Has anybody tried using single solid core cables?

Tried them went back to my STEALTH V14 much better detail.

I am currently using solid core wires only. Of all the cables tried, they seem to follow along the tunes better. When it comes to wire design IMO less is always more. It is not uncommon for Hi-Enders to try a variety of cables within the same price range only to find the sound to be different and not necessarily better. Wire companies know that only too well, and they excell at selling different sounds and not necessarily better.
As for me, I try to focus on simple designs coupled with high quality cables, the little known Shishido silver and copper. All single wire (as opposed to multi wire, solid core which IMO is tantamount to stranded wire). The sound is dense and musical, sweet and organic without being sirupy or veiled whatsoever. I wouldn't dare venturing again in that maze of solid vs hollow ribbon vs geometric etc. etc.

Since my earlier post about using all solid core, I did a tweak. Brass conducts less effectively than copper, and I so I took my cheap banana plugs out of the loop. I also used DeOxit on all of the connections. I'm getting better highs now.

On using romex or "HomeDepot" wire, there is a drawback. Larger gauge copper has skin effect, and the wire will also oxidize quickly compared to OFC.

I concur on removing the terminations. My Mapleshade Double Helix are simply bare wire and sound all the better for it. I've read on other sites where some have removed the terminations on their Anti-Cables for better sound.

As for gauge, the Mapleshades are around 18 ga which seems to hit a sweet spot of sorts. Works like a charm.

All the best,
Nonoise