Stereo power amplifier with integrated circuits TDA7233. The load of the amplifier can be headphones with impedance greater than 2Ω. The best results are achieved with headphones with an impedance of 32Ω.
• AB class power amplifier.
• Output power: 800mW at RL=32Ω and Vcc=12V DC.
• THD is less than 0.3%.
• Bandwidth: 17Hz-23kHz.
• Supply voltage: 3-15V DC.
• Power consumption in the standby mode approx 6mA / channel.
• PCB dimension: 48×60mm.
• Electronic Kit – soldering required.
Schematic diagram of the amplifier is shown in Figure 1. Both channels are identical and each contains integrated circuit TDA7233. The C9 and C10 capacitors form a loop of negative feedback for alternating current. The inclusion of 5,1Ω resistors in series with these capacitors causes a decrease in the voltage gain of the power stage, which reduces the nonlinear distortion and harmonic frequency level in the output signal. The audio output signal is fed through capacitors C4 and C8 to the output connector to which the headphones are connected directly. They can be any magnetodynamic headphones with an impedance greater than 2Ω.
Assembly and test
The assembly is typical and should not cause the problems. It runs in standard way starting from the smallest components and ending with the largest ones. During assembly the polarity of the components (electrolytic capacitors, transistors, diodes) should be noted.
After completing the assembly, the polarization of the components on the PCB and the short circuiting of the soldering points should be carefully checked. Correct assembly ensures immediate and trouble-free commissioning of the amplifier.
R1, R3: 10kΩ
R2, R4: 5,1Ω
R5, R6: 1,2Ω
PR1: Rotary potentiometer 2×50kΩ
C1, C5: 220nF
C2, C4, C6: 100µF
C3, C7: 22µF
C8, C11, C14: 100µF
C9, C10, C12: 100nF
C13, C16: 10µF
C15, C17, C18: 100nF
LD1: LED diode
US1, US2: TDA7233
X2, X3: 3.5mm Stereo Audio Jack
X1: 2-pin terminal block connector