Can I connect DI box to mixer line in?

Question

I am presently feeding my DI boxes through a multicore and into my mixers XLR mic inputs. However I wonder if I could feed them into the line inputs (1/4" jack) instead.

I would obviously need to make up some XLR to jack converters, but if possible it would free up some mic inputs as I am running out of channels!

1. Can I feed DI box output into the line inputs in my mixer?

2. If so, will phantom power from the mixer to the DIs work?

3. And can I connect the DI boxes to line input channels with double numbers (i.e. 9/10, 11/12 - what do they mean)?

I should explain the background to my question. For years, when mixing live sound, I have had a surplus of channels and have arranged them to mimic what I see on the stage. So you see I had no use for the 'line in' channels other than as an input for pre-recorded music. However I recently ran out of channels and thought it should be possible to run a Roland pro keyboard (currently thru' an active Thomann DI-33/10meter lead/30meter multicore) in stereo to the currently spare stereo 'line in' channel on the desk. This has now proved to be OK, so for the cost of some XLR/TRS leads, a couple of 9v batteries, and the slight inconvenience of the keyboard being in the 'wrong' place ! I have gained an extra pair of mic channels, with the potential for even more. My thanks for your help in answering a very basic question

Answer 1

1. "Can I feed DI box output into the line inputs in my mixer?"

Your typical Behringer mixer has a gain range of -10 to +40 dB with the line in, but this varies from mixer to mixer (look it up in the specs section of the manual). The signal level from the DI box greatly depends on what you connect to it and the DI box model. But generally you get ranges from -10 to -30 dB.

In general if the DI box has one or more PAD switches that let you attenuate the signal e.g. -20 db, make sure you do not enable these. This also applies to the use of PAD switches on the mixer channel input.

You will have no problems getting optimal gain with things like laptops, keyboards and other preamplified sources (active basses and westerns).

Passive signals from basses and guitars etc may pose a problem gain wise, but it will work, perhaps just not as loud as you'd want and you may have to compensate by lowering gain/volume on other channels.

Impedance-wise there should be no problem connecting a DI (low impedance, typically < 300 Ohm) to the line input (high impedance, typically > 10KOhm).

What you need to check up on is if the Line In is balanced (preferred for low noise) and use a balanced cable between DI and mixer. If the input is balaced, you should use a three pole TRS ("stereo jack") connector into the mixer.

2. "If so, will phantom power from the mixer to the DI's work?"

No. Line inputs should never be phantom power enabled. If they are it is a really bad mixer design. I have never seen this design used. You have to go with Passive DI boxes or power them by battery.

3. "Can I connect the DI boxes to line input channels with double numbers (i.e. 9/10, 11/12)"

These are typically reserved to stereo inputs. The channel controls are ganged to work with both channels at once. You can use these, just be aware of the restrictions. One of the channels (typically the first) of a pair is mono enabled, so you can use that alone and forget about the other one (and still have a panning enabled input). Again make sure you notice the balanced/unbalanced status of the input.

Answer 2

Some very good answers already given, let me add some easy to follow practices, as you really did not specify what your specifics are (e.g. what device/guitar/instrument you are using):

Active DI or Passive DI?

Active DI usually have a battery or powersupply, and contain a more complex circuitry inside; a Passive DI could be as simple as a transformer inside.

• use an Active DI for a passive device.
• use a Passive DI for an active device.

Hi-Z to Low-Z or Low-Z to Hi-Z?

Various DI boxes exists, with either Low-Z or Hi-Z inputs and or outputs. Use an appropriate DI to change the Z (impedance) to match your input of your mixer. Some DI's the circuit is reversable, and work both ways, but ensure you check the DI documentation before you plug anything into it.

• Hi-Z device to Lo-Z input of mixer: use Hi-Z to Low-Z DI
• Low-Z device to Hi-Z input of mixer: use Low-Z to Hi-Z DI

Balanced or Unbalanced?

DI boxes are used to change the unbalanced signals to balanced signals. If you are running long leads/snake to your mixer, it might be beneficial to change unbalanced signals to balanced. This due the reduced noise/inteference pickup of balanced signals.

To "pad" or not?

Make sure you know what levels your signals are, and what your mixer expects, this to avoid clipping. Best is to know the gear your are working with and read the documentation. Use padding to lower the signal if needed before the mixer. I

There are DI boxes who do all of the above, and there are DI boxes which only do one or two of the above. You need to figure out what features you need, and what type of DI will suite your setup.

The above are just "rule of thumb" and there are many situation thinkable where you need to divert from those.

HTH.