The Mackie MDB-1P is a passive direct box designed to connect a single instrument such as a guitar, bass, or keyboard to a microphone preamp for musicians and audio engineers in recording sessions, houses of worship, and live stage applications. It converts a high-impedance, instrument-level signal via its 1/4" TS unbalanced input to a low-impedance, mic-level output via its balanced XLR 3-pin jack. A 1/4" thru jack allows simultaneous connection to an amplifier or pedalboard.

A -15 dB pad reduces the input level to prevent distortion when using a high-gain source, and the ground-lift switch inhibits hum caused by ground loops. Due to its passive design, the MDB-1P requires no batteries or power supply. A sturdy steel chassis enables confident use in the studio or on the road.
Connect an instrument such as a guitar, bass, or keyboard to a microphone preamp
Converts a high-impedance, unbalanced 1/4" input to a low-impedance, balanced XLR mic-level output
1/4" thru jack for routing to an amplifier
-15 dB pad prevents overloading when accepting signal from a loud source
Ground-lift switch minimizes hum
Passive design requires no batteries or power supply

Mackie MDB-1P Specs
Type Passive
Input Connections 1 x 1/4" TS unbalanced
Output Connectors 1 x 1/4" TS unbalanced
1 x XLR 3-pin balanced
Input Impedance 140 kOhms unbalanced
Output Impedance 400 Ohms unbalanced
Impedance Ratio 350:1
Pad -15 dB
High-Pass Filter None
Controls Pad
Ground-lift switch
Frequency Response 20 Hz to 20 kHz (±0.2 dB)
Signal to Noise Ratio Not specified by manufacturer
Dynamic Range 128 dB
Total Harmonic Distortion 0.002% from 1 kHz
Power Requirement None
Current N/A
Construction Material Heavy-gauge steel chassis
Dimensions (H x W x D) 1.5 x 3.4 x 5.8" / 38 x 86 x 147 mm
Weight 0.8 lb / 0.4 kg