The DOD Direct Box is a series of audio interface devices designed to address distortion issues commonly encountered when connecting high-impedance sources to low-impedance inputs. The product line includes the AC 260, AC 265, AC 275, and AC 285, each offering a progressive set of features, with the AC 285 incorporating a cabinet emulator.

AC 260 Direct Box

Function Description: The AC 260 is a basic, easy-to-use direct box that allows a high-impedance unbalanced source to directly feed a low-impedance balanced input. It is designed to minimize distortion and noise in audio signals.

Important Technical Specifications:

Low Impedance In/Output: 600 ohms center tapped (balanced).
Low Impedance Connector: XLR type jack.
High Impedance In/Outputs: 50KΩ.
High Impedance Connectors: 2 - 1/4" mono phone jacks.
Frequency Response: Not specified in the provided text.

Usage Features:

Connect the output of the high-impedance source to the input of the AC 260.
Connect the low-impedance output of the AC 260 to a mixing console or other low-impedance input.
Connect the unbalanced 1/4" tip-sleeve output to a high-impedance input.

Maintenance Features:

Rugged metal chassis for durability.

AC 265 Direct Box

Function Description: The AC 265 builds upon the AC 260 by offering more versatile impedance matching capabilities and additional features for signal integrity. It connects high impedance (50K ohms) to low impedance (600 ohms), or low impedance to high impedance. It also includes a ground lift switch to mitigate ground-loop hum problems and an adjustable attenuation pad.

Important Technical Specifications:

Low Impedance In/Output: 600 ohms center tapped (balanced).
Low Impedance Connector: XLR type jack.
High Impedance In/Outputs: 50K ohms (unbalanced).
High Impedance Connectors: 2 - 1/4 inch mono phone jacks.
Attenuation Range Switch: 0, 12, 40 dB attenuation.
Frequency Response: 60 to 15 kHz, ±3 dB.

Usage Features:

Connect the output of the high-impedance source to the input of the AC 265.
Connect the low-impedance output of the AC 265 to a mixing console or other low-impedance input.
Connect the unbalanced 1/4" tip-sleeve output to a high-impedance input (if desired).
Set the ground lift switch to the position with the least amount of hum or noise.

Maintenance Features:

Rugged metal chassis (implied, as it's a progression from AC 260).

AC 275 Active Direct Box

Function Description: The AC 275 is an active direct box designed for connecting guitar pickups, microphones, or electric instruments to a recording or P.A. console without audio quality loss. It utilizes FET input operational amplifiers for input signal isolation, reducing loading effects commonly found in passive direct boxes. It operates with either battery or phantom power and offers internal padding for speaker-level inputs.

Important Technical Specifications:

Frequency Response: 20Hz-20kHz, ±0.5dB.
Gain: Inst: -12dBu, Spkr: -40dBu.
Input Impedance: Instrument 1.3MΩ, Speaker 10KΩ.
Output Impedance: 200Ω.
Power Requirements: 9V battery or 15-48V phantom power.
Distortion (1kHz, Inst @-10dBV input): <0.02%.
Signal-to-Noise Ratio (Inst @-10dBV input): Better than 86dB.
Maximum Input (Instrument Position): +7dBu (9V battery), +5dBu (15V phantom), +20dBu (48V phantom).
Supply Current: 4mA (9V battery), 4mA (15V phantom), 8mA (48V phantom).
Input Connector: 1/4" tip-sleeve.
Output Connector: XLR, 1/4" tip-sleeve.
Dimensions: 2.5"x4.5"x1.5".
Weight: 15oz (422g).

Usage Features:

Connect the output of the high-impedance source to the input of the AC 275.
Connect the low-impedance output of the AC 275 to a mixing console or other low-impedance input.
The unbalanced 1/4" tip-sleeve output is hard-wired to the input and can be connected to a high-impedance input if desired.
Set the ground lift switch to the position with the least amount of hum or noise.
Set the pad switch to INSTRUMENT for line-level input sources or to SPEAKER for speaker-level input sources.
Set the power selector switch to ON for battery power or to OFF for phantom power.

Maintenance Features:

To preserve battery life, set the power selector switch to OFF when the AC 275 is not in use.

AC 285 Direct Box

Function Description: The AC 285 is the most advanced direct box in the series, incorporating all the features of the AC 275, including FET input operational amplifiers for signal isolation and flat frequency response. Additionally, it features a cabinet emulator with two settings: a 4x12 emulator cabinet for an enhanced low end and a twin open-back combo for a brighter sound with less low end. It allows a high-impedance unbalanced source to directly feed a low-impedance balanced input, connecting various instruments to a console without audio quality loss.

Important Technical Specifications:

Frequency Response: 20-18 kHz ±1dB (Flat), 10-30 kHz ±3dB (Emulation).
Gain: Instr: -12dB, Spkr: -40dB.
Input Impedance: Inst: > 1 megΩ, Spkr: >200 KΩ.
Output Impedance: 200Ω.
Power Requirements: 9V Battery, 15-48V Phantom, 9V AC Adapter (DOD PS3).
THD (1kHz, Inst @ 0dBu, 9V batt): <0.08%.
Signal to Noise Ratio (Inst @ -10dBu, 9V): Flat: >86dB, Spkr Emulation: >80dB.
Maximum Input Level (Inst): 7dBu (9V battery or adapter), 5dBu (15V Phantom), 20dBu (48V Phantom).
Supply Current: 8 mA (9V battery), 16 mA (48V Phantom).

Usage Features:

Connect the output of the high-impedance source to the input of the AC 285.
Connect the low-impedance output of the AC 285 to a mixing console or other low-impedance input.
Connect the unbalanced 1/4" tip-sleeve output to a high-impedance input (if desired).
Set the ground lift switch to the position with the least amount of hum or noise.
Set the pad switch to INSTRUMENT for line-level input sources or to SPEAKER for speaker-level input sources.
Set the power selector switch to ON for battery power or to OFF for phantom power.
Set speaker settings to FLAT for a direct-to-microphone sound. For a guitar-to-board sound, use the 4x12 or COMBO settings.

Maintenance Features:

To preserve battery life, set the power selector switch to OFF when the AC 285 is not in use.

All models are designed to solve distortion problems associated with using high-impedance sources with low-impedance inputs, providing clean and reliable audio signal conversion.

DOD AC 265 - Page 9

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