Updates
This revision of the Messenger has a few changes from the previous releases, including:
Input impedance optimized for upright and electric bass
Phase switch added at the input
Parallel output (labeled Tuner) is now buffered so that any parallel devices do not load down your instrument
The EQ Bypass switch has been replaced with a Mute switch
The stomp switches are now soft touch switches that activate relays
 
Introduction
A high fidelity gain stage cleanly boosts your signal with very low noise. A switchable clean boost gives you extra volume for when you need to stand out. The four band EQ with variable mid frequencies shapes your tone with precision and clarity. The low and high pass filters smooth the lows and highs for consistent tone for any venue. Separate level controls for the line out and DI allow you to set the perfect signal level for driving an amplifier and mixing console simultaneously. The DI features a transformer balanced out with a ground lift switch for true isolation. The internal 30 volt supply provides plenty of clean headroom for virtually any incoming signal.
 
Technical Specifications
 
Power Supply
The Messenger requires a regulated DC power supply. The voltage must be no less than 9 volts and no greater than 18 volts. The supply must be rated for at least 250 mA. The supply must use a 2.1mm barrel connector with center-negative polarity. You should choose a supply that is intended to be used for musical devices to ensure it will be low noise. There is no difference in performance when using 18V compared to 9V.
 
Input and Outputs
The input to the Messenger is a 1/4" unbalanced jack. The input impedance is 10MΩ and will work well for both upright bass and electric bass. The Phase button retains the phase when pressed in, or inverts the signal when the button is out . The Tuner jack is a buffered output, and may be used for sending your unaffected signal to another device. The line output is capable of driving preamps, power amps, effects loops, and other effect pedals. The transformer coupled DI output is specified to drive 600Ω loads or greater. Phantom power will not power the Messenger, however it will not damage the unit if applied. The Ground Lift switch isolates pin 1 of the XLR connector from ground.
 
Gain
The front end gain stage is capable of up to 30 dB of clean gain. Be careful when setting this…start with lower gain settings and only increase when necessary.
 
Boost
The boost is capable of up to 15 dB of additional clean gain. This is active when the Boost stomp switch is on.
 
Equalizer (EQ)
The EQ is a boost/cut type, providing +/-15 dB of range and is flat with the knobs at noon.
The Bass is a shelving type EQ, boosting frequencies below 80 Hz.
The Treble is a shelving type EQ, boosting frequencies above 3 kHz.
The Low Mid and High Mid EQ boost/cut at the frequency set by the associated Freq knobs.
The Low Pass and High Pass filters are 12 dB per octave active filters with a smooth response in the pass band.
 
Outputs
The Line Level knob provides up to 10 dB of additional gain. The DI Level knob is a passive attenuator, ranging from unity gain to completely off. Both Line Out and DI signals are affected by Boost, Mute, and the stomp switches which toggle them on/off.
 
Tips and Other Info
 
Depending on how strong your incoming signal is, it may be advantageous to use low to moderate Gain to allow maximum headroom in the EQ section, and then boost the signal with the Line Out knob if needed.
 
With so much gain available, a compressor may be necessary to protect your equipment from large signal spikes that may be present on the attack of your signal. Peaks can easily go above 10V when using higher gain levels, which may cause other devices to distort. 
 
Typical electric bass and guitar signals need between 15 to 30 dB of overall boost to achieve line level, but this can vary dramatically depending on many aspects such as pickups, effects, string setup, and playing style, to name a few.
 
Gain in dB is additive. For instance, if you have Gain set for +15 dB, Boost set for +10 dB, and Line Level set for +10 dB, you have a total of +35 dB of gain. If you boost the Low EQ by another +15 dB, this means your low frequencies have a total of +50 dB of gain compared to your input signal.
 
Using the HPF to filter your ultra lows can allow more clean headroom, especially when using the Low EQ to boost your bass frequencies.
 
The LPF can filter out very high frequencies that may not be desired, such as string noise and fret buzz.
 
With the HPF at 25 Hz and the LPF at 20 kHz, they are effectively "off".
 
A simple approximation of a speaker cabinet's frequency response can be set up with the filters. A typical setting would be 100 Hz for the HPF and 5 kHz for the LPF, although you should experiement with different frequencies to find your desired tone.
 
A DI signal is often expected to be "instrument level" or "microphone level" in terms of signal strength. It is recommended you set the DI Level to -15 dB and adjust from there if needed.
 
When the Ground switch in pressed in, the Ground is connected to the XLR pin 1. This is the preferred setting. However, if using both the Line out and DI simultaneously, a buzz may occur in the audio signal due to a difference in ground potential between the connected equipment. In this case, lifting the Ground will isolate the grounds and reduce the buzz.
 
Dimensions
 
The messenger is 5.62" wide x 4.62" long