3.5mm to RCA cable suggestions.

Al, thank you so much for the very helpful info. I had to read it a few times to understand it as my electrical expertise isn’t that polished. I was considering a headphone type tube preamp like this:
https://www.amazon.com/gp/product/B00A2QMAI2/ref=ox_sc_sfl_title_1?ie=UTF8&psc=1&smid=A1V014...

Here’s a good review of it:
http://www.head-fi.org/t/284835/review-of-the-little-dot-mkii-tube-headphone-amp-pre-amp

Connected to this which would be connected to my MacBook Air via USB (or BT from other devices at times):
https://www.crutchfield.com/p_703BEETLE/AudioQuest-Beetle.html?tp=59309&awcp=1t1&awcr=105211...

So it would be: MacBook Air to DAC via USB, DAC to preamp input via 3.5mm/RCA, preamp output to speakers input via RCA.

I thought maybe it would be fun to experiment and tinker with as I’ve never had any tube equipment. Again, I don’t want to dump a lot of money into this or I’ll just go buy a pair of LS50 Wireless speakers. I made a bunch of assumptions that it would work. I used to have a pair of M-Audio BX8s that I used a 3.5mm to TRS cable with and I had TRS->balanced plug adapters on it as well. It sounded excellent but I’m sure I wasn’t taking advantage of any balanced cable benefits.

Thanks again for your experienced advice.

The specs on page 7 of this manual for the Little Dot MkII indicate an impedance for its RCA outputs of 600 ohms, with no indication of the frequency on which that is based. Most likely it is based on a mid-range frequency such as 1 kHz, and I wouldn’t be surprised if the impedance at deep bass frequencies rose to amounts that are much higher than 600 ohms, and that are too high to be optimal in conjunction with a 10K load. Although the MR8 can’t reproduce much of the bottom octave (20 Hz to 40 Hz) anyway, so the impedance issue might not be noticeable even if present. If it were me, though, I wouldn’t purchase the Little Dot unless it could be returned without a restocking fee or other penalty.

Good luck, however you decide to proceed. Regards,
-- Al

" I am probably mistaken, but I though there was a problem going from unbalanced to balanced without proper grounding."

You have it right. That's why you can't run a component balanced and SE at the same time. That's why most fully balanced components have either a switch, or jumpers you insert in the xlr jacks directly to run in SE mode. 

Regarding proper grounding, I would expect that a stereo 3.5 mm to dual XLR adapter cable, such as the Hosa cable the OP linked to earlier, would accomplish that. Presumably it connects the ground of the 3.5 mm plug (the "S" of its TRS connections) to pins 1 and 3 of both XLR connectors. Pin 1 is the ground connection of an XLR input, and pin 3 is the signal pin that should be grounded when an XLR input is provided with an unbalanced signal.

The cable presumably also connects the "T" (tip) of the 3.5 mm plug, which conducts the left channel signal, to pin 2 of the XLR connector that would be connected to the left channel speaker. And it presumably connects the "R" (ring) of the 3.5 mm plug, which conducts the right channel signal, to pin 2 of the XLR connector that would be connected to the right channel speaker.

That would all function in a reasonable manner. However, for the reasons I stated earlier connecting via RCA would most likely be preferable.

Regards,
-- Al

Here is the 3.5mm/TRS also:
http://www.musiciansfriend.com/accessories/kirlin-original-y-cable-3.5mm-trs-plug--2-x-1-4-in.-mono-...