Has anybody tried using single solid core cables?

I'd like to add my 2 cents to the long list of responses above, pertaining to solid core cables vs. "whatever".  I have a considerable collection of interconnects and speaker cables of all lengths, aquired over the past 50 years. All of them, different designs, based upon bundles of stranded copper and silver plated wires, and almost every concept of insulation, isolation and shielding imaginable.
That said; - - -  along the way, (about 20 years ago) I stumbled into an ad in Stereophile (I think) for a small private company in Florida who was making and marketing Solid core, twisted pair, enameled high purity copper speaker cables, terminated with your choice of quality bananas or spades. The thing that caught my eye was the price. At that point in time I was using 15' speaker cables (due to routing requirements). I called the owner and he said he could make me a pair with bananas and ship them out same day. He even said that I could ship them back for a refund if I didn't like them. And the price was $25.00 for a pair. MY God, how could I not check them out.
When they arrived I just about sh _ _ my pants!! They were so stiff, he might as well used 1/4" copper tubing. Insane ! It never dawned on me that they would be that gnarley. With the way my system was set up at the time there was no way I could use them. Wasn't worth sending them back. So I just coiled them up; - - put them in a box and stored with the rest of my "collection":.
Next encounter ! - - - - about 7 years ago, I ran into a person at an audio show, who said he was a officer of the Chicago Engineering Society. He had in his hand some bold looking (RED) interconnects with VAMPIRE RCA's. We talked about his theory and experiences while developing these cables. Once again they were constructed of heavy gauge enameled solid core OCC high purity copper wire in twisted pair configuration. I thought to myself (Oh no, not this again). So the fellow lived near me and suggested that I take home a pair and try them for a week. Then, either buy the or return them.
O.K., why not!  After a week of some extensive listening and "fiddling", I was so impressed with most of the characteristics of what I was hearing that I handed him $50 and kept them. 
Well, wouldn't you know, over the past 7 years they ended up in storage also. - - - - - until two days ago !!
Very recently I have listened and investigated MORROW cables. A friend bought a pair of phono cables and was amazed. M-M-M-M This is one I passed up. Should I give them a try? O.K. , so I did. The one drawback being that MORROW claimes that some sort of "MAGIC" is supposed to happen after 400 - 600 hours of breakin. Of course they could speed that up with a burn in cycle for a considerable price. I didn't pop for that.
Been using them for a couple of months now, with some mixed results. There were days when they sounded odd; - - almost muddy, but then cleared up. "What's going on here" MORROW said that would happen.
Anyhow to get off the subject of MORROW, - - - - - - -
Three or four days ago, I decided to start cleaning out my collection of audio artifacts. In doing so, I ran across the old RED "ALLIGATOR" cables, as I fondly called them. You know, - - - - I never actually tried them. Well one of my current setups is pretty much modular with components in a open rack. Plenty of room to fool around. So, I disconnected my MORROW'S and plugged in the "RED ALLIGATORS".
Didn't have to concern myself with them lying on carpeting because they are more than stiff enought to suspend themselves. Subsequently, I discovered my RED interconnects, also solid core. You know, I never tried using all solid core through the entire signal path.
To end this long pile of sh _ _ ! After warming up the system for about 1/2 hour, I though I'll try a little serious listening. After about 3 minutes of listening to a VERY familiar CD, I stopped ! I have to try another CD that has always sounded a little harsh, being too closely mic'd. 
All I have to conclude with, is the results were astonishing to say the least. Without any rservation, I was hearing the best overall sound I have ever heard out of my system. ROBUST; VERY DYNAMIC; while at the same time, sounding PURE and TRANSPARENT without any noticible harshness in music passages that had always been there with virtually every combination of wires I have ever tried. Dimensionality of voices and instruments were well placed with appropriate emphasis, in a 3D soundstage, more so that ever heard previously.
You can call what I have said here, a pile of "bull".  Also keep in mind that what I have done here would not be very acctepable to most audiophiles for any number of reasons, but - - - -  If anyone out there is curious enough to locate similar cables and try what I discovered, I believe that you to will be astonished at the totally beautiful sonic presentation. THAT'S IT !!

I have been wrestling with cable connectivity for many years now. Recently purchased several MORROW cables after reading all of the reports. Their design approach was different than other cable manufacturers I have tried, and been and been left with that "lack luster" feeling, just shy of dissapointment ! Anyhow, MORROW'S cables sounded at least as good as the best I have tried, right out of the box with minimal break in. I was set back a bit, by their claim that the cables had to be broken for 400-500 hours to reach their peak performance. Basically, after several hunderd hours, I did some very detailed A/B tests with the MORROW cables against my other three top performing cables. The results were somewhat mixed. Bottom line; - -  the MORROW cables sounded as good as my other three test cables, in most areas, but I honestly can't say that I found any significant increase in audible performance by comparison, as their advertisments promote.  So, on to the next step.!!

Several years ago I purchased some solid core cables that proved to be very difficult to install in my large audio console, due ti their extreme stiffness. At the time, I didn't pay much for them so I gave it up, and set them aside. A couple of years later I purchased a pair of solid core interconnects from an individual associated with the Chicago Audio Engineering Society. Very strong performance testimonies ! Again they proved to be very difficuly to route and install. I asked for a specific length, which the individual accomodated me with. Anyhow after installation and break in, I felt that the cables did sound different than others, in a good way. Without going into detail, I liked the cables enough to leave them in my system and purchased another pair. Again, as time went on, I ended up retiring them, and were replaced  with some very expensive interconnects that I managed to obtain two pair from a dealer who I had an association with, at a very large discount.  The cables impressed me in several areas and resulted in my leaving them installed as my reference cables. 

That brings me up to a couple of weeks ago.  I had some time on my hands, so I decided to do some experimentation after reading blogs pertaining to solid core versus stranded cables. 

I happened to have (lying around) A  solid core power cable that I used on and off, plus the old solid core interconnects and speaker cables. I thought, "what the hell", I'm going to try ALL solid core wiring from my power outlet; - -  the interconnect between my CD player to the amp, and then (with a great deal of wrestling) managed to route the very stiff speaker cables to my reference speakers. Anyhow, after system warm up, I thought that I would try a listening test with a couple of CD's that always had a slightly distorted, grainy sound, especialy during very dynamic higher frequencies. Well, surprise, surprise !! All the grain, strain and distortion disappeared. At first I was set back a bit, having some difficulty understanding what was going on here, and beliving what I was hearing. So I dug out several other CD's that I felt had always proven to be problematic sounding, in different areas.  "SAME RESULTS" They all sounded as though they had been "re-mastered", so to speak.  All the "grunge" was gone.  Anyhow, after this revelation,I thought I'd share this with anyone who wants to read my ramblings. It seems, at this point, that the "trick" here was using solid core wiring connections from the power outlet all the way to the loudspeakers.  When I have more time, I intend to do more A/B tests to determine, in my mind, if the premise here is valid. All I can say at this point is that the experience here was a real eye opener, and a strong accolade for the use of solid core OCC high purity copper cableing throughout an audio system. That seems to be the answer as to why using solid core, just here and there during listening tests, never yielded these astounding results.  So be it !!