In this post, I will present a power amplifier circuit with integrated circuit TDA2030 2.1 or LM1875 2.1 or TDA2050 2.1, which can provide up to 72W RMS of power, with 18W for each stereo channel and 36W for the subwoofer channel. This circuit is ideal for those who want to assemble a 2.1 sound system for their computer, TV, or other audio device.

The TDA2030 integrated circuit is a class AB audio amplifier that can operate with voltages up to 36V and currents up to 3.5A. It has good sound quality, low distortion, and thermal and short-circuit protection. It can be used in both simple and bridge configurations to increase output power.

The LM1875 is an integrated circuit that allows the construction of high-quality, low-distortion audio amplifiers. The LM1875 can provide up to 20 watts of power with 4 or 8 ohm loads, using a symmetrical power supply.

The TDA2050 is a monolithic-integrated circuit in a Pentawatt package, designed for use as a class AB audio amplifier. Due to its high-power capacity, the TDA2050 is capable of delivering up to 35 W of true RMS power into a 4 ohm load at THD = 0%, VS = ±18 V, f = 1 kHz, and up to 32 W into an 8 ohm load at THD = 10%, VS = ±22 V, f = 1 kHz.

The schematic diagram of the TDA2030 2.1 amplifier.

Regarding the circuit, the one I will present uses two TDA2030s for the stereo channels (left and right) and a bridge TDA2030 for the subwoofer channel (bass). Additionally, it utilizes a dual operational amplifier NE5532 to elaborate the preamplifier and low-pass filter for the subwoofer channel. The NE5532 is a low-noise and high-speed operational amplifier widely used in audio applications.

See also:

• TDA2030 2.1 amplifier board subwoofer circuit diagram
• Circuit Preamplifier 2.1 stereo tone control + subwoofer
• TDA2030 2.1 amplifier board circuit diagram subwoofer
• TDA7294 2.1 TDA7293 2.1 power amplifier circuit
• TDA7377 2.1 amplifier circuit diagram with PCB
• TDA7377 2.1 amplifier circuit diagram with PCB

The circuit is powered by a symmetrical 12V + 12V source, which can be obtained from a transformer with dual 12V secondary and a rectifier bridge with filtering capacitors. The source also employs two voltage regulators, LM7812 and LM7912, to provide a stable 12V voltage to the operational amplifier. Furthermore, 10nF capacitors are used in the source to reduce high-frequency noise and filter out potential noise caused by diode switching. Large capacitors of 6,800uF or 10,000uF are also utilized for source filtering.

At the input, we have a 1M resistor to mitigate noise when the input is without signal. The capacitor C16 with R11 forms a high-pass filter with a cut-off frequency of 1.5Hz. The resistor R13 and capacitor C19 form a low-pass filter with a cut-off frequency of 723 KHz. If desired, you may alter the values of these components according to your needs.

The potentiometer P1 adjusts the volume of the stereo channel, while the potentiometer P3 adjusts the volume of the bass channel. The components around P3 form a tone control.

The operational amplifier is configured for a gain of 2, but you may alter this if desired. Adding capacitor C22, we have a low-pass filter and attempt to keep RF signals out of our circuit.

In the pre-amplifier of the bass filter for the subwoofer channel, we have an active low-pass filter around IC4B with a cut-off frequency of 159 Hz. IC4A will raise the audio signal level by 5.7X before being applied to the power amplifier of the subwoofer channel. This may be altered according to your needs.

Recommendation of a printed circuit board to assemble the amplifier.

After assembling the circuit, you can test it by connecting an audio source to the input and the speakers to the output. You can adjust the volume of the stereo channels and the subwoofer using the corresponding potentiometers. Additionally, you may modify the cutoff frequency of the low-pass filter for the subwoofer by altering the values of the components surrounding IC4B.

BOM for assembling TDA2030 2.1 or LM1875 2.1.

Latest update: 03/03/2023 19:00.