A double bass tuner is similar to most other types of electronic tuners. It "listens" to the note you play on your bass and gives you feedback on its tuning. In order to find the best double bass tuner for you, determine your priorities, whether that is a hands free design, accuracy, or some other feature. You can find a double bass tuner, or similar electronic tuner, in music shops and online retailers.
There are basically two types of tuners: sweep and strobe. A sweep double bass tuner has a physical or digital gauge that represents the tuning of the note played. The center of the gauge is ideal for the note, and if the gauge falls to the left, the note is flat. If it falls to the right, the note is sharp. To tune the bass, the tension is adjusted on the string until the gauge centers.
A strobe tuner uses an ideal pitch rather than an average of sound waves. The strobe looks like a spinning dial, and the faster it spins, the more out of tune the note. As the note is brought into tune, the strobe slows. When the note reaches ideal pitch, the strobe stops spinning altogether.
Sweep tuners are the most common and the least expensive. Even so, they lack the accuracy of the strobe. They actually take the sound waves from the note played and compare them. The average wavelength is used as the ideal note. This can be a problem in noisy areas. A strobe tuner may be more expensive, but it is more accurate, especially in noisy settings. Extreme accuracy, however, is not usually necessary.
Your budget will determine whether you can afford the high cost of a strobe double bass tuner. For some studio musicians, who play against electronic and computerized instruments, there is no room for any tuning inaccuracies. Other musicians, who play live gigs or who play simply for their own enjoyment, will probably find a high quality sweep tuner to be a better choice.
Both sweep and strobe double bass tuners come in clip-on and block styles. The advantage of a clip-on tuner is that it attaches to your instrument, leaving your hands free while tuning. It also keeps the tuner in an area where it is easily visible. The disadvantage is that most clip-on tuners do not have a jack. If you rely on a pick up on your double bass, or if you use an electric double bass, an input is usually a necessity for fast and accurate tuning.