Furutech speaker cables

Yes, the FS-Alpha has a purple jacket.  The Alpha is fine stranded OCC wire while the 15S uses solid-core OFC wire.

I am between the  FS-15S and the FURUTECH ALPHA-S14, that is a lower gauge of the top of the line bulk cable S25. I have a solid state amp and i have never tried a solid core cable. Furutech"s description is :

FURUTECH ALPHA-S14
 Sound characteristics:
Superlative resolution, airy, open treble, fast-paced and
highly cost-effective

FURUTECH FS-15S
Sound characteristics:
Top noise eliminator, quieter backgrounds, striking three-dimensional soundstage, solid punchy bass

I was a little confused at first. With the description above i thought that the Alpha S14 was the solid core and that the FS-15S was the stranded. Both cables are 15 gauge.

Go to Furutech's website under products, bulk cables, speaker cables and when you open each individual type of cable, under specifications it will list how many strands and the diameter of each, which you can use to determine the gauge with the table linked below.  The FS-15S shows 1@1.5mm, or one strand at 1.5mm diameter, which is slightly larger than 15awg.
http://en.wikipedia.org/wiki/American_wire_gauge

go to  audiodrom.cz to read a great speaker cable group test. The Furutech wins the test againg many other top brands like Kimber, Audioquest and Van Den Hul. The test is available in english. The Furutech had the best overall balance and it was the most musical.