Creative Labs propelled the home PC industry into a future where sound is seriously considered. In this article, I'll be sharing some of the history behind the Sound Blaster, why it was important, and pitfalls to remember when purchasing old models today.

Note: This will be a constantly updated post as new information becomes available.

Ad Lib

In the late 80s, IBM PCs (and their compatible clones) didn't make a whole lot of sound beyond the little internal PC speaker. In 1987, a Canadian company called Ad Lib, Inc. released a sound card named after the company itself. (Or perhaps, the company was named after their product. Will we ever know?)

The AdLib card contained an FM synthesis chip for producing rich timbres. The chip is the OPL2, designed by Yamaha. When people talk about how DOS game music sounded, they're almost always talking about this chip if it's not a digital soundtrack. There isn't much more to the AdLib, and it could even be built from off-the-shelf parts.

In 1989, Creative Labs released the very first Sound Blaster card. It was 100% compatible with the AdLib, and added "DSP" functionality which allowed programs to output digitized sound effects and music. The card became an immediate success and paved the way for Creative's dominance within the home PC sound card market. Ad Lib, Inc. could not keep up with their own offerings and, in 1992, despite being the inspiration for the whole thing, went bankrupt.

Features

• Original Sound Blaster models (1.0, 1.5, 2.0)
  • Mono output
  • OPL2 FM synthesis
  • Digital sound playback
• Sound Blaster Pro models (Pro 1.0, Pro 2.0)
  • Stereo output
  • Fully backwards compatible with Sound Blaster 2.0
  • Dual OPL2 (Pro 1.0) or OPL3 (Pro 2.0)
  • Digital sound playback
• Sound Blaster 16 models (SB16, Vibra)
  • Stereo output
  • Fully backwards compatible with Sound Blaster 2.0 (not the Pro)
  • OPL3 or proprietary CQM FM synthesis
  • 16-bit digital sound playback
  • Wave Blaster capability
  • MPU-401 compatibility
• Sound Blaster 32 models (SB32, AWE32)
  • Fully backwards compatible with Sound Blaster 16
  • Onboard wavetable processing and ROM
  • Onboard RAM (AWE32 only)
• Sound Blaster AWE64
  • Fully backwards compatible with Sound Blaster 32
  • Greater polyphony than the Sound Blaster 32 models
  • Much improved SNR

Bugs

Creative's cards were known for being buggy in certain circumstances.

MPU-401 Hanging Notes

There is abundant information about the hanging note bug, which causes MIDI playback trouble for Sound Blaster 16 and (AWE)32 cards. Vogons user James-F claims the hanging notes apply to all MPU-401 interfaces. When this bug occurs, notes will occasionally continue to play after they were supposed to have stopped playing.

MPU-401 High Pitched Ringing

Under these conditions, high pitched ringing will play randomly:

• DSP version must be 4.11, 4.12, or 4.13
  • Cards older than the Sound Blaster 16 have DSP numbers less than 4 and are unaffected
• Digital sound must be playing
• Either a Waveblaster daughterboard or external MPU-401 interface must be in use
• The card does not use the CT1747 chip

The high pitched ringing is bad enough that affected cards should have their Waveblaster capability considered useless.

MPU-401 Stuttering

Music playback will stutter if the MPU-401 interface is used while digital audio at greater than 11khz is being played in some circumstances. Build engine games are especially succeptible.

Clicks and Pops During Digital Audio

A particular method of digital audio playback called "Single-cycle DMA Mode" causes clicks and pops on all Sound Blaster 16 cards that do not have a Vibra chip onboard. It isn't particularly noticeable when there's a lot of sound going on, but it is still audible.

Ringing or Hissing After Digital Audio

On cards utilizing the Vibra chip, a faint ringing or hissing may be heard after digital audio stops playing.

Not Actually Bugs

Occasionally, there will be differences among the cards and the way they were programmed that were, for a long time, misunderstood.

Reverse Stereo

Recent research on the Vogons forums led by user James-F has proven that the widespread "reverse stereo bug" is actually poor implementation by many software developers. That's not a hardware bug in the Sound Blaster, but some clone cards (including cards with Aztech and Yamaha chipsets) try incorrectly to compensate by swapping the left and right digital audio channels to make up for how the software was written.

Filter Cutoff on Digital Audio

Sound Blaster cards before the Sound Blaster 16 have a fixed low-pass filter to reduce the effects of aliasing, which sounds like metallic overtones when playing samples at a low sampling rate.

The Sound Blaster 16 has a dynamic filter which adjusts its cutoff frequency. This means samples playing at a lower sample rate will have a lower filter. This also means lower sample rate audio will sound more muffled than it did on earlier Sound Blasters. Whether this sounds better or worse is a hot debate topic, and seems to be entirely subjective.

Creative's "CQM" OPL Clone

At some point during the transition from manufacturing Sound Blaster 16 and AWE32 cards, it was decided within Creative to clone the Yamaha OPL3 chip they'd been using for FM synthesis called Creative Quadratic Modulation. I suspect it was a cheaper alternative to repeatedly licensing Yamaha's design.

Cards that are third generation (Sound Blaster 16) or newer that contain the CT1978 chip have CQM. If it's as new as a Sound Blaster AWE64 and still supports FM synthesis, then it contains the CQM regardless.

A demonstration of the difference in sound exists on Wikipedia.

Master List

This list is a work in progress. More data to come later.

Multiple Cards Sharing CT Numbers

There can be multiple variants of the same CT board, which may have different capabilities. In these cases, the base chipset is mostly identical. The CT2230 is one such example: note the differences in whether CSP is socketed or soldered, and which CD interfaces are present. When buying, be wary and always verify with photos.

Since the Sound Blaster 2.0, additional identifying codes were added to Sound Blaster cards. A six digit code on the lower-left corner of the card will identify which revision of the card it is. These cannot be used to uniquely identify cards, however. The CT1750 and CT1770 both share one such code.

It seems the first two digits are the revision number (starting at 01), the next two digits are the year, and the final two digits are the week number (1-52). This date supposedly indicates when the PCB was designed.

Notable Models

Some cards are either of note or have some unique things to know about.

CT1730 or CT1740?

I could not locate any cards that have CT1730 printed on the board itself. However, some CT1740 boards have CT1730 printed on their model sticker. It's unclear whether to assume that these two models are identical. It is suggested that the CT1730 is really the CT1740 with a low version DSP. Revision 049251 is known to have the CT1730 sticker and v4.05 DSP. Vogons user Boxpressed claims revision 059334 is also this way.

CT2770: Inconsistent Revisions

This card is a curiosity: revisions 01 and 03 use what appears to be the same PCB, but revision 02 looks completely different. Additionally, revision 01 has a later code date than revision 03. This is one specific model that goes against many of the "rules" of numbering. Despite all this, all revisions use the exact same chipset.

CT2940: Presence of OPL3

Even among cards of the same revision, some of them have the CT1978 CQM and some of them have a legitimate YMF289B-S OPL3. Be on the lookout whenever you come across these cards. The ones with the true OPL3 chip seem to be quite a bit more rare.

CT3670: The Covert AWE64 Value

The CT3670 is unique among the Sound Blaster 32 line of cards because it is effectively an AWE64 Value, but with SIMM slots and without onboard RAM. A SIMM is far easier to obtain than one of Creative's proprietary memory modules. The CT3670 chipset is identical to the AWE64 cards with model numbers CT4380 and CT4500.

CT4130 or CT4131?

Like the CT1730/CT1740 discrepancy above, the model number on the sticker may not match the model number printed on the board.

DACs

DACs convert digital audio signals to analog audio signals, suitable for output. Later DACs tend to improve fidelity and reduce noise in the signal. Vogons user James-F reports on quality for all DACs.

In order of highest quality to lowest quality:

• CT1703-A
• CT1703-TBS
• CT1703-T
• CT1701

Synths

Synths include all processors involved in generating both sound and music. It's safe to assume all synths are entirely Creative's own, except the following:

• CT1747 (Creative DSP with licensed Yamaha OPL3)
• SAA1099 (Philips SAA)
• YM3812 (Yamaha OPL2)
• YM262-M, YMF-278, YMF-289 (Yamaha OPL3)

Functionality

• DSP units
  • CT1321, CT1351: version 2.xx
  • CT1341: version 3.xx
  • CT1741, CT1743: version 4.xx
• PCM units
  • CT1321: SB 1.0 (integrated DSP)
  • CT1336: SB 2.0 & SB Pro
  • CT1345: SB Pro 2.0
  • CT1745: SB 16
• CT1705: Plug'n'Play controller
• CT1748: Fully programmable ASP/CSP chip

Features

• CSP: Socket for CT1748 (may or may not be installed)
• Goldfinch: Goldfinch (CT1920) add-on header
• IDE: 40-pin IDE header
• Joy: 15-pin joystick connector
• LMSI: LMSI connector
• Mitsumi: Mitsumi CD-Rom connector
• Panasonic: Panasonic CD-Rom connector
• PCSPK: 2-pin PC Speaker header
• RAM: onboard RAM
• RCA: white/red RCA audio output
• SBRAM: AWE64 proprietary RAM expansion slots
• SCSI: SCSI connector
• SIMM: standard SIMM RAM expansion slots
• Sony: Sony CD-Rom connector
• Vol: volume control via wheel
• WB: WaveBlaster header
• WT: onboard wavetable

Buying Guide

With so many different models out there, it can get overwhelming to find out which card is right for you.

Tips

• Every one of these cards after the Sound Blaster 2.0 is compatible with all Sound Blaster 2.0 features.
• The Sound Blaster Pro and Pro 2 have some specific features and programming that are specific to that line of products. Some older DOS games that have stereo sounds and Sound Blaster Pro support will be unable to use these stereo features on the Sound Blaster 16 and later cards.
• All cards before the Sound Blaster 16 will have issues on very fast machines. Anything faster than a Pentium II will necessitate one of these at a minimum.
• The 16, 32 and 64 lines are all identical as far as DOS games are aware. Some games such as Duke Nukem 3D can specifically support the AWE32 for MIDI music playback, but for the most part, a 16 is going to be capable of doing pretty much everything.

Legitimate OPL3 Cheat Sheet

If you care about having a useful Waveblaster header, genuine OPL3 and the highest quality DAC, look at these top-tier models:

• Without PnP
  • CT2230 (revision 4 has the CT1703-A)
  • CT2290
  • CT3900
• With PnP
  • CT2920
  • CT3960
  • CT3980

If you care less about the DAC, you could add any model with a DSP that is version 4.05 or lower (these tend to have the noisier DACs), plus these to your shopping list:

• Without PnP
  • CT2740
  • CT2760
  • CT2772

If you don't need Waveblaster support (since many of these others will cause high pitched squealy notes if you try to use external MIDI) and legitimate OPL3 is all you care about, look at these models in addition to the ones above. Many of the later ones use Vibra chips for digital audio:

• Without PnP
  • CT1740
  • CT1750
  • CT1770
  • CT1779
  • CT1780
  • CT2260
  • CT2700
  • CT2800
  • CT2810
  • CT2860
  • CT3930
• With PnP
  • CT2890

Other Information

On the Nerdly Pleasures blog, there are a couple great buying guides depending on which generation you seek. Here are the pertinent links:

• Vintage Gamer's Guide to Sound Blasters
• Sound Blaster 16 - Distinguishing the Endless Models
• Sound Blaster AWE32 & 64 Options

Conclusion

If you're looking for the ultimate in digital audio compatibility, look no further. Even on my most modern machines, I had no issue getting these cards to work. ISA Sound Blaster cards will be a bit more expensive than their clone counterparts, however.

It's a huge shame about the practically-unusable Waveblaster header on many of the Sound Blaster 16 and (AWE)32 models with a discrete OPL3. But if you don't plan to use a Waveblaster header, these should be your first choice.