ATH-M40x

I recently bought used ATH M40x headphones and they work great with my phone and laptop, but when I plug them into my desktop PC either with a USB adapter or directly into the audiojack or motherboard, I get a low frequency hum. When I use my apple headphones or my old pair of headphones...

so my current headset (steelseries siberia v2) is on its way out, and since i have a desk mic already, i was thinking of getting some decent headphones this time around. Though im not sure whether to go with the m20x to save a bit of money, or the 40x. they will be mainly used for gaming and...

For my portable use i find the cable too long, I was wondering if any of you guys know if Audio Technica sells a smaller cable. Thanks in advance.