Editing Amiga (section)

==== Sound ====
The sound chip, named Paula, supports four [[PCM]] sound channels (two for the left speaker and two for the right) with 8-bit resolution for each channel and a 6-bit volume control per channel. The analog output is connected to a low-pass filter, which filters out high-frequency aliasing when the Amiga is using a lower sampling rate (see [[Nyquist frequency]]). The brightness of the Amiga's power LED is used to indicate the status of the Amiga's low-pass filter. The filter is active when the LED is at normal brightness, and deactivated when dimmed (or off on older A500 Amigas). On Amiga 1000 (and first Amiga 500 and Amiga 2000 model), the power LED had no relation to the filter's status, and a wire needed to be manually soldered between pins on the sound chip to disable the filter. Paula can read arbitrary waveforms at arbitrary rates and amplitudes directly from the system's [[RAM]], using direct memory access (DMA), making sound playback without CPU intervention possible.

Although the hardware is limited to four separate sound channels, software such as ''[[OctaMED]]'' uses software mixing to allow eight or more virtual channels, and it was possible for software to mix two hardware channels to achieve a single 14-bit resolution channel by playing with the volumes of the channels in such a way that one of the source channels contributes the most significant bits and the other the least.

The quality of the Amiga's sound output, and the fact that sound hardware is part of the standard chipset and easily addressed by software, were standout features of Amiga hardware unavailable on IBM PC compatibles for years.{{efn|The [[Gravis UltraSound]] expansion card got released in 1992 and became the first on the PC platform to feature multiple sample sound channels (up to 32) mixed in hardware from its own RAM.}} Third-party sound cards exist that provide [[Digital signal processor|DSP]] functions{{citation needed|date=March 2021}}, multi-track [[direct-to-disk recording]]{{citation needed|date=March 2021}}, multiple hardware sound channels and 16-bit and beyond resolutions. A retargetable sound API called [[AHI (Amiga)|AHI]] was developed allowing these cards to be used transparently by the [[Operating system|OS]] and software.<ref>{{cite magazine |last=Březovský|first=Boleslav |url=http://amigareview.amiga.sk/amiga-review-24/ahi-audio-system|date=January 1997|title=AHI Audio System|language=Czech|magazine=Amiga Review|publisher=Atlantida Publishing|issn=1211-1465|issue=24|pages=18–19}}</ref>