Audio Systems: Loud noise coming from stereo, amp output, correct numbers

Question
A month ago one of my speakers on my sony shelf stereo started only making a loud buzzing horn-like noise. I unplugged the speaker assuming that it was just the speaker going bad and decided to get another speaker, but yesterday the other speaker started doing the same thing. I went out and bought new speakers and thought this would solve the problem, it didn't, the new speakers made the same noise. Everything was connected correctly and I tried both the left and right speakers. what is wrong with my stereo? I am fairly good at fixing electronics, would this be something that if i could find the part, i could fix myself?

Answer
sounds like the amp output chip is bad. they're not hard to replace, it's the large vertically mounted to a large heatsink ic, numbers should start witk stk or similar. after you find the correct numbers on it, put them in search bar to find a seller....good luck...