BOSS's perennial favourite tuner, the TU-3, is the latest incarnation of a unit that has been the fundamental centre of thousands of rigs over the last few decades.
Apart form accuracy (this one is within one cent), there isn't much you need a tuner to have but there are a few important features. Visibility is one and the TU-3 gives you a strong visual reference with a 21 segment LED that can be super-bright (you can dial that back if it's too much!) and easy to work with on a dark stage.
Other useful features include modes for Guitar and Bass, (including 7 string guitars and 6 string basses), modes for drop tunings by the semi-tone, an automatic signal mute when the pedal is engaged and, rather excellently, it behaves like a power supply for other pedals if used with a PSA power supply and daisy chain. Much more, then, than just a great tuner.
Choose between Chromatic or Guitar/Bass tuning modes, and enjoy visual pinpoint tuning verification with the Accu-Pitch Sign function. The TU-3 incorporates a convenient Note Name Indicator that can display notes of 7-string guitars and 6-string basses, while the Flat-Tuning mode can support up to six half-steps. It’s the new-standard tuner that no guitarist or bass player should be without!
21-segment LED meter with brightness control
High-Brightness mode enhances meter visibility outdoors
Accu-Pitch Sign function provides visual verification when tuning is complete
Chromatic and Guitar/Bass mode (tune by string number, with support for 7-string guitars and 6-string basses)
Flat tuning is supported with Guitar Flat mode, which allows for “drop” tunings up to six semitones below standard pitch
Tuner automatically mutes when the tuner is on
Supplies power for up to 7 BOSS compact effect pedals