What is a DI Box?  What does it do?  Why is it used or preferred or even necessary with a keyboard?

I am also trying to put together a small PA system that is accurate at low volume levels when I’m mixing tracks at home but reproduces and translates live onstage at higher volumes.  (I also sing and run everything through a little Yamaha Mixer.)

I’ve heard very good reviews of the Yamaha DXR 10” speakers. Also, QSC K10”.

So, speakers, recommendations?  DI Box? If I need one, which model?

1) A DI box converts a high-impedance, line-level, unbalanced signal (which your keyboard sends via the main outs) to a low-impedance, balanced signal (like that of a microphone).  Balanced signals are much less prone to the introduction of noise, especially over a significant distance.

If you do not have any buzz or RF issues, and are running short cables between your keyboards and mixer, and/or don’t need to go to FOH with your sub-mix, you probably do not need a DI box. 

They are commonly used with keyboards to convert the signal, prior to sending it through a snake to the FOH equipment, as the long distances can create bad hiss problems using unbalanced signal cables.  Under about 15’ of cable length, an unbalanced signal usually doesn’t introduce significant noise into the signal path.

I do use a DI box with my live rig, and can highly recommend one of These, if you decide to get one.

2) I’ve used a pair of DXR10s as stereo monitors in my live keyboard rig for several years, and really love them.

Thanks. Helpful information.

In general, line level signals (like the output of a synth) do not need DI boxes. Period. Full stop. The 15 foot limit mentioned is for passive high impedance signals like guitars and hi-Z mikes. Low impedance mikes can easily be run over 100 feet of cable without any problems.

However DI boxes can still be useful in cases where the synth output is 1/4” and the mixer inputs are XLR only, a splitter is required to drive both the PA and a stage amp or where ground loops are a problem.

To the OP, I would highly recommend you study This Document, referenced and linked by 5pinDIN in This Thread.

I have not obtained satisfactory results running long unbalanced cables from my Yamaha keyboards, and found the answer in a quality DI box within a short distance of the signal source. I no longer run unbalanced signals beyond approximately 15’, based on my experience.  Others may have a different experience. 

These links will provide valuable guidance in setting up your live rig for great results.