Enthusiast Reverse Engineering Sound Amplifier for Popular Handheld Console

This is a sound amplifier, which was put in the game console Nintendo Game Boy Color.

Earlier we talked about Sound Blaster 1.0 and the card for the IBM PC – Innovation SSI-2001.

Photo Elias castillo / Unsplash

Nintendo’s Portable Game Boy Color System released in 1998. Hundreds of games in various genres were released on it: from arcades and strategies to survival horror. The latter category includes Alone in the Dark: The New Nightmare and Resident Evil Gaiden.

Deeper into the atmosphere of games allowed the acoustic components of the console. The device had both a built-in mono speaker and a port for connecting stereo headphones.

A microchip consisting of three amplifiers was responsible for processing the sound. It is his reverse engineering spent Ken Shirriff, a software developer and a fan of vintage computing.

How is the chip arranged?

For reverse engineering, Ken Shiriff used crystal pictures. He found that in the upper left of the chip are two large resistors for outputs to the speaker.

These are the so-called pull-up resistorsguaranteeing high and low voltage levels respectively. The components themselves are strips of p-type semiconductor (silicon) in zigzag shapeto save space on the board.

Photo John mcmaster / CC BY

As for the headphone amplifiers, they consist of identical sides. They include differential pairs, current mirrors and other service integrated circuits.

In this case, the amplifier circuits for headphones, in contrast to the amplifier for the speaker, contains not two, but ten pull-up resistors. Five pieces per voltage level. They also serve to form negative feedback.

The control logic is located in the lower left part of the chip. It switches the operating modes of the device (headphones / speaker) – depending on the occupancy of the 3.5 mm port.

Complete Ken Chiriff chip diagram posted on github.

Related projects

At the end of last year, another enthusiast conducted reverse engineering of the entire on-chip (SoC) system for GameBoy. He placed the drawn diagrams in repository on GitHub – the logic of work entered there APU, PPUas well as input / output systems. According to the author, the “inner world” of the console is full of unusual solutions. He spent 191 hours searching for all the compounds and drawing up the drawings.

Photo Hello I’m Nik / Unsplash

You can also find the Game Boy emulator on GitHub – Mooneye GB – written in Rust. The list of supported devices includes many versions of the console: from the original console to Game Boy Color and Game Boy Advance SP. Moreover, the project has a detailed technical documentationwhich is regularly updated (the latest revision was April 18).

Additional reading in the “Hi-Fi World”:

“Rhythm games worth knowing”: which projects put on sound and made it part of the genre
Video Game Music Makers: Some Distinguished Names
Where to get audio for game development? Libraries with the sounds of nature
What are the features and tasks of the soundtrack of games

What to read at us on Habré:

  • What neural networks can “sing” and perform death metal
  • Voice assistants at the wheel – why they are not always needed and not for everyone
  • The history of audio formats – the era of cassettes and the development of speech synthesis technologies

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