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

Input
The input is designed to accept a wide range of sources from passive to active instruments as well as from an acoustic bass pickup. This input is AC coupled to prevent unknown sources from damaging the input circuitry with DC or spikes. The rest of the circuit is DC coupled all the way to the output.

Mute Switch
The mute switch mutes the input at every output except the tuner out. When the channel is muted, the Red "clip/mute" LED is illuminated so you know that you’re in “Silent Tuning” mode.

The Gain Control
The gain control sets the gain level into the EQ. Input gain is staged in a special multiplicative arrangement. The first stage is a fixed gain multiplier and the second is a continuously variable gain control. The gain OR attenuation in the input stage is achieved actively. As the Input gain control is increased, the gain produced is multiplied by the fixed gain in the first stage. The advantage is that neither stage is burdened with the duty of producing all of the input gain. This allows the already high performance circuits to operate very comfortably without strain. The gain components: chosen are capable of performance that exceeds those found in the majority of bass preamps on the market by factors of 10, and often by 100. The result is a super quiet, super clean signal path.

Red Clip-Mute LED
As mentioned earlier, when the mute switch is engaged, the light comes on and stays on until you remove the mute function. Additionally, when the signal level is too high, it will flash letting you know that you are in overload. NOTE: the clip light gets its input from the point after the EQ and before the master volume. This is the last point in the signal chain where level can still be increased. So, set your EQ first for sound, and then set the input gain as high as you can before clipping. Set the actual playing level with the master volume control.

Pad Switch
Engaging the pad switch removes the first multiplier stage, leaving you with only the continuously variable gain control, set to deliver only as much gain as you need which also helps keep noise and distortion to a minimum.

DI Gain Control
The DI gain control sets the level being sent to the direct out. This is the pre-EQ signal that should be used to send a signal to the house or main sound reinforcement system. The DI is not a step down stage. The level coming out of the DI is the same as that going in so bear in mind that you have the capability to overdrive the house console. Keep the levels moderate and encourage your sound man to do his job and use a pad at his end.

Pre-Post Switch
The PRE-POST switch allows you to select whether the signal going to the DI gain control comes immediately after the PAD switch circuit or after the EQ circuit (which is also after the Effects Return). Bear in mind, when POST is selected, changes to the INPUT GAIN control and EQ will affect the DI level. The DI GAIN control never affects the "amp" level, however.

Tone Shaping Circuit
The Tone Shaping circuit in the MPP line is a 4 band boost-cut design. Every great engineer will tell you that it is better to cut than to boost as boosting a signal adds noise and potentially distortion. Try adding gain in small increments to increase a certain frequency range and then build around that as a basis for finding and shaping your sound. There are no hard fast rules but I will say that this circuit it is not designed to have every control turned all the way up.

Treble Control
The treble control determines the amount of the upper frequencies added to or subtracted from the original signal. Setting the control to "12 O'clock" will reveal a center "click". This is flat, or no boost or cut.

Air-Crunch Switch
The air - crunch switch moves the frequency range of the treble control. The "air" position is a very high setting for accentuating the upper "sizzle" part of the sound, or for cutting string noise without losing any upper midrange punch. Try this setting if you’re looking for a very “glassy” edge when slapping and popping. The "crunch" position brings the frequency down to an area where boosting it will bring the upper range more forward. Try this when you’re looking for more of a “grind” type of tone - great for a very aggressive sound or for bringing back brightness to a cabinet that lacks upper mids and low treble. Cutting gives sort of a "passive tone" feel. Both settings are shelves, so even the crunch setting delivers nice extended highs along with the lower treble push.

Edge Control
The edge control is a specialized upper mid whose job is to bark when boosted and give a nice slap scoop when cut. This is the “instant gratification knob”. Setting the control to "12 O'clock" will reveal a center "click". This is flat, or no boost or cut.

Midrange Control
The midrange control determines the amount of the middle frequencies added to or subtracted from the original signal. Setting the control to "12 O'clock" will reveal a center "click". This is flat, or no boost or cut.

Punch-Round Switch
The punch - round switch moves the frequency center and bell shape/width of the midrange control. The "punch" position is in the "boxy" register and is an alternative to the edge switch which is contoured for a slap scoop. It also does a good job of dialing "honk" out of a bad cabinet when cut. Boosting it tends to make the sound take up more space – experiment with this and you’ll be amazed at how powerful this feature can be. The "round" position is 'low and wide'. It's designed primarily for boosting when a FAT finger sound is what you need. It makes a bridge PU by itself sound much bigger. On a fretless bass it's like a "MWAH" maker. This frequency with a deep bass boost and a high treble cut gets you a nice dark and funky kind of sound.

Bass Control
The bass control determines the amount of the lower frequencies added to or subtracted from the original signal. Setting the control to "12 O'clock" will reveal a center "click". This is flat, or no boost or cut.

Thick-Deep Switch
The thick - deep switch moves the frequency range of the bass control. The "thick" position, or booty-shaker, is designed to give most of the notes in the bottom couple of octaves of the bass more "breadth" while still adding low support. The "deep" position gives a rounder response to the control, adding only size to your sound without keeping the notes from speaking easily. Both settings are shelves, so even the "thick" setting delivers nice extended lows along with the upper bass push.

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Master Volume Control
The master volume control is an attenuator. There is no gain available here. Use this control to set your on-stage playing volume.

The Master Mute Switch
The master mute switch mutes your on-stage signal, leaving the DI output and headphone output on.

Blue Power LED
The blue power LED should be illuminated when the unit is on. If the 120V/240V switch on the rear power entry module is set incorrectly, this LED will not light.

Headphone Monitor Controls
The MPP-1 now allows you to plug a stereo source (say a mix from a live or studio console with NO bass) into a balanced stereo input on the rear panel and mix it with your bass signal while sending independant signals out of the DI and to the amplifier or shaker.

Bass
Here you control the amount of the bass signal being fed to the headphones.

Line In
Here you control the amount of the STEREO signal at the REAR PANEL line input being fed to the headphones.

Headphone Output
The headphone output is something to talk about by itself. It will drive ANY kind of headphones with a mix of the line in and the post EQ bass signal to the point where the phones will shake right off your head, although I don't recommend this! The level of the bass into the phones is controlled by any control on the preamp. This output is true stereo.

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Power Switch
The power switch interrupts power to the primary side coils of the power transformer. It's the first thing the power line sees after the main power fuse.

Geek Related Technology
The MPP-1 input impedance is 1,000,000 ohms unbalanced and the direct output is driven by a top-of-the-line Burr-Brown balanced line driver with a distortion specification of <0.00005%. While you may never have to drive a 600ohm load to 17Vrms across 500 feet of cable, now you can. An optional Jensen transformer adds true galvanic isolation between your rig and the house rig. The main output is driven differentially by a proprietary ultra-high-grade differential driver. The circuit boards are multi-layer designs with isolated ground, power, and shield planes. Most parts are surface mount, affording a small footprint and very short traces which means very little parasitic capacitance or inductance. This keeps the circuit operating in a highly linear manner except when you don't want it to (like when you turn an EQ control). Signal path capacitors are highest grade, film caps. The power supply capacitors are tantalums and aluminum electrolytics. The power supply is bipolar, double regulated for superior stability and over-voltage protected. Noise was measured at 97dB below signal. Distortion is effectively non-existent, frequency response is flat within a small fraction of a decibel from 20Hz to 20kHz. Bandwidth is extremely wide with the upper 3dB down point being at 40kHz.