WAS working fine but seems lost part of listening...

About a month ago had a small smell of burnt electronics and thought it was from the new TV I bought, but nothing was wrong. Yesterday heard my power regulator for the computer complaining (beeping) as if either I got a huge voltage spike in my electricity (or maybe something shorted somewhere) but the lights or circuit breaker of the house did not go out. Then at night went to listen to receiver and I notice the it was working partially. This is, everything works, sound through all channels, etc BUT it has lost VOLUME this is when volume at 35 out of 60, it sounds like 10 out of 60. Also it lost definition, the sub for example seems to have frequency missing. Could it be that some audio/output amplifier IC burnt? How many IC amplifier does this unit have? If one burnt would the symptom be as describe above?  Am I in the right direction to what is my receiver problem? Any help would be appreciated. Thanks