I should probably provide a bit of background as to what this entails, so everyone can get a grasp as what has to happen.
1) Transformers carefully removed to prevent any damage to the circuit board. These transformers are so large, they wick a lot of heat away, so removing them can be pretty time consuming without a really good soldering iron.
2) Transformers unwound as the internal cores are used to wind the new transformers onto.
3) Addition of 4 more Zobel filters to the power supply section of the amp. One Zobel exists for each leg of the transformer. The MS2250TA has two primary legs, but the original used 4. More legs means more copper cross sectional area, which means more current capability.
4) Replacement of new modified transformers.
5) Change to PWM feedback loop for higher voltage. Even though PG amps are unregulated, they are highly regulated internally. This means their rails are a ratio of their input voltage, but the amp will do everything it can to maintain this ratio. If you replace the transformers, but not the PWM feedback to the SG3525 controller, the amp will output no more power than before, but will become less efficient, as its power supply will not be optimal for the winding ratio and loading.
6) Change to op-amp 15V supply circuit. If you do not change the resistors feeding the zanier based 15V op-amp supply, the resistors will fry.
7) Change to op-amp gain stages. If you do not update the feedback circuits for the op-amps on the preamp side of the amp, the preamp will clip prior to reaching max output voltage on the amp. A few parts changed here gain you several volts of output.
8 ) Rebias the amp if need be. You should not have to rebias the amp, but I suppose you could if you chose to. Since PG amps are unregulated, they are designed to work with variable rail voltages. When I significantly increased the rail voltage of both my boards, the bias point did not change. This is pretty handy for anyone attempting to perform this mod, as it makes it one less issue to worry about.
Here is a shot of the amp in my car. It worked great for six months until a guy spun out in front of me and totaled my car. Then I became so frustrated at the loss of my install I sold everything.
