The burned resistor looks like a metal film resistor, but I can't tell the value as the color bands are too burned. The important thing to know is that the resistor likely burned up because there was too much current passing through it. So, you will need to find the cause of this and repair the problem. The burned resistor is just a symptom and replacing it won't fix the problem. Take the amp to a tech in order to sort out the problem and have it repaired.
