Click here to see a large photo of the MPP-1 rear panel

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. 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: Don't. The MPP's now feature a special proprietary power supply circuit that allows the use of a non-switch mode power supply design without power factor correction that can safely switch itself to the appropriate voltage coming in from the line. No user intervention is needed. A special logic circuit energizes the coil of a relay to change configuration of the transformer primaries. You get the best of both worlds, convenience of not having to worry as you travel, and the superlative performance of a super stiff, linear power supply.

Chassis to Audio ground lift switch
This switch should remain in the GROUND position unless you are connecting the output of the MPP to a single ended load and you have any hum issues. This can work in lieu of an audio ground lift without having to lift the AC ground which can be a dangerous and unlawful practice.

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 gray pushbutton switch, when pushed in, disconnects the MPP audio ground from the device it's plugged into

Balanced Line Input
Plug a stereo or mono source in here. The signal here is sent ONLY to the headphone output and the level is controlled by the "Line In" control on the front panel. Can be balanced or unbalanced. When using a "common ground" kind of wiring like the output of an iPod, use a stereo 1/8" plug to stereo 1/4" plug adapter and plug into the left channel. Plugging a mono signal into the right channel input with the Left input empty distributes the mono signal to both channels of the headphones.

Balanced Line Input Ground Lift switch
Press this small gray button IN to lift the audio ground from the stereo source to the MPP in the event of ground loop hum.

Effects Loop

Send
This output comes right after the EQ. It is balanced but can also be run unbalanced.
Return
This balanced or unbalanced input gets mixed into the internal signal path right at the point where the POST EQ DI pickup happens and just before the
Master Volume control.
Gnd Lift
Lifts the ground between the effects unit and the MPP
Series/Parallel
This switch, in "series" mode, interrupts the internal signal path and forces the external effects into the path of ALL of the bass signal. In parallel the effects are in a "side chain". The desired amount of effect can be set with the volume of the effects themselves.

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Footswitch
Plug the optional footswitch in here and set the channel mute switch to "MUTE". Tip and Sleeve short for PLAY. Open for MUTE for you DIY'ers.

The Tuner Output
The tuner output is on at all times. 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.

The Direct Output
The direct output is a solid state pre or post-EQ switchable output driven by an industry-leading Burr-Brown differential driver with a dedicated gain control on the front panel. It is grounded at Pin 1 by default. It's ground lift switch is on the rear 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.