2x30W Stereo Amplifier with TDA1521

Technical data:

2x12V power supply

Maximum RMS power 2x15W / 4ohm or 2x10W / 8ohm

Maximum musical power 2x30W / 4ohm

Sensitivity 300mV / 20Kohm

7Hz ... 60kHz (-3dB) frequency band

98db signal-to-noise ratio

Crosstalk -70db

Overload and short circuit protection

The stereo audio amplifier, although compact, delivers a high quality signal and relatively high power output thanks to the integrated TDA1521. The total amplification is, for each channel, 30dB. The TDA1521 integrated circuit requires a suitable radiator. The inputs of the two internal amplifiers are found on pins -INV1 and INV2, in series with non-polarized 1uF capacitors. Because the supply is made with two symmetrical voltages of + -12V, the speakers connect galvanically between the two outputs and the center of ground point. In order to avoid possible parasitic oscillations of high frequencies, two attenuation networks formed by RC groups were connected to the two outputs. These have the role of reducing the phase shift between the input and output signals, given that the loads have a predominantly inductive character (speakers.)

Inputs INV1 and INV2 are connected to ground.

The power supply of the amplifier is made in alternating current. For this we need a transformer that provides a secondary 2x12V signal. The rectification of the alternating voltage is done with 4 diodes of type 1N5404, and the filtration with the two capacitors of 4700uF each, connected in series. The role of the 100nF capacitor is to filter out any high frequency signals.