DI-3 and DI-2

  Active Direct Injection Boxes - User Guide

MTR's Active Direct Injection Boxes take a signal from an instrument (guitar, bass, keyboard, etc.) and, by presenting a very high impedance to the instrument and balancing the output, prepares it for direct connection without level or frequency losses to a mixing console in the studio or live on stage.

Connections: Connect the instrument to the jack socket marked Input, using a mono jack plug. This socket switches the battery on and off, so remove the jack plug after use. If needed, a second mono jack-to-jack lead can be connected from the Link socket to the input of a combo, so that the musician can monitor himself on stage or in the studio.

The balanced XLR Output socket (pin 2 hot) should be connected via a balanced 2 core screened lead to the stage box, or input socket of the mixer.

Ground: The Ground switch is used to eliminate hum loops. Start with the switch in the 'GND' position, and if hum occurs due to an earth loop with the combo or mixer, switch to 'LIFT'.

Attenuator: The 3 way attenuator allows accurate input level matching: start at 0dB and decrease to -20 or -40 if distortion occurs. Use the -40dB setting for speaker outputs from, for example, guitar amps.

Power: Both models run on an internal 9 volt battery (not supplied), accessed by removing the lid. If the console can supply phantom power, this can be used to run the unit just by connecting the Output socket to a mic input of the mixer, up to a maximum of 48v. It is not necessary to remove the battery, but, if a battery is not fitted, we recommend that the plastic sleeve supplied is left over the battery terminal clip to prevent possible shorting. The DC input can also be used to connect an external 9 volt DC supply, this should be a regulated model to avoid hum.

CAUTION: observe the polarity diagram on the lid: centre pin negative, outer ring positive.

The DI-2 two channel version is literally two DI-3's in one box, for stereo keyboards or simply two mono channels. All the above applies, plus: only channel 1 will accept phantom power (to prevent two feeds of phantom power entering), but this will supply power to both channels. If only 1 channel is needed, use channel 1 rather than 2. This is because, in order to allow the battery low led to work on both channels, channel 2 will not work without a jack plug inserted into the Input socket of channel 1. When both channels are used, the ground lift should be in the same position on each channel.

Specifications

Frequency response: 20Hz-20KHz ± 1.5dB                           Input impedance:   1Mohm, jack + jack link
Output Impedance:    600W, bal. XLR, pin 2 hot                   Attenuation switch:  -40dB, -20dB, 0dB
Signal/Noise:  -103dBu                                                      DC input:  9v, 100mA, neg. centre pin
T.H.D:  0.005 @ 1KHz                                                        Low battery led:  Indicates @ approx. 4.5v

MTR Ltd, Ford House, 58 Cross Rd, Bushey, Herts, WD19 4DQ   UK
Tel: +44-(0)1923-234050   Fax: -255746    e-mail: mtrltd@aol.com    www.mtraudio.com