Please use a standard IEC power cord until you can buy or make a proper power cable. While the copper in the CAT 5 may be up to the task, the insulation most certainly is not. Way too thin for the amount of current flowing through a 120v 60Hz power cord.
Nothing wrong with a home made cable, as long as the cable you choose is made for the voltage and current you are using. That's why regular power cords have that thick rubber coating on each wire, with a thick rubber coating over all conductors. It is rated for household current. CAT 5 is not. CAT 5 can be brittle and break from too much bending, it's rather fragile compared to a stranded copper wire used in an IEC power cable. A custom cable may sound better, but a standard UL approved wire won't destroy your sound either. It'll be fine until you get a proper cable.
Nothing wrong with a home made cable, as long as the cable you choose is made for the voltage and current you are using. That's why regular power cords have that thick rubber coating on each wire, with a thick rubber coating over all conductors. It is rated for household current. CAT 5 is not. CAT 5 can be brittle and break from too much bending, it's rather fragile compared to a stranded copper wire used in an IEC power cable. A custom cable may sound better, but a standard UL approved wire won't destroy your sound either. It'll be fine until you get a proper cable.