Features 1、The tuning board has the stability, powerful functions and reliability of a micro controller. You can be sure that the audio board works properly when connected to most audio sources. 2、This tuning version is a passive tuning board, the tuning board does not need power supply, which solves the problem of wanting to use it even when there is no electricity. 3、The main function of the tuning board is to adjust the high and low sounds of the input audio signal, and then send it to the power amplifier board for amplification. 4、The principle of the tuning board is to filter the audio signal directly through the resistance capacitance component to obtain the desired high and low sounds. 5、The tuning board is easy to install, and the installation of the sound board is simple, without particularly complicated operations. Specification Item Type: Tone Board Adjustable Items: Total Volume, Treble and Bass Number of Channels: Two Channels Knob Spacing: Approx. 22.5mm / 0.9in Socket Type: XH2.54-3P Appearance Size: Approx. 56 x 28mm / 2.2 x 1.1in Package List 1 x Passive Tuning Board 3 x Nut 3 x Gasket