Linear outputs
The number of line outputs provided in the design of the digital piano.
The line output allows you to send the sound from the instrument to external audio equipment. In this case, the sound is transmitted in an analogue format, and to play it, it is enough to pass it through a power amplifier; and active acoustics can generally be connected directly to the line output. The outputs themselves can use different types of connectors, but most often they are 3.5 mm mini-Jack or 6.35 mm Jack, compatible with most audio equipment either directly or through the simplest adapters.
Multiple line outputs allow you to connect multiple signal receivers to the instrument at once — for example, speakers with an amplifier for playback and an external recorder for recording. However, digital pianos rarely have more than 2 line outputs — more, taking into account the specifics of the use of such instruments, is simply not required.
Number of bands
The number of bands provided in the Digital Piano's native acoustics.
In single-way acoustics, the speakers are responsible for reproducing the entire frequency range. Such systems are simple and inexpensive, but their amplitude-frequency response is far from perfect — most often they reproduce the mids well, but the bass turns out to be weak and unsaturated, the high frequencies are fuzzy and blurry. This is due to the fact that for each frequency there are separate requirements for the design of the speaker, and it is impossible to combine them in one speaker.
Thus, loudspeakers, including the built-in speakers of digital pianos, can be split into bands when the design provides for specialized speakers for a certain group of frequencies. The most advanced variant found in digital pianos is three-way, with separate sets of drivers for bass, mids, and treble. This allows you to achieve high-quality and reliable sound throughout the entire range, but complicates and increases the cost of the design. Therefore, three-way acoustics are rare, mainly in top-class instruments. But in mid-range instruments, two-way speakers are more often used (high frequencies on one set of speakers, medium plus low frequencies on the other).
