Mixpro Dual-Channel Belt-pack Preamp

The MixPro Dual-Channel Preamp is a tiny, belt-pack style acoustic preamplifier that packs a lot of features in a lightweight and compact package. In addition to its passive* bass and treble controls, it has a tool many bass players find a necessity: an adjustable low-cut filter. The MixPro also has a phase control, as well as the ability to supply the 9v phantom power that most mini condenser mics require. While aimed at acoustic guitar, its feature set makes it an excellent choice for use with upright bass.

This preamp is ideal for blending two pickups, or a pickup and a K&K Golden Bullet mic - the preamp can supply the 9V phantom power required for using those mics, and we can put together a "kit" which includes the splitter cable, the preamp, and mounting gear so the preamp can be attached to your bass tailpiece.

This preamp is also suitable as a replacement for a lost/broken preamp for any of the K&K two-element systems like the Golden Trinity Mic/Pickup Systems, Bass Master Pro, or Bass Master Rockabilly.

The one feature that you may miss is the ability to EQ each channel separately; the EQ on the MixPro is "Post-Mixing" - meaning that it EQs the blended signal, not each channel separately.

Features

1. Works with just about any pickup combination including mini mics
2. Small, lightweight design can be clipped to belt or attached to microphone stand or tailpiece
3. All class A circuitry for sweet transparent sound
4. Identical input stages on both inputs will work with passive or active pickups and mini mics giving you an array of possible configurations
5. Output phase inversion at fingertip access helps control feedback
6. Switchable phantom power to either or both channels
7. Variable master low-cut filter (trim control) is tunable from 27-225 Hz (12 dB/Oct.) and is a powerful tool for taming wild pickups or sound systems
8. Internal relative phase switch for the optimum blend between two sources
9. Variable gain for both tip and ring channel to match most pickups and mics
10. Mono mixed output

Features:

We've added our own notes to some of the feature keys on the illustration in the photo array, to better describe their use in the real world.

• A. Treble: passive*
• B. Bass: passive*
• *Passive tone controls can throw those of us used to active tone controls for a loop, since they behave differently than one might expect. Lots of preamps have active EQ controls, meaning that they boost or cut a specific band of frequencies using active and extra circuity to accomplish it. However, old school instruments, for example, have a tone knob that is passive, meaning at the full-on position you get all the frequencies, and rotating it the other way cuts that frequency band. That's how the treble and bass controls on the MixPro work. So, start full-up and trim away highs or lows as needed.
• C. Trim: The Trim Control is an adjustable 12dB/octave low cut filter that is adjustable from 27Hz to 200Hz. Also referred to as a High Pass Filter, this useful tool lets you choose a frequency and gently suppress notes below that choice. It's ideal when your pickup is sending a lot of "rumble", "boominess", and useless lows that muddy up your sound.
• D. Volume Control that affects the output signal sent to the amp or next device.
• E. 1/4” Output: This is a regular unbalanced output for a standard mono cable. A standard mono cable is necessary as it switches the preamp on.
• F. Invert: This control changes the polarity, also described as phase, of the signal. Reversing phase can often get you a few more dB when you are close to feedback.
• G. Battery Status LED: The battery status LED remains on at all times when the unit is plugged in. As the battery weakens the light will gradually dim.
• H. Mix Control: Adjust the blend amount of the two input sources.
• I. (internal) Phantom Power Switch: If you are using a mini-mic that requires phantom power, open the Mixpro's case. The phantom power switch is adjacent to the input jack.
• J. (internal) Gain Control: The adjustable gain allows you to tailor the preamp's performance for lots of boost for a low signal pickup, or trim gain back to handle a very hot signal, such as an instrument that has an onboard preamp.
• K. 1/4” Input: This is a 1/4" input for a stereo/TRS instrument cable.
• L. (internal) Battery Compartment: To change your battery, remove the two screws adjacent to the belt clip using a screwdriver or a dime. Slide the preamp out of the housing and replace the battery.

Specifications:

• Size: 4.75 x 2.85 x 1.25
• Weight (with battery): 7.3 oz.
• Battery Type: Single 9V
• Power Consumption: 2.3mA
• Battery Life: 200+ Hours
• Class: Pure Class A, all discrete
• EQ: Passive
• Treb: +/- 6dB @ 7kHz
• Bass: +/- 6dB @ 80Hz
• Low Cut: 12dB/oct.
• Gain (flat EQ): +6dB to +28d
• Signal-To-Noise: -90dB, 27Hz-20kHz unweighted
• Input Impedance: Phantom Off: 10 Megohms/Phantom On: 15k
• Output Impedance: 800 Ohms