Moding Parts Express Amp

Modding the Parts Express amps really is a rather simple procedure. All you have to do is change out two resistors. These two PDF files tell you what resistors to change, and what to change them to for various boost and rumble filter options.

First thing you have to do is remove the screws holding the plastic casing in place (300-792 only). These screws are marked with red in the first picture. There is a connector, attaches the wires from the amp to outside of the plastic casing, you have to disconnect to completely separate the plastic case from the amp (second picture). Then you need to get the circuit board that has the two resistors off. As you can see from the second picture all that is visible on this board when attached to the steel plate are the solder contact points. To remove it you need to disconnect the wire harness going from this board to the vertical one (just a simple plastic connector that needs to be pulled apart). Remove both control knobs (marked with blue in first picture) and the nut and washers behind them. Then you have to take out all the screws marked with yellow (first picture). The result is then shown in the third and fourth pictures. One one of the two amps we had to bend the vertical board back a bit to get the board we were after out.

With the board out all you have to do now is swap out R26 and R27 (with the values for your choosen boost level and rumble filter corner frequency). The first two pictures have the areas were these two resistors are circled and next two are close up of those areas. In both cases the resistors have already been changed.

Reassemble everything and your done. Nothing to it.