My amp is actually a Flextone HD...it has balanced direct outs.  In other words, no not the speaker outputs.  I've got a cabinet hooked up and run the line out separately.

The monitors work fine...they've got an 1/8" Aux Input which plays great from my computer or Ipod.

The problem is definitely somewhere with the Toneport or my settings.  I've tested the headphone output on its own, and it also produces static.

I should also mention that the sound from the software works fine, when not running through the Toneport.  If I set the default output as my computer speakers, I can play back what I've recorded.  But I can't use my computer speakers as the output if I'm running the Toneport as an ASIO input.  I'm not sure if it's ok to use the Toneport as an MME/DirectX input and the computer speakers as an output...the Line6 and Ableton setup guides both said to run the Toneport in ASIO.

I've got a USB/eSATA port, and this provides better sound, but it still crackles, and gets worse when CPU usage goes over 20%.  Even at 1-5% though, it still crackles.

Good questions.  I double-checked everything...here's what I've done to 'optimize' my settings:

• Disable my wireless connection
• Turn off any background programs in the system tray
• Disable all other sound devices (including speakers, HDMI output, HP dock) and set the Toneport as default
• Run computer in High Performance (as opposed to any Power Saver settings).

Now with these settings: the crackling is still bad if I run GearBox and Ableton Live, using the Toneport in ASIO.  The crackling is less bad if I'm only running Itunes and playing music.  If I do that, the crackles may be up to 5 seconds apart, but come in significantly louder than the music and sometimes in bursts.

This is all through the USB/eSATA port, which has better performance than my other USB ports.

I ran through all 4 segments of the video, and there were some good recommendations that I had not heard yet, but after I went through everything I still had the same problem.  The crackling may have been slightly decreased, but it's hard to tell.

I also tried a recommendation from another thread, about downloading an AMD USB filter to increase the prioritizing of resources for USB devices.  That didn't seem to make any difference at all.

Please don't close the thread.  It has been a few days because I have not had a chance to sit down and go through your latest recommendations.  I have checked all physical connections, and as far as I can tell everything is in good shape.  No visible damage, no stress/bending on any of the 1/4" cables and connectors, and the USB cable and all power supplies are in good shape.  But I have not been able to check out that video yet.  I would really like to forward this for further support but I didn't want to reply until I'd checked through everything you recommended.

HP DV4-1225dx

Any idea why that might work?

Thanks...that is very helpful information.  I'm going to mark this as 'answered' for now and hopefully this fixes it.  I won't be able to get a USB hub right away but the power issue makes sense to me, and if that doesn't work then I'll try on here again.