the one in the Audioengine receiver, on the assumption that your Orchid turns out to be superior to the AE dac. 
On the other hand, you would be able to do quick AB comparisons between your Orchid and the AE dac, simply by switching from one input to the other on your integrated amp--- I am doing it right now with my Denafrips Ares and the AE dac.... Kind of interesting.
But, seriously, I am straying from a focus on your concern as registered in the OP, namely, getting a good solution to the problem of establishing an effective Mac to dac connection over a distance of approximately 20 feet. The best solutions would involve going "wireless" over the distance, which is why I even brought up the Augioengine D2 idea.
Good luck and happy listening, Sir. 

@stuartbmw3 .. looks good. Please let us know how you like the DAC and cable arrangement. Best.

I have both USB and Ethernet interfaces to my DAC, using S/PDIF coax. I can do WIFI as well using an Ethernet-WIFI adapter.

By far, the best SQ is achieved using Ethernet, but the devil is always in the details. If you use a converter for Ethernet to S/PDIF or USB to S/PDIF, the input and output cables must be great quality or the SQ will suffer. These distances are really a non-starter for USB IME.

I would suggest the following:

1) connect an AQVOX switch to your router using a long generic CAT5 or 6 Ethernet cable.
2) Use a high-quality 0.5m Ethernet cable like the Wireworld Platinum from AQVOX to an isolator,
3) Use a EMO EN-70e isolator:

https://www.emosystems.com/?s=en-70e

4) Run a second 1.5m high-quality Ethernet cable (Wireworld Platinum) from the isolator to a low-jitter Ethernet Renderer like the Interchange:

https://www.audiocircle.com/index.php?topic=156409.0

Then run a high-quality 1.5m BNC-BNC S/PDIF cable from the Interchange to your DAC.

This will deliver optimum SQ using the shortest cables and the best converters.

Steve N.
Empirical Audio

Does anyone know if there is a way to get optical output from the MAC to the D2's optical input? I have been using the usb input and the optical out from the D2 into my Krell. Sound is pretty decent but wondered if the optical from the MAC is possible.

Does anyone know if there is a way to get optical output from the MAC to the D2's optical input? I have been using the usb input and the optical out from the D2 into my Krell. Sound is pretty decent but wondered if the optical from the MAC is possible.

@audiosaurusrex .. depends on when the Mac was built. When Apple finally released their updated Mac mini last year the optical-out was no longer. Optical-out was abandoned sooner for at least some, if not all, of their other computers:

https://www.macworld.com/article/3205890/how-to-replace-the-missing-optical-digital-audio-output-on-newer-macs.html