DI Box for Acoustic Guitar: Amplifying Natural Tone

A DI box for acoustic guitar bridges the gap between the instrument’s pickup system and the PA. Acoustic guitars present unique challenges—piezo pickups with peculiar impedance characteristics, feedback susceptibility, and the goal of reproducing natural acoustic tone through electronic amplification.

Piezo Pickup Challenges

Most acoustic guitars use under-saddle piezo pickups that present extremely high impedance to following electronics. This impedance can exceed 1 megohm at certain frequencies, creating loading problems with standard DI boxes.

Piezo pickups loaded by insufficient input impedance exhibit characteristic “quacky” or thin tone with excessive midrange emphasis. The fundamental fullness disappears, replaced by unpleasant coloration.

Active DI boxes with very high input impedance (1-10 megohms) suit piezo pickups much better than passive alternatives. The high impedance prevents loading, preserving the pickup’s intended frequency response.

Some acoustic guitars include onboard preamps that buffer the piezo signal. These buffered outputs present lower impedance that passive DIs can handle, though active DIs still work well.

Magnetic Soundhole Pickups

Magnetic pickups in acoustic guitars behave similarly to electric guitar pickups. These passive magnetic elements benefit from active DIs with high input impedance.

Magnetic pickups provide different tonal character than piezo—more like an electric guitar, less like a miked acoustic. Some players prefer this character; others find it insufficiently “acoustic.”

Blending magnetic and piezo pickups combines the best of both. Dual-source systems require either two DI channels or specialized blending units.

Specialized Acoustic DI Options

The LR Baggs Para DI combines DI functionality with 5-band EQ and adjustable notch filter for feedback control. This popular unit specifically addresses acoustic guitar needs.

The Radial PZ-Pre provides high input impedance, EQ, and blend capability for dual-pickup systems. The phase switch addresses phase issues between multiple sources.

The Fishman Aura series combines DI with imaging technology that matches the processed pickup signal to specific microphone characteristics, improving perceived naturalness.

The Grace Design ALiX provides audiophile-grade preamp and DI functionality with exceptional transparency and headroom.

Feedback Control Features

Acoustic guitars amplified through PA systems are prone to feedback, especially when stage volume is high or when monitors point toward the guitar body.

Notch filters on acoustic DIs allow cutting the specific frequency causing feedback without affecting the overall tone significantly. Sweepable notch filters are more effective than fixed-frequency alternatives.

Phase switches can sometimes reduce feedback by changing the reinforcement/cancellation relationship at problematic frequencies. Experimenting with phase often improves feedback stability.

High-pass filters reduce low-frequency feedback and rumble without affecting the guitar’s useful frequency range. Filtering below 80-100 Hz typically helps without obvious tonal impact.

Tone Shaping Capabilities

EQ on acoustic DIs enables tone adjustment before the signal reaches the mixer. Addressing pickup characteristics at the source provides cleaner signal to the PA.

Common adjustments include reducing piezo harshness in the 2-4 kHz range, adding warmth in the 200-400 Hz range, and controlling extreme highs that piezo pickups can emphasize.

The goal is natural acoustic tone—what the guitar sounds like when played unamplified. Pickup systems rarely achieve this naturally; EQ helps bridge the gap.

Active vs Passive Selection

Active DIs are almost always preferable for acoustic guitar. The impedance requirements of piezo pickups, combined with the benefits of onboard EQ and features, favor active designs.

Passive DIs might work for acoustic guitars with onboard preamps that already buffer the signal and provide their own EQ. But active DIs designed for acoustic guitar offer more relevant features.

Battery operation versus phantom power affects reliability differently. Phantom power eliminates battery concerns but requires mixer support. Batteries provide independence but add a failure point.

Integration with Guitar’s Onboard Controls

Many acoustic guitars include onboard preamps with volume and EQ controls. These controls affect the signal before it reaches the DI.

Coordinating onboard guitar EQ with DI processing prevents over-correction or conflicting adjustments. A flat setting on one allows full control from the other.

Volume controls on the guitar affect DI input level. Consistent guitar volume settings produce predictable results from the DI and mixer.

Placement and Connection

Position the DI near the performer for short cable run from guitar to DI. Short unbalanced cable minimizes noise pickup; long balanced run from DI to mixer rejects noise.

The through output on many DIs enables connection to an acoustic amplifier while sending DI signal to the mixer. This setup serves performers who want personal acoustic amp monitoring.

Secure cable connections prevent intermittent dropout during performance. Acoustic guitarists often move while playing; connections must survive this movement.

Achieving Natural Sound

The ultimate goal is making the amplified acoustic guitar sound like an acoustic guitar—not like an electric guitar or a synthesized approximation.

This requires appropriate DI selection, careful EQ, and often compromise. Perfect reproduction of acoustic guitar through PA systems remains elusive; minimizing the gap is the practical goal.

Working with the performer to understand their tone expectations guides the approach. Some players accept departure from acoustic tone; others require closer approximation regardless of technical challenge.