AC Input
AC input happens via the power entry module at the left end of the rear panel. It also houses the main power fuse and the voltage switching circuitry. To change the fuse, pop open the drawer in the lower half of the module and replace the fuse with a 250V 1A fuse. Changing from 120V operation to 240V operation: Remove the drawer in the lower half of the power entry module. Slide the small rectangular circuit board out the end of the drawer, turn it over and replace it in the reverse orientation. You'll note the voltage you've selected in a "window" in the drawer. The two round fuse holders with gray centers are secondary DC fuses designed to blow in the event that the unit is plugged into a 240V circuit while still set for 120V operation. A special circuit in the power supply diverts over-voltage away from the sensitive audio circuitry and safely to ground through the fuses. This quickly blows the fuses which interrupts both positive and negative DC power to the preamp. These fuses are both 1A 250V. Changing the secondary DC fuses: turn the gray fuse carrier 90 degrees and pull it out. Pull the fuse out of the fuse carrier and replace it with one of the same value. Reinsert the fuse carrier into the black holder and turn 90deg to lock. Check the main AC voltage where you're playing before continuing and set the voltage appropriately as described above.

The Main Output
The main output is available through both an XLR connector and a 1/4" phone connector. The 1/4" is wired "Tip/Ring/Sleeve" for fully balanced operation when a T/R/S cable is used. If a standard mono guitar cable is used, the output is unbalanced. When a cable is inserted into the 1/4" jack, the XLR connector is switched off.

Main Output Ground Lift Switch
This small silver toggle switch in the UP position disconnects the MPP audio ground from the device it's plugged into. This feature is available with both balanced and unbalanced connections.

The Direct Outputs
The direct outputs are solid state pre-EQ outputs driven by an industry-leading Burr-Brown differential driver with a dedicated gain control on the front panel. They are grounded at Pin 1 by default. A ground lift switch is available on the front panel. This output is muted when the channel mute is engaged (clip/mute LED on) but remains on when the master mute is engaged. An optional Jensen transformer is available.

The Tuner Output
The tuner output is on at all times. It is driven differentially so there is no ground connection to your tuner to avoid ground loops in your rack. There is no volume control for this output. While it is driven by a very high quality circuit, it has not been developed to serve any purpose other than to be fed into a tuner.

Click here to see a large photo of the MPP-2 rear panel