Contributed by David Jiang for the Roland Australia Blog
Have you ever found your perfect tone, then plugged your instrument into a PA or recording desk and found that you didn’t have the correct connectors and that it was creating a strange humming sound that you just couldn’t get rid of?
Chances are that either you are using an unbalanced (sometimes referred to as mono) cable that is too long and is picking up noise or that your gear is suffering from a ground loop. Sometimes this can be fixed by shortening your cable length or plugging both units in to the same power socket with a power strip. However, this does not always do the trick. That is why a BOSS DI-1
Direct Injection box is a must have piece in any musicians kit.
So what does a BOSS DI-1 do?
At its most basic level, it changes your jack input to an XLR. Why not just use a cable with a jack on one end and an XLR on the other though? The answer is all about signal quality. To ensure that you aren’t losing any of your signal and to wipe out any possible noise issues, you need a DI box.
To ensure you have the clearest signal possible you need to make sure that your instruments impedance matches what you are plugging in to. Without getting into specifics, a high output impedance instrument like a guitar or bass will lose high end frequencies when plugged in to a low impedance input such as those on professional mixers or recording interfaces. The DI-1 takes the high impedance signal from your guitar and turns it into a low impedance signal so that your signal comes through as you intend it.
With regard to noise. The first problem arises when an unbalanced cable is run for a long distance, The longer the cable is, the higher the possibility of it picking up noise from outside sources. A DI-1 takes the signal from an unbalanced instrument such as a guitar, bass, electronic drum kit, synth or keyboard and turn the signal into a balanced output. A balanced audio cable carries two copies of the instrument’s signal through two separate wires. One of these copies is flipped 180° or polarity reversed so that when the cable gets to the mixing desk any noise picked up by the cable can be isolated by combining the two signals together.
How does it do this? Well, think of your audio signal as a person pulling and pushing on a motor boat’s tiller. On it’s own, the tiller will move and steer the ship in the direction that the person is moving it, only affected slightly by current in the water (this is the noise). Now imagine there are two tillers connected to the motor and second person pushing and pulling at the exact opposite force. They two tillers would cancel each other out and The only steering changes would be caused by the current.
The resulting noise is then once again flipped by 180° and combined it with the original signal to leave it clean and clear. This solves the problem of cable length noise.
However, this still leaves the problem of ground loops. A ground loop is caused when two electrical devices are plugged in and the electric potential in the ground wire of each device is different. This mismatch causes some of the electrical energy to be transferred through the audio wire between the units to try and achieve balance.
An old trick was to physically remove the ground pin from the units but this was very dangerous as bad wiring and electrical surges could electrify the case of the instrument and cause fires or even electrocution (Do not try it on your own gear). The BOSS DI-1 has a ground lift switch which safely cuts the connection between the ground wires of each instrument removing the extra noise from your signal.
So what else can a BOSS DI-1 do?
As well as performing the functions of your regular DI box, there are some great features that really make the DI-1 stand out.
Unbalanced and parallel outputs allow you to send your signal to an on stage monitor or guitar amp as well as the mixing desk.
Battery power allows you to run the DI-1 even if you don’t have phantom power on your mixing desk.
Inbuilt -20dB and -40dB pad switch allows you to tame very hot signal levels at the source so you don’t distort your signal in the mixer.
Polarity invert switch for fixing phase cancellation issues.
All in all, the BOSS DI-1 is a must have tool to make sure your music sounds great both in the studio and on stage.