AEA TDI is a single-channel active DI box powered by 48 V phantom power, designed by Fred Forssell. Built around a discrete Class A JFET stage and a Lehle step-down transformer, it converts unbalanced Hi-Z instrument signals to balanced mic level with no tonal coloration and no dynamic compression.
10 MΩ Input — Preserving Passive Pickup Character
Passive pickups are designed to work into a high-impedance load. The TDI presents 10 MΩ at its input, giving the transducer the conditions it needs to reproduce its full tonal range — presence, attack, and natural decay intact. For piezo-equipped acoustic-electrics, this removes the brittle, nasal quality that appears when the pickup is loaded by a standard 1 MΩ or lower input. The JFET buffers the signal before it reaches the transformer winding, keeping noise and THD at the floor across cable runs well beyond 30 meters. Measured noise floor is better than –114 dBu (22 Hz–22 kHz, unweighted).
–20 dB Pad, Ground Lift and THRU Jack
The –20 dB pad extends the TDI's usable range beyond passive instruments — speaker-level outputs from combos, synth lines, and samplers all connect without an external attenuator. The THRU jack runs in parallel with the input and does not load the signal path: you can feed both the DI and a stage amp simultaneously, keeping full wet/dry control during tracking. The ground lift switch breaks ground loops without interrupting signal flow — essential on stages with multiple independently powered devices. The steel chassis includes rack-mount screw holes; three TDI units mount into a single 1U rack space.
KEY FEATURES
- Single-channel active DI, 48 V phantom-powered
- Discrete Class A JFET stage + Lehle step-down transformer
- Input impedance: 10 MΩ (instrument) / 55 kΩ (pad engaged)
- –20 dB pad — handles speaker-level and active line-level signals
- Parallel THRU jack for simultaneous amp feed
- Ground lift switch
- Noise floor: better than –114 dBu (22 Hz–22 kHz, unweighted)
- Steel chassis — 3 units mount in 1U rack space
- Circuit design: Fred Forssell; made in the USA
TECHNICAL SPECIFICATIONS
- Channels: 1
- Type: active DI, phantom-powered
- Input impedance: 10 MΩ (instrument) / 55 kΩ (–20 dB pad)
- Pad: –20 dB (switchable)
- Ground lift: yes
- Input connectors: 1/4" jack (INPUT) + 1/4" jack (THRU)
- Output connector: XLR (balanced)
- Power: 48 V phantom power
- Noise floor: better than –114 dBu (22 Hz–22 kHz, unweighted)
- Dimensions: 129 × 76 × 51 mm
- Weight: 0.4 kg
- Made in: USA
