This modification will require you to open the 528E and make a change internally. You will need a #2 Phillips-head screwdriver.

Top cover removal:
1. Ensure that the 528E is disconnected from the AC power source.
2. Remove two 6-32 x 1/2 inch screws from the top panel and two 6-32 x 1/2 inch screws from each side of the chassis.
3. Lift the top cover free of the chassis.

Changing the XLR output level:
1. Remove the top cover according to the steps outlined above.
2. As you look at the unit with the front panel facing you, locate the OUTPUT LEVEL switch (SW7) in the upper right side of the unit just below the XLR output connector.
3. Push the switch in to select MIC level output or out to select LINE level output.
4. Replace the top cover.
5. Reinstall the 528E into your setup.


You can also find an article on how to do this, along with a block diagram of the inside of the 528E, here.