Topic summary
Direct box
Extracted from the Wikipedia article DI unit.
History
The passive direct box was suitable for most electronic musical instruments but it negatively colored the sound of instruments with weaker output signals, such as Fender Rhodes pianos and Fender Precision Basses with single-coil pickups. To accommodate these instruments, active direct boxes were designed containing powered electronic circuitry which increased the input impedance to above 1,000,000 ohms. In 1975, a 48-volt phantom powered active direct box was designed for Leon Russell's recording studio, its circuitry published in the April 1975 edition of dB, the sound engineering magazine. The sound company Tycobrahe, known for supporting large rock festivals such as California Jam, offered an active direct box for sale in 1977 capable of +9 dBm line level output with a built-in attenuator to compensate for various input levels.