Question Motherboard issue?

[Darkshotz]

I've been having some trouble with my PC as of late. On startup display cuts in and out (tried with 3 different GPUs, same result). Sometimes it doesn't happen, and PC starts like normal. Then the problem is a high pitch constant noise coming from any device I plug into the audio jack(no other audio, just the high pitch thing). Problem persist after multiple driver re-installs, and different settings in BIOS. PC seems unstable and unreliable. Motherboard is an Asrock 970 pro 3.0. I have an FX 6300 CPU on it. I tried a Radeon HD 5570, ASUS r9 270x, and a GTX 1050ti GPU. Got 2 sticks of 4gb 1600 mhz ddr3 ram. Tried those in all sockets, single and dual channel. Nothing.
After my hours long troubleshooting, is there something else I should try, or, as I see it, the motherboard is dead/dying, and needs replacement?

 

[rgd1101]

make and model of the psu?
check cpu/gpu temp?

 

[Darkshotz]

pretty no-name PSU, enough watts, but not bronze or whatever certified, but I managed to get the GPU to work , so it seems unrelated. Temperatures are good, both CPU and GPU about 5-10 above ambient. When I turn off the realtek audio manager, I get an awful popping noise. If it's on, there's no sound, just the high pitch noise and some static. I also have a jack on the front of the PC, but there it's even worse. Could the sound part of my motherboard be dead?