MACKIE MDB-1A - Active DI box for instruments

MACKIE MDB-1A – Active DI box for instruments

The Mackie MDB-1A active DI is designed to provide exceptional headroom and distortion-free operation with active instruments such as guitars, basses, and keyboards with internal pickups or preamps. It features a high-impedance 1/4" input and “Thru” jack with a –20 dB pad to protect against high signal levels, and a Merge switch that converts the Thru output into a second input, ideal for summing stereo sources to a mono output. Its balanced XLR output features Polarity, Low Cut (120 Hz), and Ground Lift switches to eliminate unwanted noise. Powered by 48 V phantom power, it offers noise-free operation and is compact and rugged enough for live or studio use.

Main features

• Input: 1/4″ high impedance TS (330 kΩ unbalanced) with Thru jack and –20 dB pad.
• Merge: Switch that converts Thru into a second input for stereo sources.
• DI Output: Balanced XLR (150 Ω) with Ground Lift, Polarity and Low Cut (120 Hz).
• Frequency range: 20 Hz – 20 kHz ±0.5 dB.
• Distortion: THD ≤ 0.02% @ 1 kHz.
• Signal-to-Noise: 90 dB A-weighted.
• Power supply: Phantom 48 V (current < 4 mA).
• Construction: Compact “Built-Like-A-Tank™” metal chassis.
• Dimensions: 38 × 86 × 147 mm (H × W × D).
• Weight: 0.4 kg.

User benefits

• Extended Headroom: The –20 dB pad and active topology ensure distortion-free operation.
• Stereo to Mono Merge: The Merge switch makes it easy to inject stereo signals into a single channel.
• Noise Control: Low Cut and Ground Lift switches eliminate low-frequency hum and vibrations.
• Plug-and-play installation: Direct phantom power, no extra batteries or adapters required.
• Robustness: Metal construction to withstand intensive use on stage and in the studio.

Use cases

• Connecting active guitars, basses, and keyboards to consoles or microphone preamps.
• Summing stereo arrays (e.g. keyboards or media players) into mono PA.
• Recordings and live performances where low distortion and signal cleanliness are required.
• Fixed installations in studios, churches or conference rooms using instrument microphones.

Frequently Asked Questions

• Do I need phantom power? Yes; it runs exclusively on 48V phantom power.
• Can I use it with passive instruments? Yes, although the headroom and impedance will be optimized for an active source.
• How do I connect two stereo sources? Activate the Merge switch to use Thru as a second input and combine the two signals.
• Is the Low Cut fixed? Yes; it attenuates frequencies below 120 Hz to reduce rumble and ambient noise.

Description for projects

Mackie MDB-1A active DI: 1/4″ TS high impedance input with –20 dB pad and Merge, balanced XLR output with Ground Lift, Polarity, Low Cut 120 Hz, 48 V phantom, 20 Hz–20 kHz, THD ≤ 0.02%, metal chassis, 38×86×147 mm, 0.4 kg.