EarthQuaker Devices ZEQD PRE - Tube Preamp / Booster / Di Box

A collaboration between EarthQuaker Devices and Dr. Z Amplification

This all-analog tube preamplifier brings together EarthQuaker Devices’ innovative pedal design and Dr. Z Amplification’s decades of tube amp expertise. With a passive three-band EQ, professional headphone output, balanced XLR output, and onboard analog cabinet simulation, the ZEQD-Pre delivers authentic tube warmth and dynamic response in a complete analog amplifier system that fits right on your pedalboard.

More than an Amp:

Practice Amp with Headphones
The headphone output features built-in analog cabinet simulation for a realistic amp feel during quiet practice sessions. Enjoy the full EF86 tube character without disturbing your housemates.

Direct Amplifier via XLR
Run the balanced XLR output straight into any console or interface and use the ZEQD-Pre as your main amp. The analog cabinet simulation is there when you need it, or flip the Cab Bypass switch to send a pure signal to your preferred IR loader or modeling software. Perfect for direct recording, backline-free gigs, or hybrid rigs with multiple signal paths.

Flexible Routing
All outputs work simultaneously, even when the pedal is bypassed. Send your signal to an amp, route a direct feed to front-of-house, and monitor through headphones—all at once. This routing flexibility makes the ZEQD-Pre an invaluable studio tool.

Why The EF86 Tube?

The ZEQD-Pre uses the EF86 pentode—the same tube that gives many Dr. Z amplifiers their pristine hi-fi tone and makes them such responsive pedal platforms.

The Technical Side

Unlike the common 12AX7 triode (two elements plus cathode), the EF86 pentode has four internal elements plus cathode. This structure yields measurably superior performance:

Gain Factor of 185: Significantly higher than comparable triodes

44V RMS Output: Substantial voltage swing for enhanced dynamics

Extended Frequency Response: Full-spectrum clarity from deep lows to detailed highs

What This Means for You

These specifications translate directly to playing experience:

Touch Sensitivity: The EF86 responds to every dynamic nuance in your playing. Play lighter and it cleans up; dig in and it blooms. Natural expression that follows your hands.

Full-Frequency Clarity: Extended response means harmonic richness without sacrificing definition. Bass notes stay tight, highs remain bell-like and clear.

Responsive EQ: Higher voltage and broader bandwidth let the passive Three-Band EQ shape your tone effectively with minimal signal loss. The interactive controls behave like classic tube amp tone stacks—predictable and musical across their entire sweep.

The EF86 brings hi-fi performance to tube preamplification while staying responsive and musical.

Controls:

Boost: Use the Boost rotary knob for volume control when the Boost is active and the tone controls are bypassed. Boost mode is very loud! Be careful when setting the Boost level, especially when using headphones or XLR out.

Boost Footswitch: This footswitch defeats the tone controls and delivers a full-range boost without altering the frequency response. This switch is only active when the Activate footswitch is on.

Headphone Output: A TRS (Stereo) ¼” headphone jack is located on the left side. Use the Level control to adjust headphone level when the pedal is active. The headphone output works as a unity gain amplifier with cabinet simulation even when the pedal is bypassed.

Direct Output: A balanced XLR output is located on the left side of the pedal.

Ground Lift Switch: Press this switch on the left side of the pedal for ground lift on the XLR output.

Cab Sim Bypass Switch: Press this switch on the left side of the pedal to remove the analog cabinet simulation on the XLR output.

Level: Use the Level rotary knob to adjust the output volume when the tone controls are active.

Bass: Use the Bass rotary knob to adjust the frequency range from 20 Hz to 400 Hz.

Middle: Use the Middle rotary knob to adjust the frequency range from 400 Hz to 2 kHz.

Treble: Use the Treble rotary knob to adjust the frequency range from 2 kHz to 20 kHz.

Activate Footswitch: Use this footswitch to activate or bypass the ZEQD-Pre.

Tech Specs:

Dimensions 5.88 x 3.94 x 2.75 in. (149 x 100 x 70 mm) with knobs

Current Draw 500 mA

Input Impedance 10 MΩ

Output Impedance Variable

Headphone Out Impedance 39 Ω

Direct Out Impedance 100 Ω

Switching ZEQD-Pre uses mechanical true bypass switching.

Power

This device takes a standard 500 mA (or higher) 9-volt DC power supply with a 2.1 mm negative-center barrel. We always recommend pedal-specific, transformer-isolated wall-wart power supplies or multiple isolated-output supplies. Pedals will make extra noise if there is ripple or unclean power. Switching-type power supplies, daisy chains, and non-pedal specific power supplies do not filter dirty power as well and let through unwanted noise. DO NOT RUN AT HIGHER VOLTAGES!