The Radial ProDI and ProD2 are passive direct boxes designed for converting high impedance instrument signals to low impedance balanced mic-level signals. This allows instruments like guitars, basses, keyboards, and drum machines to be connected directly to a PA or recording system without introducing noise, and to be driven through long cables to a mixing console. The ProDI is a single-channel device, while the ProD2 is a stereo two-channel device. Both are "plug & play" and do not require any external power, making them highly versatile for live sound and studio recording applications.
Function Description:
A direct box's primary function is impedance matching and signal balancing. The ProDI and ProD2 achieve this using high-quality, custom-designed impedance-matching transformers. This conversion is crucial because high impedance, unbalanced instrument signals are susceptible to noise and signal degradation over long cable runs. By converting the signal to a low impedance, balanced mic-level signal, the ProDI and ProD2 ensure clean signal transmission, similar to how microphones are handled in professional audio systems.
Typical applications include:
- Noise Elimination: By isolating the input signal from the output using a transformer, the ProDI and ProD2 effectively eliminate hum and buzz caused by ground loops.
- Signal Splitting: The THRU-PUT connector allows the instrument signal to be simultaneously sent to a stage amplifier while the balanced output goes to the mixer. For line-level sources, the THRU connector can feed a second mixer, recorder, or active monitor speaker.
- Unbalanced to Balanced Conversion: They convert unbalanced instrument signals to balanced mic-level signals, which are less prone to interference and can travel longer distances without degradation.
- Re-amping: The ProDI can be used in reverse to send pre-recorded signals to a guitar amp for re-amping effects.
Important Technical Specifications (ProDI and ProD2):
- Frequency Response: 20Hz to 20kHz +/- 2.5dB. This wide frequency response ensures accurate reproduction of the instrument's sound across the audible spectrum.
- Total Harmonic Distortion (THD): 0.01% from 20Hz to 20kHz. A very low THD indicates minimal signal coloration and high fidelity.
- Input Impedance: 140K ohms (with 1kHz input). This impedance is suitable for a wide range of instruments.
- Balanced Outputs: 150 ohms, -60dB mic level, pin-2 hot. The output impedance and level are designed to match typical microphone inputs on mixing consoles.
- PAD: -15dB. This attenuator helps prevent distortion when connecting ultra-high output sources.
Usage Features:
- 1/4" INPUT: Standard instrument input for connecting the source device.
- 1/4" THRU-PUT (ProDI) / LEFT & RIGHT 1/4" THRU-PUTS (ProD2): Parallel outputs for connecting the instrument signal to an amplifier, a second mixer, recorder, or active monitor speaker.
- -15dB PAD (ProDI) / LEFT & RIGHT -15dB PAD (ProD2): A switchable pad that reduces the input signal level by 15dB, preventing distortion from high-output instruments.
- XLR OUT (ProDI) / LEFT & RIGHT XLR OUT (ProD2): Balanced, low impedance mic-level outputs, wired with AES standard (pin-2 hot), for connection to a mixing console's microphone input.
- GROUND LIFT: A switch that disconnects pin-1 at the XLR output, used to eliminate hum and buzz caused by ground loops.
- Passive Design: No power required (no battery or phantom power needed), making it reliable and easy to deploy. Phantom power from a mixer will simply be ignored and blocked from reaching connected devices.
- Ease of Use: Designed for "plug & play" operation. Users are advised to set all volume levels to zero and turn off audio systems before connecting to avoid loud pops.
- Piezo Pickup Compatibility: While the ProDI works well with active piezo pickups (those with their own pre-amp and battery), passive piezo pickups (without a pre-amp) generally require a higher input impedance for optimal signal output. Radial's JDV and PZ-Pre products offer features specifically designed for passive piezo pickups.
Maintenance Features:
- BOOKEND DESIGN: The unique bookend cover design provides robust protection for the switches and connectors, enhancing durability in demanding environments.
- STEEL ENCLOSURE: An ultra-rigid I-beam design steel enclosure eliminates stress that could torque the PC board and cause solder joint failure, ensuring long-term reliability.
- FULL BOTTOM FOAM PAD: A foam pad on the bottom isolates the DI from the amp chassis and prevents it from sliding around on busy stages, protecting both the DI and other equipment.
- DOUBLE-SIDED PCB: Military-grade printed circuit board (PCB) with plated through-holes, bolted to welded steel standoffs, further enhances the structural integrity and reliability of the internal components.
- Radial Transformer: Custom-designed Radial transformers are integral to the outstanding audio performance and noise rejection capabilities of the ProDI and ProD2.
- 3-Year Transferable Warranty: Radial Engineering Ltd. provides a three-year transferable warranty against defects in material and workmanship, covering repair or replacement of defective components (excluding finish and normal wear and tear). This warranty underscores Radial's confidence in the product's build quality and longevity. To claim warranty service, the product must be returned prepaid in its original shipping container with a copy of the original invoice. The warranty does not cover damage due to abuse, misuse, misapplication, accident, or unauthorized service/modification.
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