Monday, July 23, 2012

Sound Blaster 16 - Distinguishing the Endless Models

No vintage PC product line is more complex than the Sound Blaster 16.  These cards were extremely common from 1992 to the end of the DOS era (1997).  Their basic advance over the Sound Blaster Pro, 16-bit sound, is still the basic standard today.  But the cards went through many generations and many OEM models.  For the system builder, it is extremely difficult to find the right one without doing the homework.  As there are an enormous number and variety of SB16s, I will not try to identify the features of every model.  Here are some considerations :

Waveblaster Header

Value and OEM cards generally do not have it, although there may be solder points for it.  However, the passive components on the motherboard that assist in implementing the interface may be missing.  Waveblaster MIDI daughterboards will suffer from the hanging notes bug, as will MIDI modules connected through the gameport.

Hanging MIDI Notes Bug

It is important to identify games which produce hanging  notes as a result of incompatibility with the various DSP versions of the 16-bit Sound Blaster series. : DOOM, DOOM II, Heretic, Hexen, Raptor, Hocus Pocus, Duke Nukem 3D and Blood are all examples of games which suffer from this bug.  There are other games which may occasionally produce hanging notes regardless of the midi interface being used.  Any game using LucasArts iMuse system may be subject to it.  This includes Star Wars - X-Wing and Tie Fighter (floppy versions) are good examples of such a game.  Only the former are addressed here.

The affected DSPs have been identified as versions 4.11, 4.12 & 4.13.  DSP versions 4.04, 4.05 and 4.16 will not suffer from this bug.  The bug will only occur when digital sounds and midi are being played.  The best fix for the problem is to use another card for MIDI.  This bug will not be present in any card using the CT-1747 chip.

ISA Plug N Play

First generation SB16s with the CT1746 Bus Interface chip were strictly configured by jumpers.  No software initialization required.

Second generation SB16s with the CT1747 Bus Interface and OPL chip required jumpers to set the I/O range (IOS0 & IOS1), joystick enable/disable (JYEN) and MIDI I/O Select 330/300 (MSEL).  However, IRQ and DMA selection were done in software on startup.  SBCONFIG.EXE or DIAGNOSE.EXE needed to be loaded in AUTOEXEC.BAT to tell the card which resources to use at boot.

If you have a ViBRA chip, then you may have an ISA Plug N Play card.  They are initialized through the software Creative Technology Configuration Manager (CTCM.EXE) and configured and disabled through the Creative Technology Configuration Utility (CTCU.EXE) or in PNP operating system like Windows 95.  This allows you to disable the joystick, the MPU-401 MIDI interface, the Adlib Ports, High DMA or the whole card.  Unfortunately, if you have to load CTCM, it adds noticeably to the boot time when booting to DOS.

SB16s with the ViBRA chips are be detailed below.  

CD Interfaces

First generation SB16s supported Panasonic, Mitsumi or Sony CD Interfaces.  One board, the Sound Blaster 16 SCSI, had a SCSI port for a SCSI CD-ROM, and it could not be disabled.  The SCSI interface took up an IRQ and did not support booting hard drives.  The next generation began to add IDE support.  On retail boards, the IDE port should be able to be disabled.  On some OEM boards, the CD Interface ports may not able to be disabled by design.  The Panasonic interface is harmless because it does not require any resources beyond the I/O range used by the Sound Blaster 16.

QSound Advanced Signal Processor/Creative Signal Processor

Many boards have a CT-1748 ASP/CSP chip or a socket for one.  The ASP/CSP was generally upgrade option, which never really caught on and omitted on the cheaper boards.  Except for the CT-2502 boards, you will never see the chip or the socket for one on a ViBRA board.  TFX is the only game known to support the chip.

True Yamaha OPL3 Synthesis

You will get true Yamaha OPL3 synthesis if your board has a Yamaha YMF-262 or YMF-289 chip or CT-1747 chip.  The CT-1747 contains an OPL3 core licensed from Yamaha.  If you have a CT-1978 chip or the ViBRA CT-2505 or CT-2511 chips on the board, you will get Creative CQM synthesis.

ViBRA Chips

The ViBRA series of chips sought to achieve a higher degree of integration among the various component chips that made up the original Sound Blaster 16.

CT2501 ViBRA 16
Integrates the Bus Controller Interface, the DSP, the Mixer and the Codec.  

Jumper configured
No treble, bass or gain controls in integrated analog mixer
80db SnR

I have never seen this chip branded with the ViBRA logo, and it is not a home-grown Creative Labs chip, as it contains technology licensed from Crystal Semiconductor.  I think this is also known as the ViBRA Pro.

Treble, bass and gain controls in integrated analog mixer
85db SnR (best SnR on any Creative Labs ISA sound card, even the AWE64 Gold)
CT-1978 or YMF-289 (less common, but makes for an awesome board)

CT2504 ViBRA 16S
Tends to be found on SB16s integrated on the motherboard.

IRQ/DMA software setting
YMF-262 or CT-1978
80 SnR
No treble or bass controls

CT2505 VIBRA 16C
Tends to be found on SB16s integrated on the motherboard.

See above, except :
Integrated CT-1978
DSP v4.16

Was used on the last, cheapest SB16s, especially those branded with the WavEffects logo.

See above, except :
High DMA channels not supported, uses two low DMA channels for 16-bit sound.

Of the ViBRA's, the two potential compatibility issues are the loss of the mixer settings in all but the CT2502 and the DMA channels in the VX.  I doubt that games used those settings anyway.  As the mixer receives analog signals, this can be replicated to some extent using an external mixer.  

As far as the DMA channels in the VX, this will not be an issue unless you select a Sound Blaster 16 in the install of a DOS game and the game requires a High DMA channel.  Windows and its games will be fine so long as the proper drivers are installed.  

Which One to Buy

The least hassle of the SB16s are the CT1740 and CT1750, which along with the CT1770 were the first retail Sound Blaster 16s.  With a 4.05 or lower DSP they will not have the hanging notes midi bug, will output genuine FM, require no software initialization and will not take up extra resources.  However, they have the nickname "Noise Blaster" and it is deserved.  Everything will sound noisy on the card, moreso than its predecessor the Sound Blaster Pro 2.0.  The Waveblaster output is affected and I found the sound from a SCB-55 to be comparatively muffled compared to the same daughterboard on a MPU-401AT.  If you can live with the potential hanging notes midi bug, look for the CT2750, which is silkscreened the Sound Blaster 16 EASY, and it has no CD interfaces on it.

If you want the freedom to choose your IRQs and DMAs in software, you could try the CT2230 with jumpers to disable the proprietary CD interfaces or the CT2770 which only has the Panasonic interface.  Be wary of SB16s with an IDE port, as the port may not be able to be disabled.  Some cards of the same model number have the ports while others only have silkscreening for the header and glue logic.

If you want the least noisiest cards of the bunch, look for the CT2940 with a Yamaha YMF chip. This card has the CT2502 (ViBRA) chip but uses ISA PNP.

If you look at other ViBRA cards, you could try the CT2800 or CT2900 which have Yamaha chips, software selectable IRQ and DMAs and a disable IDE jumper setting.

Three Generations of Sound Blaster 16s Compared

Number One : Sound Blaster 16 MCD CT-1750

CODEC : CT1701
FM Synthesis : Discrete Yamaha YMF-262 OPL3
DSP : Discrete 4.01-4.12
Mixer : Discrete CT1745
CD-ROM Drive Interfaces : Panasonic, Sony, Mitsumi
Configuration : Jumpers
ASP/CSP : Socket or Soldered
Waveblaster Header : Present
Amplifier : Jumpers & Volume Wheel
PCB Headers : Creative CD-ROM, PC Speaker In

This is a first generation Sound Blaster 16.  Its main weakness is that most 8-bit digitized sound has an audible layer of hiss surrounding the sample playback.  This hiss is not observed when playing back FM music.  Mixing the audio from the Waveblaster connector sounds muffled.  When 8-bit digital samples play there are often pops and clicks in the audio output.  Everything is configured by jumpers, and its best to set the Panasonic interface to be the active interface because it does not consume any more resources beyond the Sound Blaster itself.

Number Two : Sound Blaster 16 MCD CT-2230

CODEC : CT1703 or CT1701
FM Synthesis : Integrated Creative/Yamaha CT-1747 OPL3
DSP : Discrete 4.11-4.13
Mixer : Discrete CT1745
CD-ROM Drive Interfaces : Panasonic, Sony, Mitsumi
Configuration : DIAGNOSE.EXE or SBCONFIG.EXE + Jumpers
ASP/CSP : Socket or Solder Pads
Waveblaster Header : Present
Amplifier : Separate Jacks
PCB Headers : Creative CD-ROM, MPC-2 CD-ROM, PC Speaker In

This is a second generation Sound Blaster 16.  The noise, pops and clicks associated with the first generation are fully gone when paired with the later CODEC.  The IRQ and DMA selection is done by software settings on startup.  The settings requiring jumpers are the I/O address selection, the MPU-401 MIDI interface enable and address selection and the joystick enable.  My card has no headers for any interface other than the Panasonic interface.

Number Three : Sound Blaster 16 PnP CT-2940

CODEC : CT1703
FM Synthesis : Discrete Creative CT-1978 CQM or Discrete Yamaha YMF-289 OPL3-L
DSP : Integrated 4.13
Mixer : Integrated CT1745
CD-ROM Drive Interfaces : IDE
Configuration : CTCM.EXE + CTCU.EXE
ASP/CSP : None
Waveblaster Header : Present
Amplifier : Separate Jacks
PCB Headers : Creative CD-ROM, MPC-2 CD-ROM, PC Speaker In, AUX 1, AUX 2, TAD, MBPro

This is a third generation Sound Blaster 16.  Most of these cards typically come the Creative CQM chip, but this card comes with a Yamaha OPL3 chip.  This card is totally jumper free and adheres to the ISA PnP standard.  It can be configured with Creative's utilities or with PnP-supporting operating system like Windows 95.  Reportedly, the integrated mixer has the highest signal to noise ratio of any ISA Sound Blaster, even the Sound Blaster AWE64 Gold.  My card has no header or circuitry for the ISA interface, so it does not take up any resources.  Its only other downside beyond the PnP is that its MIDI interface does have the hanging notes bug.


  1. I found the Vibra Pro CT2940 does not require CTCM, but works fine with "diagnose /s". In fact, currently it works fine in DOS without any initializer, except the BIOS PnP manager and "set blaster=..".
    Regards, Gerwin.

  2. thank you for this post! nice work!

  3. What about CT2290? it isn't mentioned here at all.

  4. Hello. In the section you are talking about true Yamaha OPL synthesis, you write:

    "If you want the least noisiest cards of the bunch, look for the CT2940 or CT2980 with a Yamaha YMF chip. These have the CT2502 (ViBRA) chips and are ISA PNP."

    Are you sure, you don't mean the CT2890 and not the CT2980?