I've recently got a new IPS 16-bit Pocket MD HD and noticed the sound is mixed badly with some sound effects being a lot louder then the back ground music. After some research I've found it is because of the wrong resistor values used to do the audio mixing. I've found a few different forums and YouTube videos saying to use different resistor values as showing below. I think I'll have to take input from them all to work out what values to use. 

Japanese forum

Before modification:
FM input resistance: 10kΩ
PSG input resistance: 10kΩ
Feedback resistance: 100kΩ
Feedback capacitor: Unknown

After modification:
FM input resistance: 33kΩ
PSG input resistance: 68kΩ
Feedback resistance: 120kΩ
Feedback capacitor: 47pF
 

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