3.5mm to RCA cable suggestions.

You're welcome, Asahitoro.  Regarding whether or not a power cord upgrade may benefit this particular speaker, though, I have no idea.  In addition to depending on the design of the speaker's two internal class AB amplifiers, and on the characteristics of its stock power cord, it could conceivably also depend on what the AC line voltage happens to be at your particular location.

Good luck.  Regards,
-- Al
 

The same comments I had about XLR vs. RCA apply to the Kirlin 3.5 mm to dual TS (not TRS) cable linked to above, vs. RCA. Also, I’ve never liked 1/4 inch connectors because in my experience the contact they make can sometimes become intermittent, especially if they happen to be jiggled.

Regards,
-- Al

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

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 have the options of balanced, unbalanced and 1/4" TRS on my monitors. Which is the best route to go?

As can be seen in the block diagram on page 13 of the MR8 manual its XLR and TRS inputs have an additional active stage in the signal path (probably an op amp) which the RCA input doesn't have.  Given also that you will be supplying the MR8 with an unbalanced signal it would therefore most likely be best to use the RCA input.

I might add a small tube preamp after the DAC and before the speakers.

Keep in mind that like a lot of pro-oriented solid state equipment the amplifiers in the MR8 have relatively low input impedance, which many tube preamps will not be able to drive without significant deep bass rolloff, and/or undesirable phase shifts at deep bass frequencies.  In this case the input impedance is specified as 10K unbalanced and 20K balanced.  The balanced input impedance most likely reflects the sum of the input impedances of the two balanced signal lines, so if you were to supply the balanced input with a single-ended signal the preamp would see the same 10K load as if it were driving the RCA input.

To assure that won't be a problem you would want to choose a preamp having an output impedance of no more than 1K **at 20 Hz**.  Output impedances are often specified at a mid-range frequency, such as 1 kHz, and in the case of many tube preamps (and some solid state preamps) the impedance at 20 Hz is MUCH higher than at mid-range frequencies.  If Stereophile has reviewed the preamp the measurements section of the review will usually indicate the 20 Hz output impedance.

Regards,
-- Al