The Covox Speech Thing is an external audio device attached to the computer to output

digital sound Digital audio is a representation of sound recorded in, or converted into, digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical sampling (signal processing), s ...

. It was composed of a primitive 8-

bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...

DAC using a

resistor ladder A resistor ladder is an electrical circuit made from repeating units of resistors. Two configurations are discussed below, a string resistor ladder and an R-2R ladder. An R–2R ladder is a simple and inexpensive way to perform digital-to-analog ...

and an analogue signal output, and plugged into the

printer port In computing, a parallel port is a type of interface found on early computers (personal and otherwise) for connecting peripherals. The name refers to the way the data is sent; parallel ports send multiple bits of data at once ( paralle ...

of the PC. The Speech Thing was introduced on December 18, 1987 by Covox, Inc of

Eugene, Oregon Eugene ( ) is a city in the U.S. state of Oregon. It is located at the southern end of the Willamette Valley, near the confluence of the McKenzie and Willamette rivers, about east of the Oregon Coast. As of the 2020 United States Census, Eu ...

, for about US$70 (US$79.95 as of 1989), but as its parts were much cheaper than the complete plug, and as its design was fairly simple, people soon started to build their own variants. The plug was used long into the 1990s, as

sound card A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio i ...

s were still very expensive at that time. The plug was also quite popular in the

demoscene The demoscene is an international computer art subculture focused on producing demos: self-contained, sometimes extremely small, computer programs that produce audiovisual presentations. The purpose of a demo is to show off programming, visual ...

. An inherent problem of the design is that it requires very precise resistors. If normal parts are used, the values get shuffled, especially for quiet sounds, resulting in distortion. Nevertheless, the sound quality of the Covox plug is far superior compared to the

PC speaker A PC speaker is a loudspeaker built into some IBM PC compatible computers. The first IBM Personal Computer, model 5150, employed a standard 2.25 inch magnetic driven (dynamic) speaker. More recent computers use a tiny moving-iron or pie ...

; even today, a self-built Covox plug is still an inexpensive way to give old computers sound capabilities.

Commercial products

* Covox Speech Thing - the simplest hardware DAC, bundled with speech synthesis software, marketed originally as part of voice synthesis and recognition system. * Disney Sound Source - a hardware system with a similar design to the Covox Speech Thing, marketed by

Disney Software Disney Interactive Studios, Inc. was an American video game developer and publisher owned by The Walt Disney Company through Disney Interactive. Prior to its closure in 2016, it developed and distributed multi-platform video games and interact ...

in early 1990s. It consisted of 3 parts: a FIFO and a DAC on PCB plugged into printer port and separate amplifier / speaker box. Its price was set to only $14 and it was supported by many games (see below). It used external power (9 volt battery) and could be turned on/off by software. Contrary to the Speech Thing the output rate is determined by the hardware (7 kHz) and the design features a 16 byte FIFO allowing for autodetection and flow control of the output. In 2015 the hardware was reverse engineered so compatible circuits can be built from easily available off the shelf components. It is also emulated by the popular

DOSBox DOSBox is a free and open-source emulator which runs software for MS-DOS compatible disk operating systems—primarily video games. It was first released in 2002, when DOS technology was becoming obsolete. Its adoption for running DOS games i ...

emulator.

Features

In its simplest form, Covox received 8-bit, mono signal through the parallel port and produced analog output that could be amplified and played back on

loudspeaker A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or " ...

Sampling rate In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or spac ...

was not fixed by hardware means, and theoretically Covox can support any sampling rate. In practice, however,

parallel port In computing, a parallel port is a type of interface found on early computers (personal and otherwise) for connecting peripherals. The name refers to the way the data is sent; parallel ports send multiple bits of data at once ( parallel ...

speed limits make it rather hard to achieve even standard CD-quality 44100 Hz (the average

80286 The Intel 80286 (also marketed as the iAPX 286 and often called Intel 286) is a 16-bit microprocessor that was introduced on February 1, 1982. It was the first 8086-based CPU with separate, non-multiplexed address and data buses and also the fi ...

system could handle sampling rate for COVOX with 12kHz, the 486SX-33 system with 44kHz). Another limiting factor compared to traditional sound cards was the need to use computationally demanding timer interrupts to play background music, since there was no

direct memory access Direct memory access (DMA) is a feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU). Without DMA, when the CPU is using programmed input/output, it is t ...

available. However, the sound quality can be increased by software through

dithering Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and video data, and is often ...

, thus

aliasing In signal processing and related disciplines, aliasing is an effect that causes different signals to become indistinguishable (or ''aliases'' of one another) when sampled. It also often refers to the distortion or artifact that results when a ...

noise is minimized and the dynamics are increased (used in Inertia Player and

FastTracker 2 FastTracker 2 (also referred to as FastTracker II) is a music tracker A music tracker (sometimes referred to as just tracker for short) is a type of music sequencer software for creating music. The music is represented as discrete musical note ...

as an interpolating option).

Compatibility

Games

The Covox plug couldn't directly substitute any of the popular cards of that age (

AdLib Ad Lib, Inc. was a Canadian manufacturer of sound cards and other computer equipment founded by Martin Prevel, a former professor of music and vice-dean of the music department at the Université Laval. The company's best known product, the ''Ad ...

Sound Blaster Sound Blaster is a family of sound cards designed by Singaporean technology company Creative Technology (known in the US as Creative Labs). Sound Blaster sound cards were the de facto standard for consumer audio on the IBM PC compatible system pl ...

, Gravis Ultrasound, etc.), but several games / platforms supported it directly. It is also usually used in tandem with a AdLib sound card as said card officially was a music card and while it could be put into a mode to handle sampled audio, it could not play sampled audio and music at the same time. Notable entries include: * 688 Attack Sub - Title Music, Sound effects *

Zorro Zorro (Spanish language, Spanish for 'fox') is a fictional character created in 1919 by American pulp magazine, pulp writer Johnston McCulley, appearing in works set in the Pueblo of Los Angeles in Alta California. He is typically portrayed a ...

- plays Samples on Covox * Battle Bugs - plays Speech on Covox / requires EMS otherwise no Speech * Star Control 2 - Sounds *

Lemmings A lemming is a small rodent, usually found in or near the Arctic in tundra biomes. Lemmings form the subfamily Arvicolinae (also known as Microtinae) together with voles and muskrats, which form part of the superfamily Muroidea, which also include ...

– had special promotional edition named ''Covox Lemmings'', released with Covox sound cards; the game is identical to original game but contains a "Covox" level and seven more additional levels (only works with Covox Soundcards for ISA Bus). *

Pinball Fantasies ''Pinball Fantasies'' is a 1992 pinball video game originally developed by Digital Illusions and published by 21st Century Entertainment in Europe for the Amiga home computers. It is the sequel to ''Pinball Dreams'', which was released earlier i ...

. * Most older

Sierra Entertainment Sierra Entertainment, Inc. (formerly On-Line Systems and Sierra On-Line, Inc.) was an American video game developer and publisher founded in 1979 by Ken and Roberta Williams. The company is known for pioneering the graphic adventure game genre, ...

games, such as

King's Quest ''King's Quest'' is a graphic adventure game series, released between 1980 and 2016 and created by the American software company Sierra Entertainment. It is widely considered a classic series from the golden era of adventure games. Following th ...

and

Space Quest ''Space Quest'' is a series of six comic science fiction adventure games released between 1986 and 1995. The games follow the adventures of a hopeless janitor named Roger Wilco, who campaigns through the galaxy for "truth, justice and really cl ...

series, could output the sound to Covox when selecting "Disney Sound Source". * Some Games work with a software emulator called Virtual Soundblaster, such as

Wolfenstein 3D ''Wolfenstein 3D'' is a first-person shooter video game developed by id Software and published by Apogee Software and FormGen. Originally released on May 5, 1992, for DOS, it was inspired by the 1981 Muse Software video game ''Castle Wolfenstei ...

, has also native Support for the Disney Soundsource. * Others with the Tandy Emulator (TEMU) or Tandy 3 Voice Sound: Eye of the Beholder,

Sid Meier's Civilization ''Sid Meier's Civilization'' is a 1991 turn-based strategy 4X video game developed and published by MicroProse. The game was originally developed for MS-DOS running on a PC, and has undergone numerous revisions for various platforms. The pl ...

* Duke Nukem 3D, Redneck Rampage, Shadow Warrior supports Disney Sound Source.

Music trackers

Popular DOS-based trackers used on demoscene included Covox support, for example: * Modplay (also ModEdit, DMP, VP and other Mod players from early 1990s) (Up to 4 channel COVOX output or custom assembler routine for user device) * Inertia Player (mono, stereo-on-1 covox, with dithering option). * Multiplayer by DGS Italian Software Company * Galaxy Music Player (can play MODs even on an

Intel 8088 The Intel 8088 ("''eighty-eighty-eight''", also called iAPX 88) microprocessor is a variant of the Intel 8086. Introduced on June 1, 1979, the 8088 has an eight-bit external data bus instead of the 16-bit bus of the 8086. The 16-bit registers an ...

) *

Scream Tracker ''Scream Tracker'' is a tracker (an integrated multi-track step sequencer and sampler as a software application). It was created by Psi (Sami Tammilehto), one of the founders of the Finnish demogroup Future Crew. It was written in C and assembly ...

version 2.3 direct support. Version 3.21 through virtual-soundblaster driver. *

Fast Tracker FastTracker 2 (also referred to as FastTracker II) is a music tracker created by Fredrik "Mr. H" Huss and Magnus "Vogue" Högdahl, two members of the demogroup Triton (who later founded Starbreeze Studios) which set about releasing their own tra ...

(mono, stereo, stereo-on-1 mode, with dithering). *

Impulse Tracker Impulse Tracker is a multi-track music tracker ( music sequencer). Originally released in 1995 by Jeffrey Lim as freeware with commercial extensions, it was one of the last tracker programs for the DOS platform. In 2014, on its 20th anniversary, ...

Emulators

Emulator In computing, an emulator is Computer hardware, hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run so ...

s existed that allowed Covox to act as if there was another soundboard installed: * Virtual SoundBlaster - could emulate Sound Blaster on Covox * Covoxer - could emulate

Tandy 1000 The Tandy 1000 is the first in a line of IBM PC workalike home computer systems produced by the Tandy Corporation for sale in its Radio Shack and Radio Shack Computer Center chains of stores. Overview In December 1983, an executive with Tandy C ...

2000 File:2000 Events Collage.png, From left, clockwise: Protests against Bush v. Gore after the 2000 United States presidential election; Heads of state meet for the Millennium Summit; The International Space Station in its infant form as seen from ...

music synthesizer * TEMU - could emulate

music synthesizer and DSS In reverse, the

and Fake86 emulators allow to emulate presence of Covox (as Disney Sound Source) on a machine without such physical device connected. As of 2015 the circuit for the Disney Sound Source has been reverse engineered, so Covox plugs can be used with software requiring such hardware without the need of any additional software emulators using an additional plug that goes between the computer's LPT port and the Covox.

Operating systems

Several operating systems have a driver for Covox available for install: *

Windows 3.1x Windows 3.1 is a major release of Microsoft Windows. It was released to manufacturing on April 6, 1992, as a successor to Windows 3.0. Like its predecessors, the Windows 3.1 series ran as a shell on top of MS-DOS. Codenamed Janus, Windows 3. ...

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of operating systems. The first operating system in the 9x family, it is the successor to Windows 3.1x, and was released to manufacturin ...

Windows 98 Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. The second operating system in the 9x line, it is the successor to Windows 95, and was released to ...

* Linux 2.1 *

MenuetOS MenuetOS is an operating system with a monolithic preemptive, real-time kernel written in FASM assembly language. The system also includes video drivers. It runs on 64-bit and 32-bit x86 architecture computers. Its author is Ville M. Turjanma ...

CSI-DOS CSI-DOS is an operating system, created in Samara, for the Soviet Elektronika BK-0011M and Elektronika BK-0011 microcomputers. CSI-DOS did not support the earlier BK-0010. CSI-DOS used its own unique file system and only supported a color gr ...

A userspace program that uses direct access to the hardware can also be used on modern Linux distributions.

Modern clones

* Simple LPTsnd - * CVX-4 - * Disney Soundsource Remake - * Benedikts Covox Remakes (SoundJr, Covox Replica, FTL Soundadapter) - * ISA LPT DAC r0 (Covox Clone connected to ISA BUS) -

References

External links

Powering devices from PC parallel port
an article on LPT-port devices, including Covox.
List of games that support Disney Sound Source
at MobyGames.com.
List of games that support Covox Speech Thing
at MobyGames.com.
A collection of software for Covox
including Windows driver. *
Covox Voice Master schematics and software
*
Covox Digital-Analog Converter
a comprehensive Covox history overview.
DSS Reverse Engineering on Vogons
DSS Reverse Engineering Thread {{PC sound standards Sound cards Computer-related introductions in 1986