Audio Amplifier Overheating Causes, SSM2018T VCA Replacement, Volume Meter Integration

Hi, I have 3 questions which I need answers for as part of my project in implementing an audio amplifier system. The system is made up of 3 sub-components, namely the Voltage Control Unit, Power Amplifier and Volume Meter. I have the attached the schematic of the system here. 

1) When testing your audio amplifier system, did you encounter the overheating problem of power amplifier (PA) or Volume Control Amplifier (VCA) ? What reasons do you think that lead to this issue? Please suggest possible approaches to address the overheating problem.

 

2) The chip of voltage control amplifier (VCA) SSM2018T is an old-fashioned production. Suppose now we want to replace or upgrade the hardware, please try to find a commercial chip to replace SSM2018T while maintaining the operation of our volume control system (you can make corresponding adjustments on overall circuit design and show this in report).

 

3) The whole circuit includes two amplifier subsystems, the voltage controlled amplifier (VCA) and the power amplifier (PA). Why do we need two amplifiers? What are the purposes of using VCA and PA respectively? Can the two amplifier subsystems be replaced by one subsystem?

 

First, you need heat sink to solve overheating. Second, there are many VCA available on the market. Just look for something close to the values of your previous VCA. The adjustments to the overall is your job since this is your project also. Lastly, if you do understand the functions of an audio amplifier then you wouldn't ask this question. In simple terms, VCA is for volume control while PA is from its definition power boosting since you have speakers if your making an audio system.