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Hughes & Kettner Red Box Pro

Hughes & Kettner Red Box Pro

The original Hughes & Kettner Red Box guitar DI used active circuitry to emulate the frequency response of a typical guitar cabinet and speaker, enabling guitars to be DI'd rather than miked while still retaining the tonal qualities of the amp or preamp they were played through. It worked very well, but now H&K have completely redesigned the unit using passive components to produce the Red Box Pro.

Housed in a red die‑cast metal case, the Red Box Pro can accept inputs at line level (preamp or pedal outputs), or it may be fed from speaker‑level signals. A selector switch is provided to choose between settings, as the speaker‑level option requires internal attenuation to match the levels. For connection, there's an unbalanced Input jack, and there's also a Thru jack allowing you to insert the device into the signal path. The Red Box Pro has no internal dummy load, so it's important, when you're using a guitar amp, that either the original speaker or a dummy load is connected to the Thru socket — especially so with valve amps, as running without a load can damage their output transformers.

A second slide switch selects between speaker simulator and a flat response, while a third switch functions as a ground lift. The output stage comprises a transformer, so input‑to‑output isolation is good. The passive filters used in the design have the benefit of shaping the sound, removing a lot of high‑frequency source noise, such as amp hiss or digital preamp grunge. However, these filters are lossy, and the output of the Red Box is designed to feed the mic input of a mixer, where the mic amp gain can be employed to restore the signal level. Another result of the passive system is that the noise performance is similar to that of a dynamic microphone, though it is also inevitably determined by the quality of the mic amp into which it is fed.

I tested the Red Box Pro with a number of sources, including a Line 6 Pod version 2 with its own speaker simulator turned off. The filter makes a good job of emulating a typical guitar cab, but obviously the result has to be a compromise, as there are no alternative settings for different speaker configurations. The unit has a slightly more 'American' sound than some of the other passive DIs on the market, with a little less bite, but also has the kind of high end you might expect from miking a guitar amp using a capacitor mic. As with any DI, you can always tweak the sound using your desk or preamp EQ if it's not completely your cup of tea — remember that a speaker‑simulating DI box like this is only one of the tools required to get a great guitar sound. Still, as a recording tool, the Red Box Pro is both simple and effective. Paul White