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AdLib, CMS & Sound Blaster¶

For many who owned a gaming PC in the 1990s, the name Sound Blaster is a synonym for “sound card” — and rightly so, as the Sound Blaster family of cards by Creative Technology was the de facto standard for DOS gaming. The first Sound Blaster was released in 1989, and it quickly became the best-selling expansion card for the PC. Virtually all games from 1990 onwards had Sound Blaster support in some shape or form, and this remained unchanged for the rest of the DOS-era until the late 90s.

DOSBox can emulate all major revisions of the Sound Blaster family. One of the most common models was the Sound Blaster 16 which has good (but not perfect) backward-compatibility with earlier cards. This is the sound card DOSBox emulates by default to ensure the widest possible compatibility with games,

Most games that support the AdLib or Sound Blaster work fine with the DOSBox defaults, and don’t require you to load any DOS drivers. A small percentage of games, however — especially from the early Sound Blaster days — only work with a specific model, or require a driver to be loaded. Please refer to the List of games that require a sound driver on the wiki for further details.

Sound Blaster overview¶

On-board synthesisers¶

In addition to their digital audio playback capabilities (also referred to as PCM sound), all Sound Blaster models feature at least one on-board synthesiser for the generation of music and sound effects. The most important of these is the AdLib that is present on all Sound Blaster cards. The AdLib is also referred to as OPL sound (after the Yamaha OPL range of chips responsible for the “AdLib sound”), or FM sound (after the OPL chip’s FM sound synthesis capabilities). DOSBox uses the highly accurate NukedOPL library to achieve a nearly bit-perfect emulation of the OPL chips.

The other less common synthesiser is the Creative Music System (also referred to as C/MS, or CMS) which is only present on the earliest Sound Blaster models.

Because the history and even the emulation of these synthesisers are so closely entwined with those of the Sound Blaster, we are going to discuss them together.

Emulated Sound Blaster models¶

The below table lists all Sound Blaster models emulated by DOSBox, along with their main capabilities:

Model sbtype value Digital audio Synthesiser
Game Blaster gb N/A CMS (stereo)
Sound Blaster 1.0 sb1 8-bit mono 23kHz OPL2 (mono)
CMS (stereo)
Sound Blaster 2.0 sb2 8-bit mono 23kHz OPL2 (mono)
CMS (stereo)
Sound Blaster Pro sbpro1 8-bit mono 44kHz
8-bit stereo 23kHz		 Dual OPL2 (stereo)
Sound Blaster Pro 2.0 sbpro2 8-bit mono 44kHz
8-bit stereo 23kHz		 OPL3 (stereo)
Sound Blaster 16 sb16 16-bit stereo 44kHz OPL3 (stereo)

Mixer channels¶

The digital audio of the Sound Blaster is output to the SB mixer channel, while the AdLib (OPL) synthesiser has its own dedicated OPL channel. Both channels can be either mono or stereo, depending on the particular Sound Blaster model being emulated.

The Creative Music System synthesiser has its own dedicated CMS channel, which is always stereo.

The upshot of this is that the digital audio and synthesiser volumes can be adjusted independently via the DOSBox mixer (e.g., in games that use digital audio for speech and sound effects, and the synthesiser for music).

Note

Starting with the Sound Blaster Pro, programs can adjust the volume of the digital audio, OPL, and CD Audio channels via the Sound Blaster software mixer. By default, DOSBox forwards these adjustments to the DOSBox mixer, allowing programs to change the volumes of these channels. This can potentially result in your manually set volumes being overridden. To prevent this from happening, set the sbmixer configuration setting to off.

Default settings¶

The default Sound Blaster settings shown below have been selected for the widest possible compatibility with games. Most games can auto-detect the presence of a Sound Blaster card and these settings, but in case they need a little help, here are the values to use:

Setting Config setting Default value
Base address (or I/O address, or port) sbbase 220
IRQ (or interrupt) irq 7
DMA (or low DMA) dma 1
High DMA (or HDMA) hdma 5

If you have configured a game for Sound Blaster speech and music but can’t hear both or maybe there is no sound at all, or if the game hangs or crashes, first double check that the above settings have been set in the game’s configuration. Many games don’t let you to set all of them manually and just assume some common fixed values instead. Please refer to the detailed description of the config settings for troubleshooting tips.

Selecting the best Sound Blaster model for a game¶

DOSBox emulates the Sound Blaster 16 by default to ensure the widest overall compatibility with DOS games. This lowest common denominator setting will serve you well if you just want to play some games with minimum hassle. If that’s the case, you might as well stop reading this chapter now, and only come back to it if you’ve encountered issues with certain titles, or if you want to further your understanding of the subtler differences between the various Sound Blaster models.

For the audio enthusiasts who are still with us, here’s the thing: if you want to coax the best sound out of a particular game, often you’ll need to select a specific Sound Blaster model the game was primarily developed for. Although the Sound Blaster 16 is compatible with earlier models, this compatibility is imperfect and is plagued by a range of issues:

Stereo bug
Due to a design flaw, games with support for stereo digital audio on Sound Blaster Pro output mono sound only on the Sound Blaster 16.
Different analog low-pass output filters

Sound Blaster cards before the Sound Blaster 16 have a fixed frequency low-pass filter on the output to reduce the effects of aliasing which sounds like metallic overtones when playing digital audio at low sample rates.

This fixed filter was changed to a variable-frequency design on the Sound Blaster 16, and the character of the filter was also altered. The old filter let a good amount of the metallic overtones through, resulting in a characteristic gritty, crunchy sound, while the new variable brick-wall filter was much more effective at reducing these overtones.

The result is that low sample rate digital audio typical to earlier DOS games sounds overly muffled on the Sound Blaster 16 compared to earlier models.

Dual OPL2 support
The Sound Blaster Pro 1.0 is capable of stereo “dual OPL2” operation thanks to its two on-board OPL2 chips. This is the only Sound Blaster model with a dual OPL2 configuration. Previous models feature a single OPL2 chip that can output mono sound only, and later cards have the improved OPL3 chip that can also output stereo. Stereo sound on dual OPL2 and OPL3 needs to be programmed differently, and some games were targeting only one of these two incompatible stereo OPL modes. Therefore, games that were written for dual OPL2 will only produce stereo synthesised sound on the Sound Blaster Pro 1.0 and no other model.

To provide a good out-of-the-box experience that works well enough with most games without tinkering, DOSBox defaults to the imaginary modern filter setting on all Sound Blaster models. This implements simple linear-interpolation instead of accurately emulating the analog output filter — this makes most games sound decent regardless of the Sound Blaster model in use, but it’s not authentic.

For the best authentic results, set the most appropriate Sound Blaster model for each game via the sb_type configuration setting. Additionally, set the sb_filter setting to auto to let DOSBox select the output filter appropriate for the emulated Sound Blaster model.

For example, use the following settings to enable authentic Sound Blaster Pro 1.0 emulation with dual OPL2 support:

[sblaster]
sbtype = sbpro1
sb_filter = auto

Determining the best Sound Blaster model for a game can be tricky as the different cards were released very close to each other; simply looking at the game’s release date often doesn’t help much. Ultimately, you’ll need to do a little bit of research, experiment, and trust your ears.

Creative Music System (CMS) / Game Blaster¶

The Creative Music System (also referred to as CMS or C/MS) was released in August 1987 by Creative Technology. This was the first sound card of the company, it sounded like a much simpler variant of the AdLib card, and it did not sell that well.

The card was rebranded as Game Blaster a year later, without making any changes to the hardware.

Use the following setting to enable Game Blaster emulation:

[sblaster]
sbtype = gb

Note

As the CMS is also present on the Sound Blaster 1.0, and optionally on the Sound Blaster 2.0, CMS support in some early games might only work with either the Game Blaster or one of the Sound Blaster models, but not both.

FM synthesisers¶

AdLib Music Synthesizer Card¶

The AdLib Music Synthesizer Card (typically simply referred to as AdLib) was released by Ad Lib in 1987. It was the first popular sound card for IBM PC compatibles, capable of producing multichannel music and sound effects via its Yamaha OPL2 synthesizer chip.

Being such a huge step up from the PC speaker, the AdLib took the market by storm. As it quickly became a de facto standard, many competing sound card manufacturers started including full AdLib compatibility on their cards. The result of this is that virtually all DOS games from 1990 onwards support the AdLib, at least as a fallback option.

Digital audio is not supported on the card, but some games were able to approximate it with various tricks (e.g., F-15 Strike Eagle II by MicroProse).

Use the following settings to enable AdLib (OPL2) emulation:

[sblaster]
sbtype = none
oplmode = opl2

Note

When oplmode is set to opl2, CMS emulation is always enabled as well. This is legacy DOSBox behaviour, and will be addressed in a future version.

AdLib Gold 1000¶

The AdLib Gold 1000 was released in 1992. It has a Yamaha OPL3 chip and a stereo audio processor on-board, and it also supports 12-bit digital audio. An optional surround module is available to add further spatial effects to the OPL output (e.g., chorus and reverb).

DOSBox fully emulates the card, including the surround module, except for the digital audio capabilities.

Very few games have direct support for the AdLib Gold 1000, and no known game makes use of its digital audio features. The single game in existence that really takes advantage of the AdLib Gold and its surround module is the adventure game Dune from 1992.

Use the following settings to enable AdLib Gold 1000 emulation. Typically, you would use the card together with a Sound Blaster for digital audio. The setup utility of Dune should auto-detect AdLib Gold and the surround module correctly with these settings.

[sblaster]
sbtype = sb16
oplmode = opl3gold

ESS Enhanced FM Audio (ESFM)¶

ESFM is the OPL3-compatible FM synthesiser found on later ESS AudioDrive cards. In “legacy mode”, ESFM is fully compatible with the Yamaha OPL3 and yields almost identical output on most material. What sets it apart is its “native mode”, which offers advanced synthesis features surpassing the OPL3’s capabilities — it bridges the gap between synthetic-sounding OPL music and sample-based MIDI music.

Since ESFM was released in 1995, only a handful of games support native mode, but in the few that do, the results sound quite spectacular.

  • To run ESFM in legacy mode, use oplmode = esfm with any Sound Blaster model and configure the game for Sound Blaster and AdLib/OPL as usual.

  • To use native mode, set sbtype = ess and configure the ESS Technology ES1688, ES1788, ES1888 Enhanced FM Audio MIDI music driver in the game’s setup utility (most games that support ESFM natively use the Miles Sound System). For the digital audio driver, select the Sound Blaster Pro option (ESS AudioDrive cards are Sound Blaster Pro compatible).

[sblaster]
sbtype = ess
Games with ESFM support

Tip

You can also try to “retrofit” the ESFM.MID driver from Miles Sound System games that have it into earlier ones that don’t. For example, Discworld sounds great with the ESFM driver from Heaven’s Dawn.

Sound Blaster models¶

Sound Blaster 1.0¶

The original Sound Blaster 1.0 was released by Creative Technology in 1989 as the successor of their Game Blaster card. It was the first sound card on the market to have digital audio playback capabilities; it could output 8-bit digital audio at up to 23kHz sample rates on a single mono channel. Full compatibility with the CMS and the AdLib (Yamaha OPL2) played a critical role in the card’s enormous success. In less than a year, the Sound Blaster became the best-selling expansion card for the PC.

This had transformed DOS gaming, as games could use realistic digital audio effects while simultaneously playing music via the OPL2 or CMS synthesiser chips.

Use the following setting to enable Sound Blaster 1.0 emulation:

[sblaster]
sbtype = sb1

Note

Certain games from the early Sound Blaster days might only work with the Sound Blaster 1.0 and no other models.

Sound Blaster 2.0¶

The Sound Blaster 2.0 was released by Creative Technology in October 1991. Similarly to its predecessor, the Sound Blaster 1.0, it can play back 8-bit digital audio on a single mono channel, but the maximum sample rate has been increased to 44kHz.

The card retains the perfect AdLib (OPL2) compatibility, but CMS support was only available as an optional add-on. Some early games specifically written for Sound Blaster 1.0 might have problems with this or later cards.

Use the following setting to enable Sound Blaster 2.0 emulation:

[sblaster]
sbtype = sb2

Sound Blaster Pro¶

The Sound Blaster Pro (retroactively also referred to as Sound Blaster Pro 1.0) was released by Creative Technology in May 1991. This was the first model that introduced stereo sound into the Sound Blaster lineup. It is backward-compatible with earlier models, but in addition to 8-bit mono playback of digital audio at up to to 44kHz, it’s also capable of stereo 8-bit output at a maximum of 23kHz. A distinctive feature of the card is a pair of on-board Yamaha OPL2 chips to support stereo synthesised sound.

This is the only Sound Blaster model with such a dual OPL2 configuration; many games take advantage of it and output stereo OPL music when configured for the Sound Blaster Pro.

Use the following setting to enable Sound Blaster Pro emulation:

[sblaster]
sbtype = sbpro1

Important

Games with stereo OPL sound are usually targeting either the dual OPL2 equipped Sound Blaster Pro 1.0, or the OPL3 chip of later models (OPL3 is capable of stereo sound in a single chip). It is important to configure these games for the appropriate Sound Blaster model via the sbtype setting, and select the same model in the game’s sound setup. Failing to do so will produce mono OPL sound at best, or no sound at all at worst.

Note

This is the only card supported by the known OEM releases of Microsoft Windows 3.0a with Multimedia Extensions.

Games with dual OPL2 stereo music

The following games are known to support stereo dual OPL2 music when configured for the Sound Blaster Pro (sbtype = sbpro1). Select “Sound Blaster Pro” (or just “Sound Blaster” in some cases) in the game’s sound setup to hear stereo OPL.

  • 11th Hour, The
  • Amberstar
  • Azrael’s Tear
  • B-17 Flying Fortress
  • Battle Isle 2200
  • BattleTech: The Crescent Hawks’ Revenge
  • Blackthorne
  • Body Blows
  • Castle of Dr. Brain
  • Cobra Mission
  • Command Adventures: Starship
  • Conquests of the Longbow
  • Darklands
  • David Leadbetter’s Greens
  • Death Gate
  • Der Clou (The Clue!)
  • Discworld
  • Dragonsphere
  • Dune II
  • Dungeon Master II
  • EcoQuest: The Search for Cetus
  • Elvira: Mistress of the Dark
  • F-117A Nighthawk Stealth Fighter 2.0
  • F-15 Strike Eagle III
  • Fleet Defender
  • Formula One Grand Prix
  • Gobliins 2
  • Gods
  • Golden Axe
  • Gunship 2000
  • Harrier Jump Jet
  • Heroes of Might and Magic 2
  • Hi-Octane
  • Hocus Pocus
  • Hoyle’s Official Book of Games Volume 3
  • Indiana Jones and the Fate of Atlantis
  • Inherit The Earth: Quest For The Orb
  • Jill of the Jungle
  • Jones in the Fast Lane
  • King’s Quest V
  • Knights of Xentar
  • Legend of Kyrandia
  • Leisure Suit Larry 1 VGA
  • Leisure Suit Larry 5
  • Leisure Suit Larry 6
  • Lord of the Rings Volume 1
  • Lord of the Rings Volume 2
  • Master of Magic
  • Master of Orion
  • Mixed-Up Mother Goose
  • Mixed-Up Fairy Tales
  • Pirates! Gold
  • Police Quest III
  • Prince of Persia 2
  • Quest for Glory II
  • Quest for Glory IV
  • Return of the Phantom
  • Settlers II, The
  • Sid Meier’s Civilization
  • Sid Meier’s Colonization
  • Sid Meier’s Railroad Tycoon Deluxe
  • Silpheed
  • Space Quest I VGA
  • Space Quest III
  • Space Quest IV
  • Special Forces
  • Star Wars: Dark Forces
  • Stone Age
  • Street Fighter II
  • Strike Commander
  • Stronghold
  • Summer Challenge
  • Supaplex
  • System Shock
  • Theme Hospital
  • Ultima Underworld
  • Ultima Underworld II
  • William Shatner’s TekWar
  • Wing Commander
  • Winter Challenge
  • Witchhaven
  • Witchhaven II
  • Wolf
  • X-Com: UFO Defense
  • Xatax
  • Z

Sound Blaster Pro 2.0¶

The Sound Blaster Pro 2.0 was released by Creative Technology in 1991, quickly replacing its predecessor, the Sound Blaster Pro.

It is functionally the same as the earlier Sound Blaster Pro with one key difference: instead of the dual OPL2 chips, it sports a single Yamaha OPL3 chip also capable of producing stereo sound. The OPL3 has perfect backward compatibility with the single-OPL2 configuration of earlier cards, but not with dual OPL2.

Use the following setting to enable Sound Blaster Pro 2.0 emulation:

[sblaster]
sbtype = sbpro2

Important

Games with stereo OPL sound are usually targeting either the dual OPL2 equipped Sound Blaster Pro 1.0, or the OPL3 chip of later models, such as the Sound Blaster Pro 2.0 (OPL3 is capable of stereo sound in a single chip). It is important to configure these games for the appropriate Sound Blaster model via the sbtype setting, and select the same model in the game’s sound setup. Failing to do so will produce mono OPL sound at best, or no sound at all at worst.

Games with OPL3 stereo music

The following games are known to support OPL3 stereo music. Configure the game for the Sound Blaster Pro 2.0 (sbtype = sbpro2) or Sound Blaster 16 (sbtype = sb16) to hear stereo OPL3 output.

  • Cybersphere
  • Dark Forces
  • Darklands
  • Descent
  • Descent 2 (if CD audio is disabled)
  • Doom (requires SET DMXOPTION=-phase -opl3 in the autoexec)
  • Doom 2 (requires SET DMXOPTION=-phase -opl3 in the autoexec)
  • Dune (on AdLib Gold)
  • Dungeon Master 2
  • Fleet Defender
  • FlixMix
  • Gabriel Knight
  • Hexen (requires SET DMXOPTION=-phase -opl3 in the autoexec)
  • King’s Quest VI
  • Lost Vikings, The
  • Magic Carpet 2
  • Sam & Max Hit the Road
  • Settlers II, The
  • Sid Meier’s Civilization (requires updated sound drivers)
  • SimCity 2000
  • SlipSpeed
  • Stonekeep
  • System Shock
  • Tetris Classic
  • Theme Hospital
  • TIE Fighter
  • WarCraft II
  • Xatax

Sound Blaster 16¶

The Sound Blaster 16 was released by Creative Technology in June 1992. This is the first Sound Blaster card to support CD-quality sound (stereo 16-bit digital audio at 44kHz sample rate). The card features the Yahama OPL3 chip that has perfect backward-compatibility with OPL2 (but not dual OPL2), and supports stereo operation in a single chip.

DOSBox emulates the Sound Blaster 16 by default. Most games either support this card directly, or will work with selecting an earlier Sound Blaster model in the game’s setup, making use of the card’s backward-compatibility feature. This is a good overall default, but if you’re an audio enthusiast or would just like to get the best possible experience out of a given game, reading the Selecting the best Sound Blaster model for a game section is highly recommended.

Use the following setting to enable Sound Blaster 16 emulation:

[sblaster]
sbtype = sb16
Games with true 16-bit digital audio

While most games advertised Sound Blaster 16 support, the majority only played back 8-bit samples due to floppy disk storage constraints. Starting around 1995, CD-ROM titles began incorporating genuine 16-bit recordings, typically at 22 kHz. The jump from 8-bit to 16-bit is noticeable primarily as reduced background noise; the higher sampling rate often matters more to the perceived audio quality than the bit depth alone.

The following games are known to use true 16-bit digital audio with the Sound Blaster 16 (sbtype = sb16):

  • AH-64D Longbow
  • Blood
  • Command & Conquer
  • Command & Conquer: Red Alert
  • Crusader: No Remorse
  • Crusader: No Regret
  • Descent II
  • Duke Nukem 3D
  • Dungeon Keeper
  • EcoQuest 2
  • Eradicator
  • Fade to Black
  • Freddy Pharkas
  • FX Fighter
  • Gabriel Knight
  • Gabriel Knight 2
  • Hi-Octane
  • King’s Quest VII
  • Leisure Suit Larry 6
  • M.A.X.
  • Mission Critical
  • Pepper’s Adventures in Time
  • Police Quest IV
  • Quake
  • Quest for Glory IV
  • Rise of the Triad
  • Shadow Warrior
  • Shattered Steel
  • Slater and Charlie Go Camping
  • Space Quest 6
  • Star Trek: The Next Generation
  • Torin’s Passage
  • Under a Killing Moon
  • The Pandora Directive
  • Wing Commander III
  • Wing Commander IV

Configuration settings¶

Due to their tightly coupled nature, all AdLib, Creative Music System (CMS), Game Blaster and Sound Blaster settings are to be configured in the [sblaster] section.

Sound Blaster¶

Many DOS programs use the BLASTER DOS environment variable to auto-detect and auto-configure the Sound Blaster card. On a real machine, this variable is set up in AUTOEXEC.BAT during the Sound Blaster driver installation process.

DOSBox injects the BLASTER environment variable at startup based on the card’s configuration in the [sblaster] section. You should never set this variable manually.

To view the value of the variable, execute the SET BLASTER DOS command. For example, this is the output you’ll get with the default settings:

BLASTER=A220 I7 D1 H5 T6

The meaning of the space-separated values are as follows:

  • Axyz — base address (sbbase)
  • Ix — IRQ number (irq)
  • Dx — DMA channel (dma)
  • Hx — High DMA channel (hdma)

The number after the T parameter describes the type of the card:

  • 1 – Sound Blaster 1.x
  • 2 – Sound Blaster Pro
  • 3 – Sound Blaster 2.x
  • 4 – Sound Blaster Pro 2
  • 5 – Sound Blaster Pro MCA — not used by DOSBox
  • 6 – Sound Blaster 16, 32, AWE32/64, or ViBRA
  • 10 – Sound Blaster MCA — not used by DOSBox
dma¶

The DMA (also referred to as low DMA) channel used for 8-bit digital audio on the Sound Blaster.

Possible values: 0, 1 default, 3, 5, 6, 7.

You can typically only choose between 0, 1 and 3 on real cards.

Important

Many earlier games assume DMA 1 and do not let the user to change it, making it the most compatible setting.

hdma¶

The high DMA channel used for 16-bit digital audio on the Sound Blaster 16.

Possible values: 0, 1, 3, 5 default, 6, 7.

You can typically only choose between 5, 6 and 7 on real cards.

irq¶

The IRQ (interrupt) number of the Game Blaster / Sound Blaster.

Possible values: 3, 5, 7 default, 9, 10, 11, 12.

You can typically only choose between 3, 5, 7 and 10 on real cards,

Many games do not recognize IRQs higher than 7.

Important

Cards before the Sound Blaster 16 defaulted to IRQ 7. From the Sound Blaster 16 onwards, the default had been changed to IRQ 5. Because of this, many earlier games assume IRQ 7 and do not let the user to change it. Games that assume IRQ 5 are rarer, making 7 the overall most compatible setting.

sb_filter¶

Filter settings for the Sound Blaster digital audio output:

  • auto – Use the appropriate filter determined by the sbtype setting.
  • sb1, sb2, sbpro1, sbpro2, sb16 – Use the digital audio filter of this Sound Blaster model.
  • modern default – Use linear interpolation upsampling regardless of the sbtype setting. This is the legacy DOSBox behaviour; it acts as a sort of a low-pass filter. Use auto instead to enable model-authentic filter emulation.
  • off – Don’t filter the digital audio output.
  • <custom> – Custom filter definition; see Custom filter settings for details.

These are the model specific low-pass filter settings for the digital audio output:

sbtype Filter type Cutoff frequency
sb1 2nd order (12dB/oct) 3.8kHz
sb2 2nd order (12dB/oct) 4.8kHz
sbpro1
sbpro2		 2nd order (12dB/oct) 3.2kHz
sb16 brickwall variable;
half of the playback rate
sb_filter_always_on¶

Force the Sound Blaster Pro 2 filter to be always on. Other Sound Blaster models don’t allow toggling the filter in software.

Possible values: on, off default

sbbase¶

The base address (also referred to as I/O address, or port) of the Game Blaster / Sound Blaster.

Possible values: 220 default, 240, 260, 280, 2a0, 2c0, 2e0, 300.

You can typically only choose between 220, 240 and 260 on real cards.

The AdLib Music Synthesizer Card has a fixed base address of 380 that cannot be changed. Games can access the Yamaha OPL chip on Sound Blaster cards either at base address 380 (this is the AdLib compatibility mode), or at the Sound Blaster’s base address.

Important

Virtually all games with Game Blaster / Creative Music System (CMS) support only work with the base address set to 220. A significant number of early 90s games with Sound Blaster support also assume a base address of 220 and do not let the user the change it, making this the most compatible setting.

sbmixer¶

Allow the Sound Blaster mixer to modify the DOSBox mixer.

Possible values: on default, off

Starting with the Sound Blaster Pro, programs can adjust the volume of the digital audio, OPL, and CD Audio channels via the Sound Blaster software mixer. By default, DOSBox forwards these adjustments to the DOSBox mixer which can potentially result in your manually set volumes being overridden. To prevent this from happening, set the sbmixer configuration setting to off to retain full manual control over the channel volumes. Note that this might break some games that use the mixer to achieve certain effects (e.g., dynamically lowering the music volume when voice-overs are playing).

sbtype¶

Sound Blaster model to emulate.

Possible values:

Please refer to the Emulated Sound Blaster models section for an overview of the capabilities of the different models.

sbwarmup¶

Silence initial digital audio after card power-on for this many milliseconds.

Default value: 100

This mitigates pops heard when starting many Sound Blaster based games. Reduce this if you notice intial playback is missing digital audio.

OPL¶

Note

Some games trigger low-level residual noise from the OPL synth in quiet passages. The Denoiser removes this without degrading sound quality.

opl_fadeout¶

Fade out hanging notes on the OPL synth.

Possible values:

  • off default – Don’t fade out hanging notes.
  • fade – Fade out hanging notes. You should only enable this in games that sometimes play hanging notes that never stop (e.g., Bard’s Tale).
  • <custom> – A custom fade-out definition in the following format: WAIT FADE, where WAIT is how long after the last I/O port write fading begins (between 100 and 5000 milliseconds), and FADE is the fade-out period (between 10 and 3000 milliseconds). Examples:
    • 300 200 (wait 300 ms before fading out over a 200 ms period)
    • 1000 3000 (wait 1 second before fading out over 3 seconds)
opl_filter¶

Filter settings for the OPL output:

  • auto default – Use the appropriate filter determined by the sbtype setting.
  • sb1, sb2, sbpro1, sbpro2, sb16 – Use the OPL filter of this Sound Blaster model.
  • off – Don’t filter the OPL output.
  • <custom> – Custom filter definition; see Custom filter settings for details.

These are the model specific low-pass filter settings for OPL output:

sbtype Filter type Cutoff frequency
sb1
sb2		 1st order (6dB/oct) 12kHz
sbpro1
sbpro2		 1st order (6dB/oct) 8kHz
sb16 no filter N/A
opl_remove_dc_bias¶

Remove DC bias from the OPL output.

Possible values: on, off default

Some games play digitised music and sound effects using the OPL (AdLib) channels by rapidly changing the volume in very crude steps, similar to how the Disney Sound Source and Covox LPT DAC operate. This can produce annoying pops. Enable this setting to eliminate them.

Known affected games: Golden Eagle (1991), Wizardry VI: Bane of the Cosmic Forge (1990), Wizardry VII (1992).

Recommended settings for Wizardry VI when configured for AdLib sound:

[sblaster]
sbtype = none
oplmode = opl2
opl_remove_dc_bias = true
opl_filter = lpf 2 5500

[speaker]
pcspeaker = off

[autoexec]
mixer opl 500
oplmode¶

OPL mode to emulate.

DOSBox uses the highly accurate NukedOPL library to achieve a nearly bit-perfect emulation of the Yamaha OPL chips.

Possible values:

  • auto default – Use the appropriate model determined by sbtype.

  • opl2 – Yamaha OPL2 (YM3812, mono).

  • dualopl2 – Dual OPL2 (two OPL2 chips in stereo configuration).

  • opl3 – Yamaha OPL3 (YMF262, stereo).

  • opl3gold – OPL3 and the optional AdLib Gold Surround module. Use with sbtype = sb16 to emulate the AdLib Gold 1000.

  • esfm – ESS ESFM (enhanced Yamaha OPL3 compatible FM synth).

  • none/off – Disable OPL emulation.

Note

  • sbtype = none and oplmode = opl2 emulates the original AdLib card.

  • Only oplmode = esfm is not enough to get ESS Enhanced FM music in games; you’ll also need to set sbtype = ess. oplmode = esfm is useful to get ESFM-flavoured OPL with original Sound Blaster models.

CMS¶

cms¶

Enable CMS emulation.

Possible values:

  • auto default – Auto-enable CMS emulation for Sound Blaster 1 and Game Blaster.
  • on – Enable CMS emulation on Sound Blaster 1 and 2.
  • off – Disable CMS emulation (except when the Game Blaster is selected).
cms_filter¶

Filter for the Creative Music System (CMS) / Game Blaster output:

  • on default – Filter the CMS output. This applies a 1st order low-pass filter at 6 kHz (lpf 1 6000).
  • off – Don’t filter the CMS output.
  • <custom> – Custom filter definition; see Custom filter settings for details.