Road Test Underway: Switchcraft SC800 Instrument Direct (DI) Box

Active DIs can be a good choice for matching the lower signals provided by passive instrument pickups.

However, many acoustic guitars and electric basses have on-board active electronics (“battery inside?”), making a passive DI a good match for their higher output levels.

Other applications include electronic keyboards, and various “Prosumer” line level playback devices with unbalanced outputs.

The connectors and switches on each end – which of course are all Switchcraft – are on anodized cerulean blue panels, recessed to protect their “short handle” pad and ground-lift switches.

One end has the usual pair of quarter-inch TS jacks for signal input and through-patching, with a 20 dB pad switch between. The other end has a male XLR and a pin 1 lift switch, plus a second quarter-inch through jack. The SC800’s rugged industrial design is an instant classic.

The specifications match the Jensen transformer inside, like the common mode rejection listed as greater than 100 dB at 60. Input impedance is greater than 150,000 Ohms at 1,000 Hz and output impedance is less than 170 Ohm.

Back panel view of the SC800. (Click to enlarge)

Stated phase response is less than 3 degrees at 20 Hz, less than 1 degree at 1,000 Hz and less than 16 degrees at 20,000 Hz. With a +4 dBu input (1.23 volts RMS), Total Harmonic Distortion (THD) is less than 0.05 percent at 20 Hz and less than 0.006 percent at 1,000 Hz.

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It has a maximum input level of +21 dBu, or 8.7 volts, which is where THD at 20 Hz rises to 1 percent. With the 20 dB pad engaged it will take a +41 dBu signal, enough for most small guitar amps if there’s also a speaker or resistive load attached.

Stated frequency response is 10 Hz to 40 kHz, plus or minus 0.3 dB, and stated voltage gain is minus 23 dB, or minus 43 dB with the 20 dB pad engaged.

Finally, the SC800 is hand-built in Chicago, Illinois.

Next I’ll take it to a few shows and try it on stage with a variety of audio inputs…

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Mark Frink is a long-time audio professional and is also associate editor of Live Sound International magazine.

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