Question:
I have a software download that allows me to run a guitar signal through the mic input on my laptop, and then it feeds that signal to my speaker system. It actually sounds pretty cool. I was able to download a free program that someone had made (I want to do some chorus/delay stuff).

However, since it's kinda hard on my cheap cpu speakers (and I'm interested in using this on Sunday), I want to channel the sound to my amp instead of my speakers.

I have a guitar cable with a converter on it so that I can plug one end of the cable into the headphone jack on my cpu, and the other end into the input jack on the amp. However, whenever I turn the amp on, I do get a signal when I'm running my guitar through it, but I also get a very prevelant buzz/hum when the amp is turned on. This buzz is there regardless of whether I've got the guitar hooked up or not.

Any ideas as to what could be causing the buzz and/or how to make this setup work?

Again, the goal I'm striving for is this:

Guitar==>Laptop with effects processor==>Amp

And the problem I'm having is a buzz in the amp, if a guitar is hooked up or not....

Also, the annoying buzz can be controlled with the volume knob. If the volume is muted, then there is no hum, but then that kind of defeats the purpose of an amp....

Thanks,
-t
Answer:
I'm sure the buzz is caused by your laptop's soundcard, which is probably really bad for any professional audio application.
Answer:
How sad....
Answer:
Buy a better soundcard. An outboard sound card with a higher transfer rate will improve your sound all around. It'll also decrease glitches. Look for something that operates around 96kHz. USB or Firewire probably won't matter since you'll only be doing guitar with it.
What software did you download btw?
Answer:
I need to play with the idea of using VSTs live. That would be awesome!
Answer:
Guitar directly into the soundcard? I think you need something in the middle to convert the signal into a line level signal before going into the soundcard. That probably won't stop the buzz. I use a Zoom A2 processor to go from guitar into my soundcard. I usually have to hold my bare foot on one of the metal buttons to keep it from buzzing. Best way is to use something that has a USB out. A Line 6 tone port would be great for this. Or something like this.