- Pulse Channel
- Triangle Channel
- Noise Channel
Nintendo Entertainment System is the 8bit console we all love. Its square, gray shell taught use the joys of plastic. The NES was released in 1985 in North America, Europe, Australia and Brazil after the popularity of Nintendos Famicom
in Japan. Nintendo claims it sold 61.9 million copies worldwide. Not only did it rejuvenate Americas love for video games but it also set the standard for user interface (D-pad style controller and platform games) and business model incorporating third party software developers.
The NES NTSC sound chip 2A03 was made by Ricoh. The NES board has five sound channels, two pulse wave, one triangle wave, one white noise and a sample channel.
The pulse channel (similar to the square wave) has volume control of sixteen levels and a variable duty cycle of 12.5%, 25%, 50%, 75%, with hardware pitch pending supporting frequencies from 54 Hz to 28 kHz. Pulse waves are commonly used as lead instruments because of the ability two combine the two channels into one lead sound. By playing two different notes to create a duophonic sound. Also playing the same notes or frequencies on both channels while one channel has a pitch bending effect assigned to it. This creates a duophonic sound and/or a sound similar to a synthesizers oscillator.
The triangle channel (similar to a sine wave) is a fixed volume and is capable of frequencies from 27 Hz to 56 kHz. Like the square wave. The triangle wave produces odd harmonics (as opposed to even harmonics), but because the triangles higher harmonics the roll off is much faster than the square wave (or pulse wave) which creates a sound closer to even harmonics, this could explain the pleasing sound a triangle has when used as lead instrument.
The noise channel produces white noise. White noise is a random flat signal that crosses over frequencies, also called spectral density.
White noise has the ability to cut through sound as well as absorbs other sounds (frequencies). The NES noise channel has sixteen-volume levels and has two modes. Each mode can be adjusted via the linear feedback shift register at sixteen programmed frequencies. In most music programs the linear feedback shift register is set to notes for example C4 D#5.
DPCM (info from Nocash NES Specs) The DPCM channel has six bits of range and uses 1-bit delta encoding at sixteen preprogrammed samples rates from 4.2 kHz to 33.5 kHz. This channel was also capable of playing standard pulse-code modulation (PCM) sound by writing individual 7bit values at timed intervals.