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# Generating audio signals
In order to generate sound for this project, a few posibilities exist (see chapters below)
## Sound chips
A sound chip is made to use digital, analog or mixed signals and produce a tone or sound based on that.
| Manufacturer | Chip | Year | Channels | Stand-alone | Cost/availability |
| ------------------ | ------------------------------------------------------------------------------------------------------------- | ---- | -------- | ----------- | ----------------- |
| Atari, Inc. | [POKEY](https://en.wikipedia.org/wiki/POKEY) | 1979 | 4 | Somewhat | N/A |
| General Instrument | [AY-3-8910](https://en.wikipedia.org/wiki/AY-3-8910) | 1978 | 3 | Yes | N/A |
| General Instrument | [SP0250](https://en.wikipedia.org/wiki/General_Instrument_SP0256) | 1981 | 1 | Yes | N/A |
| Konami | [VRC6](https://en.wikipedia.org/wiki/VRC6) | 1987 | 3 | Yes | N/A |
| Philips | [Philips SAA1099](https://en.wikipedia.org/wiki/Philips_SAA1099 "Philips SAA1099") | 1984 | 6 | Yes | N/A |
| Sunsoft 5B | [Sunsoft 5B](https://en.wikipedia.org/wiki/Memory_management_controller#FME-7 "Memory management controller") | 1992 | 3 | Yes? | N/A |
| Texas Instruments | [SN76477](https://en.wikipedia.org/wiki/SN76477) | 1978 | 1 | Yes | N/A |
| Texas Instruments | [SN76489](https://en.wikipedia.org/wiki/SN76489 "SN76489") | 1980 | 4 | Yes | N/A |
| Texas Instruments | [Sega PSG (SN76496)](https://en.wikipedia.org/wiki/SN76496 "SN76496") | 1982 | 4 | Yes | N/A |
This chart shows different audio chips that might have been used in retro consoles. While all of them aren't easily available anymore it is still interesting to take a close look at how these IC's (Intergrated Ciruit) work.
Most chips work on one of two pricibles, this being either a "Programmable sound generator" or "Sound Chip"
### Programmable sound generator (PSG)
PSG's are a subset of sound chips that generate sound based on a set of pre programmed tones they can generate. For example, this can be done by: modulating a input square wave to a different frequency and or amplitude.
### Pulse-code modulation
Pulse-code modulation uses pre-sampled data to generate sounds. This causes a lot more work for the engineer before gaining a working system. The flip side of that coin is that the Output can be of a better quality (depending on the sampled audio used).
## FPGA Circuit
|