Radial HDI Direct Box


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Product Code: 2770
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The Radial HDI Direct Box is a high-end studio-quality direct box designed to create exceptional recordings with any instrument. Utilizing premium Jensen transformers and a unique color control that provides an entirely new, yet familiar-sounding, the HDI is a "must have" for any studio!

Despite the complex circuitry housed within the unit, the HDI has an elegant set of controls that allows the musician or engineer to dial up a record-ready sound with a minimal amount of tweaking required. The Level control drives the inputs of the HDI with instant visual feedback from the responsive front panel meter, while the Color knob provides seamless blending between an ultra-clean tone and amp-style distortion and saturation, so you can add just the right amount of character and grit to your instrument. A smooth Opto compressor can be engaged to control the peaks of the input signal, and a High-Pass Filter clears up any excessive low frequencies added by the Color control. Lastly, a Presence control accentuates the highs and high-mids, providing the ability to cut through the mix with results that are sure to impress.

Looks and Personality
With its gunmetal anodized 1/4" thick milled front panel and distinctive styling reminiscent of classic outboard studio equipment, the HDI is sure to turn heads in any recording space. A custom output meter provides a level check at a glance, with oversized chrome knobs for precise adjustments and easy tweaking on-the-fly. The HDI is a stunning standalone unit, but it also comes complete with mounting hardware to install in standard 19" equipment racks. One or two HDI's can be installed side-by-side in a 2RU rack space, and like all Radial products, they are built with rugged components and designed to easily withstand the rigors of concert touring.

Behind the Design
While the HDI is incredibly easy to use - requiring only a few seconds to achieve great-sounding results - both the design philosophy and the under-the-hood processes at work are anything but simple. Click here to read an interview with the HDI's designer, W.C. "Hutch" Hutchison for an in-depth look at how the HDI came to be and what makes its circuitry so unique.

Radial HDI Direct Box Features

  • Dial in an amazing tone within seconds
  • Blend from ultra-clean to amp-like distortion
  • Smooth Opto compressor for peak reduction
  • Mic and line-level outputs
  • Oversized custom-wound Jensen transformer

Radial HDI Direct Box Specifications

  • Frequency response: Line Output: 1Hz ~ 100kHz +0.25/-3dB, 20Hz ~ 20kHz +/-0.1dB Mic Output: 1Hz ~ 100kHz +0.25/-3dB, 20Hz ~ 20kHz +/-0.1dB
  • Dynamic range: 112dB (20-20k, unweighted, referred to +25dBu)
  • Gain: Min Gain (Level CCW): -3dB Max Gain (Level CW): +31dB
  • Total harmonic distortion: 0.3% @20Hz, 0.22% @100Hz, 0.01% @1kHz (+4dBu In)
  • Signal to Noise: 91dB (20-20k, unweighted, referred to +4dBu)
  • Maximum Input: 1/4" TS: +5dBu, 3 VAC RMS, 8.4 V Peak to Peak 3.5mm: +25dBu, 7 VAC RMS, 20V Peak to Peak (Level @ 12:00)
  • Maximum Output: Line Level XLR: +25dBu (1% THD at 1kHz) Mic Level XLR: +3.7dBu (1% THD at 1kHz) 1/4"
  • Processed Out: +8dBu (Approx. unity gain with Level @ 12:00)
  • Input Connectors: 1/4” TS (front and rear), 3.5mm Synth
  • Output Connectors: XLR Line / Mic, 1/4” TS Processed, 1/4” TS Thru
  • Construction: 14 gauge steel chassis, 1/2” aluminum front panel
  • Size (L x W x D): 8.25” x 8.25” x 3.5”
  • Weight: 5.05lbs
  • Power: 100-200VAC 0.45A ~ 50/60Hz

Radial HDI Direct Box Includes

  • Radial HDI Direct Box
  • Power Cable
  • Rackmount Kit
  • Owner's Manual
  • Manufacurer Warranty

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What We Think


The Radial HDI is my favorite direct box for recording bass guitar. It’s ability to go from ultra-clean to warm and saturated, all the way to amp-like distorted makes the HDI super versatile. The color knob helps get some character and mojo into your signal thanks to the Jensen transformers. I love the way the single-color knob fattens up a signal and gives some color with a nice mid-range push. The presence knob is so smooth and really helps to lift the top-end and get some pick or finger attack on guitars and bass. You also have two styles of optical compression! This is super helpful especially when recording bass guitar. Having a high-pass filter on the unit is a nice tough as well. The HDI has some nice I/O options including a thru output for splitting the signal allowing you to go into an amplifier or a separate DI. It also features a processed output that allows you to get all the color and compression from the HDI and then feed that signal into another amplifier and use the HDI ass a pre-preamp. The HDI is an impressive and high-quality studio direct box and I highly recommend it!

Wes DeLoach, Pro Audio Sales

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