Behringer ADI21 Acoustic Guitar Preamp / DI Box with 3-Band EQ and Feedback Control

Acoustic guitarists often struggle to get a natural, balanced sound when plugging directly into a PA system or mixer. Piezo pickups can sound thin, harsh, and prone to feedback, while long cable runs degrade tone. The Behringer ADI21 solves these problems by combining a high-quality acoustic preamp with an active DI box in one rugged, stage-ready pedal. It delivers warm, studio-grade tone with flexible EQ and feedback suppression, ensuring your acoustic instrument sounds its best in any live or recording scenario.

Who is it for

The ADI21 is ideal for performing acoustic guitarists, singer-songwriters, and multi-instrumentalists who need reliable, transparent amplification. It is equally suited for home studios and live venues, providing a direct, noise-free connection to mixers, audio interfaces, or powered speakers. Whether you play a steel-string acoustic, nylon-string classical, or an acoustic-electric with a piezo pickup, this preamp will enhance your sound and eliminate common connectivity issues.

Main features

• Analog acoustic guitar preamp with active DI output (XLR balanced and 1/4" unbalanced)
• 3-band EQ with sweepable midrange (400 Hz – 1.6 kHz) for precise tone shaping
• Adjustable feedback filter to eliminate resonant frequencies and prevent howling
• Presence control for added sparkle and clarity
• Blend control to mix the direct signal with the processed signal
• Phase invert switch to correct phase issues when blending with a microphone
• Ground lift switch to eliminate hum from ground loops
• High input impedance (4.7 MΩ) preserves piezo pickup tone
• Rugged metal chassis with footswitch for on/off control
• Powered by 9V battery or optional DC adapter (Behringer PSU-SB recommended)

Specifications

• Input: 1 x 1/4" TS (instrument)
• Outputs: 1 x 1/4" TS (unbalanced), 1 x XLR (balanced DI)
• EQ: 3-band with sweepable mid (400 Hz – 1.6 kHz)
• Controls: Level, Bass, Mid, Treble, Presence, Feedback, Blend
• Input impedance: 4.7 MΩ
• Output impedance: XLR 600 Ω, 1/4" TS 1 kΩ
• Frequency response: 20 Hz – 20 kHz
• Signal-to-noise ratio: 90 dB
• Power: 9V battery (6LR61) or 9V DC adapter (not included)
• Current draw: 15 mA
• Housing: metal chassis
• Footswitch: on/off

Tips

For best results, place the ADI21 first in your signal chain, directly after your guitar. Use the blend control to balance the direct piezo signal with the preamp's processed tone. When using the XLR output to a PA system, engage the ground lift if you hear hum. To tame feedback, slowly sweep the feedback filter until the offending frequency is reduced, then fine-tune with the EQ. The phase invert switch is useful when combining the DI signal with a microphone on the same source.