Professional Audio

DI-3 and DI-2 Active D.I. Boxes / Balanced Splitter



Cost effective but high quality quality direct boxes are hard to find in today’s disposable marketplace – top quality products are too expensive, or the economy version is way too unreliable, noisy, and fragile.

MTR DI-3 Active Direct Injection BoxThe MTR DI-3 single channel D.I. box changes all that.   It has a mono jack input, and link out socket to, for instance, an on stage or in studio combo, a ground lift to eliminate hum loops, a three position attenuator for accurate level matching, and a balanced 600 ohm XLR output.   The active electronics have a purely resistive high input impedance, and so do not colour the sound.

MTR DI-2 Two Channel Active D.I. BoxThe DI-2 is a two channel version in the same sized box, for use with stereo keyboards or two separate mono signals.  It can also be used as a balanced signal splitter by connecting a short jack-to-jack lead from the link socket of channel 1 to the input of channel 2.  Channel 1’s signal will then be available on both balanced XLR’s, and channel 2’s link socket.  The attenuation switches remain working independently.

Both models can be powered in 3 different ways: by a 9 volt PP3 battery, phantom power up to 48v from the desk (or an MTR PPS-48), or an external 9v regulated power supply into the DC socket on the left edge.


  • Frequency response:  20Hz-20kHz ±1.5dB.
  • Distortion:  (THD) < 0.005% at 1kHz, 0dBu
  • Output noise:  <-100dB unweighted
  • In/Link impedance:  1MOhm, jack.
  • Output impedance:  600 Ohms balanced XLR.
  • Attenuation switch:  -40dB, -20dB, 0dB.
  • Ground Switch:  lifted/connected.
  • DC Input:  9vDC, 100mA, neg. centre pin
  • Phantom Power:  +18 volts DC to +48 volts DC
  • ‘Low Battery’ led:  glows @ approx. 6v

User Comments:

“I have a number of the MTR active DI’s, and the newest of them has given over 6 years trouble free service – the oldest is nearer 20”

– Peter John Chivers

“Another happy user of MTR active DIs.   Note these DIs do not have transformers in them, so they have an interesting set of tradeoffs; they have extended frequency response compared to lesser transformer equipped DIs, so bass gtr is not a problem. It also means they never truly ground lift, and it means they never get inductive coupling from the mains or output transformers of the amp they are sitting on.  All that said, in practice, they work, and work well”.

– David Buckley.

“Thanks for a couple of excellent pieces of kit: just got two D1-2s to add to my DI-3: a 15-year old veteran that is still going strong! “

– Mike Willoughby – melodeon, bouzouki, guitar, harmonica with Ceilidh band Striding Edge,

“I have been using MTR DI boxes for over 10 years now with flawless performance and these dual passive ones are no exception.  I have always found them to be well built.  You get the feeling you could drop them from a lighting rig and they’d still work.  The sound quality is also very good. The features are very user friendly with a ground lift, a -10dB and -20dB level reduction switch for hot signals and a link output for connecting a separate amp or monitor.  The value for money is very good as well.  I have used cheaper brands but the quality just isn’t as good.

– Reviewed By: Matt Rowbottom, c/o Absolute Music, Poole