Electronic Tuner - Strobe Tuner - How A Strobe Tuner Works

How A Strobe Tuner Works

Mechanical strobe tuners have a series of lamps or LEDs powered by amplified audio from the instrument; they flash (or strobe) at the same frequency as the input signal. For instance an 'A' played on a guitar's 6th string at the 5th fret has the frequency of 110 Hz when in tune. An 'A' played on the 1st string at the 5th fret vibrates at 440 Hz. As such, the lamps would flash either 110 or 440 times per second in the above examples. In front of these flashing lights is a motor-driven, translucent printed disc with rings of alternating transparent and opaque sectors.

This disc rotates at a fixed specific speed, set by the user. Each disc rotation speed is set to a particular frequency of the desired note. If the note being played (and making the lamps behind the disc flash) is at exactly the same frequency as the spinning of the disc, then the disc appears to be static (due to an optical illusion) from the strobing effect. If the note is out of tune then the pattern appears to be moving as the light flashing and the disc rotation are out of sync from each other. The more out of tune the played note is, the faster the pattern seems to be moving, although in reality it always spins at the same speed for a given note.

Many good turntables for vinyl disc records have stroboscopic patterns lit by the incoming AC power (mains). The power frequency, either 50 or 60 Hz, serves as the reference, although commercial power frequency is sometimes shifted slightly to meet load demand. The operating principle is the same; although turntable speed is adjusted to stop drifting of the pattern.

As the disc has multiple bands, each with different spacings, each band can be read for different partials within one note. As such, extremely fine tuning can be obtained, because the user can tune to a particular partial within a given note. This is impossible on regular needle, LCD or LED tuners. The strobe system is about 30 times more accurate than a quality electronic tuner, being accurate to 1/10 of a cent. Advertisements for the Sonic Research LED strobe claim that it is accurate to 0.0017 of one semitone or 1/6 of a cent.

Strobe units can often be calibrated for many tunings and preset temperaments and allow for custom temperament programming, stretched tuning, "sweetened" temperament tunings and Buzz Feiten tuning modifications. Due to their accuracy and ability to display partials even on instruments with a very short 'voice', strobe tuners can perform tuning tasks that would be very difficult, if not impossible, for needle-type tuners. For instance, needle/LED display type tuners cannot track the signal to identify a tone of the Caribbean steelpan (often nicknamed the "steeldrum") due to its very short 'voice'. A tuner needs to able to detect the first few partials for tuning such an instrument, which means that only a strobe tuner can be used for steelpan tuning. This is also true of musical pins used in music producing machines like Music Boxes and the like. In such cases a technician has to physically trim off metal from the pin to reach the desired note. The metal pin will only resonate a little when struck. Great accuracy is required as once the metal is trimmed or filed a permanent change in the pin takes place. As such, the strobe-type tuners are the unit of choice for such tasks. Tuners with an accuracy of better than 0.2 cent are required for guitar intonation tuning.

One of the most expensive strobe tuners is the Peterson "Strobe Center", which has twelve separate mechanical strobe displays; one for each note in the chromatic scale. This unit (retailing at about $3,500 US) can tune multiple notes of a sound or chord, displaying each note's overtone sub-structure simultaneously. This gives an overall picture of tuning within a sound, note or chord, which is not possible with any other tuning device. It is often used for tuning complex instruments/sound sources or difficult-to-tune instruments where the technician requires a very accurate and complete aural picture of an instrument's output. For instance, when tuning musical bells, this model will display several of the bell's partials (hum, second partial, tierce, quint and nominal/naming note) as well as the prime, and each of their partials, on separate displays. The unit is heavy and fragile, and it requires a regular maintenance schedule. Each of the twelve displays requires re-calibration over time, dependent on how much it is used. It can be used to teach students about note substructures, which show on the separate strobing displays.