1. DAC Encoding
More than a mere bitcrusher
chipcrusher’s DAC Encoding does the following passes on the input sound:
- Resamples the input audio input from the host’s samplerate to a user specified ‘virtual’ samplerate.
- Encodes/decodes that data by using specified techniques. (See “The Encodings” section below)
- Change the weighting of bits in the DAC to emulate non-monotonic behavior.
- Oversamples the decoded data to mimic the behavior of specific DACs. (Zero-Order Hold, PWM, etc)
- Applies basic filtering: one pole low pass (RC Filter) and high pass (AC Coupling)
- Finally it downsamples the result back into the output host samplerate.
- LPCM (Linear pulse-code modulation):
Examples: Compact Disc (if 16bit/44.1kHz), E-Mu SP12 (12bit/27.5kHz) E-Mu SP1200 (12bit/26.04kHz)
- FPCM (Floating-point pulse-code modulation):
Example: The YM301X series DAC used for Yamaha’s 4OP FM synthesizers encoded audio on 10.3 bits.
- DPCM (Differential pulse-code modulation):
Example: Delta modulation channel provided by the RP2A03/RP2A07 CPUs used in the Big N’s 8bit console uses Bits=6 and Parameter=1
- A-Law and μ-Law:
Examples: Early US samplers and drum machines which used AM6070/AM6072 ICs like the LINN Drum machines, and the E-MU Emulator I/II/Drumulator.
Example: MSM(OKI)6295 Used in LOTS of late 80′s and early 90′s arcade titles (All non Q-sound CPS1 titles)
- BRR (Bit Rate Reduction)
Example: S_ny’s specific ADPCM Encoding used in the S-DSP of the SNES.
- YADPCM :
Examples: N’s ‘Oui-mote’ and various Yamaha FM chips for sample playback.
Example: Speak & Spell
- PWM (Pulse-width modulation):
Examples: Some legacy software on the Apple II SoftDAC (3 and 4 bit versions) and DAC522. You will find that they are NASTY sounding. You have been warned.
- PDM (Pulse-density modulation):
This is usually run at VERY high sample rates, (SACD/DSD uses 2.8224 MHz, but since here we only have straight PCM for input, whose rate depend on the host rate (typically 44/48/96kHz), it is quite useless to use PDM at higher frequency, since we don’t have extra information to encode in time.
2. BACKGROUND NOISE
Noises were carefully recorded and looped from our collection of gear (consoles and arcade boards) which were also used for the research behind chipsounds. Just select the preset and adjust volume to taste. Note: default volumes should be used if you want to keep it subtle.
Some units generate different noises depending on external factors, for instance, it is well known that the Commodore 64 and Vectrex background noises were directly related to what was displayed at a particular time on the screen. In this case various noises are available.
- Atari: 2600, STf, 800XL
- Bally Astrocade
- C64: Brown breadbox, C64C with 8580, through the RF
- GameBoy: (DMG-1), Color (CGB)
- Gemini (Atari 2600 clone)
- Genesis 1 (using headphones – two levels), using the audio out, and the RF modulator
- Intellivision: I (RF), III (RF)
- Leisure Vision
- NES and VS arcade PCB
- Casio PV1000 RF (good luck finding your own :)
- Sega Master System (RCA and RF)
- Super PacMan arcade PCB
- Vectrex (4 different display patterns)
How does it work?
A very efficient convolution engine allows chipcrusher’s sound (which can be very harsh at times) to go through a few of the most well loved vintage gaming devices, computers or monitors. Each impulse gives a totally different tonal quality to the sound.
The available impulses are split into 5 categories.
Speaker and Casings impulses of various PC clones but also three Apple classics, the Apple IIe and the Apple IIGS.
Mostly filled with the 3 variants of AMIGA Original Chip Set machines (A500, A1000 and A2000), with the infamous LED filters on and off. We also included the extreme lowpass filter from the SK1.
From the classic Commodore monitors used with the C64, to the Mac Plus and even a 50s Television set.
Most portable gaming devices, or speaker-bearing devices of the day including a Coleco Mini-Arcade, and a fullsize Galaxian Arcade Cabinet and Nintend_ VS cabinet. A Oui-Mote, a Vectrex, 4 different gameboy’s (DMG-1, CGB, GBA and GBA clam shell) and more!
Various classic drum machines, keyboards who came with a speaker.