High-performance direct box offers pristine sound for the studio
From the November/December 2020 issue of Acoustic Guitar | By Doug Young
Acoustic guitar pickups offer convenience when recording, but often produce thin, sterile tones. To address the issue, Radial, known for making high-quality direct boxes for stage use, has introduced the HDI High Definition Studio DI, a unique tone-shaping tool for guitars as well as other instruments.
The HDI is most at home in the studio, with a solidly built, AC-powered, two-space half-rack design. The active DI has a clean front panel that features a VU meter; Level, Color, and Presence controls; switches for high pass filter; input impedance selection; and an optical compressor. A power switch and 1/4-inch input jack, as well as a 1/4-inch through output jack and ground lift, complete the front-panel controls. The back panel has XLR outputs for both mic and line level—capable of delivering up to +25dBu—as well as a 1/4-inch output and additional input jacks.
The key to the HDI’s sound is its two parallel signal paths, one clean, the other heavily colored. Both paths incorporate a high-quality Jensen transformer, but the clean path uses negative feedback to produce a very linear response, while the colored path emphasizes the saturation potential of the transformer and adds a tube-like tone. The Color knob controls the balance between the two paths.
The clean path supports an optical compressor with two compression thresholds. The Presence control adds a high frequency boost, while engaging the high-pass filter switch rolls off lows below 40Hz or 100Hz. You can also choose between an input impedance of 200K or 2M ohms.
I found the HDI to have a robust sound and a very useful range of colors that should enhance any guitar pickup. The Color control makes it possible to dial in anything from a clean but warm tone to crunch-style distortion. When triggered with more aggressive strumming, the optical compressor pleasantly smooths out the sound of the clean path. The Presence control can add just a touch of clarity to the sound, or a strong shimmer that would make a rhythm acoustic guitar pop in a mix. Together, these controls—which interact to some degree—offer a rich set of tonal options to beef up the sound of a pickup. While the HDI produces excellent tone with any setting, I leaned toward the middle range of the Color control, exploring subtle changes that leveraged both signal paths.
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The HDI’s form factor might be optimized for the studio, but it would be a welcome addition to a stage rig as well, and its multiple outputs provide flexible routing and interesting options for live sound. With a street price of $799.99, the HDI is an impressive, professional-quality piece of gear for the money.