Audio only coming out of RIGHT SPEAKER

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Hi,
I recently bought two Polk T15 bookshelf speakers to connect to my PC. I bought an ONEU super bass AMP to power them as well. When I set up the speakers and connect them to my phone, they sound excellent and both speakers work, however, when I connect them to my PC, only the right speaker works. The left isn't completely mute, instead, it has a crackling sound coming out of it. It sounds like the typical noise you get when you half plug in the audio jack. I am plugging the audio jack into my computer's soundboard which is part of the motherboard. How can I fix this???

I've heard the problem might be with the Realtek drivers, so I removed it, but the problem persists. Is it a hardware failure?

Computer specs:
Asus Maximus VII Hero Motherboard
Intel Core i7 4790k CPU
NVIDIA GTX 970 Graphics Card
Windows 64 Bit

Audio:
High Definition Audio Device
NVIDIA High Definition Audio
Realtek High Definition Audio