If you have a tube amplifier you need to have a high quality cable to ensure that you're reaching the full potential of you amp. Stop using old computer cables and move up to a 12 AWG high quality power cord. There is a sonic difference when using a cable that allows the cable to let power flow unrestrained. Most cables supplied with amps are only 18 AWG cords and your house or venue is wired with at least 14 AWG.