If you have been associated with live or studio production and recording for any length of time, you have most likely heard the words “direct box”, “direct input box” or simply “DI”. It’s usually a small black box that an instrument cable is connected to that sends the mixing board what it needs to get the instrument in the mix.
Over the years, questions have come my way concerning the use and purchase of a direct box. This is not a know-all, end-all article on the use of a “DI,” but it is information I have gleaned in live and studio production.
What is a direct box?
Here we go! Most instruments send out unbalanced signals on only two wires that aren’t as strong as mic level signals. An electric guitar cable that is mono unbalance is limited to carry the signal around 15 feet or so. Beyond that, it is subject to signal loss, tone loss, and possibly interference. Therefore, something is needed to convert unbalanced cables to balanced ones. Hence, the direct box to the rescue.
Not only does the “DI” help with balance but also impedance. If you have seen the term Lo-Z, this is where this comes in. A mic sends a low impedance, low voltage, high current signal that’s called a Lo-Z. An electric guitar is sending a signal that is Hi-Z, high impedance, high voltage, and low current. The direct box converts the guitar’s Hi-Z to a Lo-Z so it can be sent a much greater distance through a cable to the mixing board.
That’s the essence of a direct box without all the background geek speak associated with it. There are different versions of direct boxes – passive, active and somewhat specialized versions. In this article, we are dealing with the most commonly used, which is the passive unit. It’s designed to do one thing: Convert Hi-Z (input) to Lo-Z (output). Some passive direct boxes can have a ground loop switch that will help with ground hum. That’s all they do. No power supply is needed because of how the transformers work inside. Well then, you may ask does whether price matters when it comes to direct boxes.
What about prices for a direct box?
The consensus is that there can be more coloring of the audio by low-priced units. However, in comparing mid-priced to high-priced showed little difference and all price levels can be influenced by other equipment in the audio chain. You should consider how long the direct box will be in service. A $60 to $70 unit used over 5 years is a good deal compared to a $30 unit. That being said, I have had very good success with $40 range direct boxes thru the years. Plus, being thrown around, misused and coming up missing, that price
point could be a better deal.