Sanyo M4440 Audio Chips

Here you can see the three audio chips in a SIL package. The vertically oriented chip is the stereo preamplifier. The two horizontally oriented chips are the headphone power amplifiers, capable of delivering a maximum of half watt to each channel. However, in practice it will be much less, as there are limiting resistors in this circuit to prevent full power output for safety reasons.

The two transistors and green pairs of capacitors form the stereo filter circuit to boost the tone level. They have used discrete components for this function and it seems to work very well.

The motor receives its voltage via a three transistor regulator circuit, and it does a good job of maintaining constant speed as the battery power drops.

There are many electrolytic capacitors in the power section to keep the voltage smooth and noise free. Consequently, this cassette player has a very sharp sound that is loud, clear, and very reminiscent of the 80s.

Preamplifier IC

The signal from the audio head goes directly into this preamplifier chip. Pressing the talk button diverts the signal from the built-in microphone to this preamplifier IC.

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