BTL amplifier using HA1392

HA1392 is a high-fidelity power amplifier integrated circuit. Many foreign famous brand cassette recorders (such as Sharp GF555, GF666, GF777, etc.) use it as audio power amplifier. The quiescent current of HA1392 is very small (36mA), and crossover distortion occurs
under low current.
Extremely small. It has an audio squelch circuit inside, which can achieve a 60dB squelch suppression ratio under the SmA squelch control current.
Since its heat sink is connected to the "ground" point of the internal circuit, it can be directly installed on the bottom case of the whole machine. No additional insulation is required
. There are two independent power amplifiers and squelch control circuits inside HA1392.
    Figure 2-48 is a two-channel power amplifier with tone control composed of two HA1392 and one BA328.
Each channel of the power amplifier uses a W1392, and the two internal independent power amplifiers are connected in BTL form.
Each channel can obtain 22W of audio power at a certain load. Among them, pin 2 is the signal input terminal, pins 7, 1 and 2 are the output terminals,
which can be directly connected to the speaker ocla. C19 is a bootstrap capacitor, C16 and C17 are inverting DC decoupling capacitors, c15 is a ripple suppression
capacitor, ‰, C21 is the phase compensation capacitor. Riz is the input resistor o R13 is the gain control resistor. The left and right symmetric components
are the same.
    VTt and related components form an attenuated tone control circuit, which has a control capability of ±20dB for both treble and bass. The
pre
    -balanced amplifier of this machine is a BA328, which is characterized by a wide power supply voltage range and a built-in
bias circuit. , less foreign components , high open-loop gain, low noise, excellent dual-channel balance characteristics, and wide dynamic range.
oC1 is the input coupling capacitor, c4 is the output coupling capacitor, and C3 is the AC bypass capacitor. C22 and & form a power supply filter
, C5-R3, and R2 together form a frequency equalization network. Ri is the feedback resistor. Changing the resistance value of Ri can change the gain
.
    The input sensitivity of BA328 is very high. CKi can directly input the signal of the recording and playback head or the microphone signal. The output
voltage can reach a maximum of 1.5vo. The reduced noise voltage of the input terminal of BA328 is about 1-2uV. The crosstalk level is -65dB, and the harmonic distortion is
is 0,1% (input 300mV). CK2 can input the line output signal (260rnV) of other audio equipment or
the output signal of the record player crystal cartridge. If self-excitation occurs during debugging of
    the machine , you should first find out whether it comes from the preamplifier stage or the power amplifier stage. If it is a pre-stage, you can adjust the resistance of Ri to reduce the gain of BA328. If the power amplifier is self-excited, you can increase the value of R13 or cl6, or you can connect an o.1 between pins 9 and 10 of HA1392. ~0.33L1 capacitance. Self-excitation can be eliminated. During debugging , do not allow the output pins 7 and 12 of the HA1392 to touch the "ground" or the positive power supply to prevent the power amplifier integrated circuit from burning out.