How to Use Direct Box to Hook a Keyboard to a Laptop
Before using a direct box to hook a keyboard to a laptop for recording, an understanding of direct boxes and input signals is necessary for best sound quality and prevention of sound card damage. Standard laptop sound cards are designed to accept high impedance mic-level inputs, but electronic keyboards emit stronger high impedance line-level signals. A Direct box -- also known as a "DI" for "direct injection" -- are used in pro audio applications to step line-level voltage down to mic-level and convert high impedance inputs to low impedance inputs. Plugging a low impedance input into the computer's high impedance input will result in volume loss, but can be solved with the addition of an impedance matching transformer and interconnect cable between the DI and computer.
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Things You'll Need
- Standard musical instrument interconnect cable with dual 1/4-inch TS male phone plugs
- Standard microphone cable with XLR male and female plugs
- Microphone impedance matching transformer with integrated female XLR input and 1/4-inch TS male output plug
- Shielded interconnect cable with 1/4-inch female TS phone jack terminating to 1/8-inch male TS mini plug.
Instructions
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Connect the keyboard to the direct box by inserting one of the 1/4-inch male plugs of the interconnect cable into the keyboard output jack and the other plug into the direct box's 1/4-inch input jack.
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Insert the female XLR plug of the microphone cable into the DI's XLR male output jack.
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3
Plug the impedance matching transformer's integrated female XLR plug into the microphone cable's male XLR jack.
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4
Insert the impedance matching transformer's integrated 1/4-inch male TS plug into the 1/4-inch female jack of the second interconnect cable.
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Plug the 1/8-inch TS male mini plug of the second interconnect cable into the laptop's microphone jack.
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Turn on the keyboard's power switch and start the computer's recording program to test for operation. Follow your program's tutorial or consult the help menu for arming tracks and setting input recording levels.
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Tips & Warnings
USB or Firewire audio interfaces are used by home and professional recording engineers. Interfaces provide improved sound quality by bypassing computer sound cards and do not require an impedance matching transformer.
The use of an active or passive direct box is contingent upon keyboard type and output signal strength, but both types connect in the same manner.
Some models of impedance matching transformers use an integrated female 1/4-inch output jack rather than a male plug. This type will require a 1/4-inch TS male plug on the computer interconnect cable instead of a 1/4-inch female plug.
When testing for operation, keep keyboard and recording program input volumes at low settings -- gradually increasing each volume until desired levels are reached. High volume levels from either source will result in distortion and may cause damage to the computer sound card.
References
Resources
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