Topic: Cause of audio hum: laptop power cord/transformer
I actually read this on here somewhere, which is how I realized it was my problem, but I forget where I saw it, so I will mention this again. I bought a Behringer "hum destroyer" because everything I did left an annoying midrange buzzy hum coming through my monitors without it. When I upgraded the audio interface, hoping to get rid of it, the hum destroyer really noticeably weakened the entire signal, so that all the pianos sounded a little remote (clean, but not loud enough). Then I remembered reading that the power supply to a laptop can cause this kind of ground hum, and I realized my Taiwanese laptop was using an aftermarket power cord/transformer. So I got a hold of the original equipment model, and presto, problem disappeared.
If you get audio hum no matter what you do, unplug the power supply. If you don't get it with your laptop running on battery, that's the problem. But I found that running PTQ on battery has its own problems (weird occasional drop-offs, and even running the controller with its own power, the battery barely lasted an hour and a half). So if this is your problem, I suggest you replace the power supply cord/transformer with a better shielded model. More or less in this respect you get what you pay for, so you can probably find something that will not do this.
