HELP! Hi-Fi amplifier feedback screech :(

[Sunthorn]

My amplifier outputs a signal, through my speakers, that sounds like the feedback when a microphone is placed near its speaker. The sound happens after about 10 minutes of the system being switched on and playing music from any source, PC or tablet. What could be causing this and any remedies you can think of? Ta

 

[kanewolf]

Bad capacitors is one possible explanation. There is no way to know without a schematic and an oscilloscope.