A quick guide to guitar tuners
The most obvious thing to strike you when you start looking for a guitar tuner is that there are just so many to choose from, and covering a huge price range. For a novice, or even someone who hasn't bought a tuner for a long time, this can be quite daunting. So let's give an quick overview to help you.
The most important point is that you want a tuner that will allow you to tune your instrument quickly, precisely and at a price that suits your budget. To achieve this, we need to address several issues.
If you don't know what a cent is, you have most likely heard it mentioned, or seen it mentioned in specifications. Simply, a cent is one hundredth of a semitone (i.e., 1%). A semitone corresponds to one fret on a guitar fingerboard. It is more convenient to talk in cents when talking about fine tuning, rather than semitones: 2 cents sharp is much easier than saying 0.02 semitones sharp!
Often people will tell you that "a few cents" is close enough. For some uses, this is true, but when playing chords the difference between 1 or 2 cents and 0.1 or 0.2 cents is quite audible. It doesn't necessarily sound more "in tune", but it does sound warmer, sweeter and your instrument starts to sing. We believe that it is important that tuning should always be done to less than 1 cent, preferably less than half a cent. We call this "sub-cent tuning".
"We believe that it is important that tuning should always be done to less than 1 cent, preferably less than half a cent. We call this sub-cent tuning"
Reference frequency (A440)
The reference frequency is the frequency around which all other notes are based. Conventionally, this is an A at a frequency of exactly 440Hz. However, it is not uncommon for small deviations to this to be used, such as 442Hz or 444Hz. Many tuners will allow you to change this over a small range. If in doubt, it is best to leave this on the default 440Hz setting.
Note that it you want to be in tune with something that can't be easily tuned such as a piano, you need to be able to adjust the reference frequency of your tuner to match the other instrument. To make this easier, many tuners include a "learn" mode where it will adjust the reference pitch to match what you play into it.
Accuracy is a word that is often misused in tuner brochures and specifications. To achieve sub-cent tuning, three factors need to work in harmony: accuracy, resolution and the display indicator.
Correctly, accuracy is how close the built-in tuner reference frequency is to its nominal value. Is the 440Hz reference frequency actually 440.01Hz or 439.99Hz? This matters because if this isn't correct, you will still be able to tune your own instrument accurately but you will not be perfectly in tune with another instrument tuned with another tuner.
Resolution is how fine the measurable steps are. For example, if a tuner is perfectly accurate but can only measure in 2 cent steps, when you are somewhere between +2 and -2 cents you will have no idea where you are— the "in tune" indication may be shown, but you could still be 1 or more cents out of tune. This highlights the importance of resolution working together with accuracy. Accuracy must be close enough to the true reference frequency, and the resolution must be fine enough to measure precisely.
For you to tune accurately, it is essential that you can actually see the fine resolution of the tuner so that you can act on it (i.e., stop tuning when "in tune").Many cheap tuners use LCD segment displays to simulate moving needles, or other flat/sharp indicators. The biggest problem with this is that the inherent resolution of the display is very low — there are only a limited number of "needle positions" that can be shown, so even if the tuner is very accurate, and internally very precise, this can't be shown to you!
A good tuner needs a good way to display when something is in tune
All sonuus tuners have highly accurate internal clocks, include our proprietary high-resolution frequency measurement algorithms, and use various ways to display the tuning information so that none of this accuracy and precision is lost. This ensures you can tune accurately, precisely and quickly.