I have a string of leds hooked up together with the correct resistors in parallel, going out to a TIP31 transistor which then goes to the power cord and to a 3mm jack. This 3mm jack goes into my computer and my leds "dance" to the music, I assume is the change in voltage. Anyways, I have hooked this up to one of my computers and it works flawlessley, but when hooked up to my other computer, the LEDs light up very bright and do nothing else. I am not sure how to begin debugging or how to fix it. If it makes any difference, I am using a sound card in the second PC. Any nudges in the right direction or solutions are appreciated.