sound card

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...

Hey, I already own a Scarlett 2i4 from Focusrite and I've been wanting to switch out my old half broken hd598s for some dt 990 pros. Can I hook up an ext. Headphone Amp to it and if so how would I go about doing so?

Hello all, I am interested in buying an external sound card for my DELL laptop since I am very upset with its sound quality. However, I have wireless Bluetooth headphones set, and I couldn't find any sound card that supports wireless headphones, Can you advise please? Thank you.