LAG668F Audio Chip

The LAG 668 F is a monolithic integrated circuit (IC) for stereo cassette players, manufactured by the Mitsumi Corporation. It is extremely useful for portable headphone devices and provides a very cost effective bass boost function. The addition of three resistors and one capacitor (per channel) is enough to enable the bass boost function. The chip has preamplifiers, and power amplifiers to drive a pair of headphones. The power output is 30 mW in a 16 Ω load. It also provides motor control and speed regulation as well as noise suppression.

This is an interesting and unusual circuit, and the sound is unique as well.

Circuit Diagram

The coils from the audio heads connect directly to pin 2 and pin 27 of the preamplifier inputs.

Pin 4, pin 5, and pin 6 are where the additional components connect for the bass boost function. The documentation of this IC comes with standard equations to calculate the component values of the boost frequency required.

This IC requires very few external components, and the output from pin 9 and pin 19 connect directly to the stereo jack socket without any decoupling capacitors.

This Article Continues...