DOS Days

Retro Review: Creative Labs Sound Blaster Pro 2 - Part 1

23rd July 2023


A month ago I picked up several ISA sound cards, including a Multiwave AudioWave 16 AISP, an Orchid NuSound PnP 32, and this Creative Labs Sound Blaster Pro II, model CT1600. In this retro review, we'll take a deep dive into this Sound Blaster card.


Creative Labs Sound Blaster Pro II (CT1600)
Bought in June 2023 for £35 + P&P

The price I paid for this is frankly astonishing, and it's supposedly in good working order. In 2023, Creative Labs ISA-based cards (not the later ViBRA or Live! ones) seem to fetch silly money, often going for over £100. An original Sound Blaster 1.0, 1.5 or 2.0 will easily sell for over £150. This is probably due to a combination of the perceived rarity of the card and nostalgia, since Sound Blasters are what most PC owners bought back in the 90s so we want to re-experience the same sound. In the vast majority of cases there is no alignment between price and sound quality/compatibility - you can pick up a better-sounding/lower noise sound card for a lot less money that will have all the functionality and compatibility of a Sound Blaster. Anyway, whether you're a Creative Labs fan or not, my goal is to be objective in this retro review - I never had a Sound Blaster Pro back in the 90s, so I'm not in any way influenced by nostalgia here. Now onto a bit of history...

The Sound Blaster Pro was first released in November 1991, and bettered the original Sound Blaster by offering stereo output. It wasn't the first sound card to have this feature - that credit goes to MediaVision for their Pro Audio Spectrum, released six months before. In terms of compatibility with the sound standards at the time, the Sound Blaster Pro was fully backward-compatible with the original 8-bit Sound Blaster, and by translation, Ad Lib.

The CT1600 was Creative's second Sound Blaster Pro card after the original CT1330, with the key difference being that the two Yamaha YM3812 (OPL2) FM synthesizer chips on the original were replaced with a single Yamaha YMF262 (OPL3). In addition the UART circuitry used for MIDI was upgraded to one that supported full duplex.

The Sound Blaster Pro 2 also added a new analogue low-pass filter which is enabled by default, but can be switched off if you prefer to. This allows more of the lower frequencies to pass through into the audio output, resulting in it sounding more bassy. I've heard of reports that the audio from the CT1600 sounds more muffled compared to some other Sound Blaster cards, which I guess is a perception some might have if an audio track has more dominant lower frequencies compared to the rest of the frequency range. Many folks appreciated this addition, and since you can disable it, you have the option either way.

Generally-speaking, this card improved on its forebear with lower noise/interference and distortion.

Being of 1991 vintage, it's a non-Plug & Play card so it has jumpers to configure the base address, IRQ and DMA channel to use.

Sadly my card here is missing its faceplate so I will have to try and source one elsewhere.


Quick Visual Inspection

Let's explore what's on this busy-looking card:

  • Yamaha YMF262-M - FM synthesizer chip
  • Creative CT1336A - Bus Interface chip
  • Creative CT1341 - DSP chip
  • Creative CT1345S - Mixer chip
  • Yamaha YAC512-M - Digital-to-Analog Converter
  • ST Microelectronics TEA2025B - stereo audio amplifier
  • Creative 004713010 - CD-ROM controller
  • One crystal oscillator - 14.318 MHz
  • One black 40-pin header - CD-ROM interface
  • One white 4-pin header for CD Audio-in
  • Various jumper blocks and other headers
  • Faceplate with 15-pin game/MIDI port, volume thumbwheel, Speaker Out, Mic-in, and Line-in 3.5mm jack sockets

Date-wise, the most recent date stamp on the card's chips is week 48 of 1993, so the original manufacturing date of this Sound Blaster Pro II was certainly no earlier than the last week of November 1993. This puts it in the middle of the lifetime of the CT1600 - the Sound Blaster Pro 2 continued to be updated and sold alongside the Sound Blaster 16 for most of the SB16's life before Creative switched to the much more tightly-integrated ViBRA chip.

The Component Parts

The Yamaha YMF262-M

Known also as OPL3, the Yamaha YMF262 was already three years old when the Sound Blaster Pro arrived. It was one of the most popular and widely-used FM synthesizer chips used on sound cards during the DOS era, seeing use on cards from Aztech Labs, Ad Lib, ESS Technology, MediaVision, Oak Technology, Orchid, Terratec, Diamond Multimedia, Turtle Beach and many more.

YMF262 was Yamaha's successor to their also successful YM3812 which was known as OPL2 - the chip used in the original Ad Lib sound card. The YMF262 was essentially two YM3812's in a single chip, and thus supported 22 audio channels over the YM3812's eleven. Where the YM3812 produced monaural output, the YMF262 output in stereo (11 channels for left, and 11 for right).

The earlier Sound Blaster Pro 1, model CT1330, could also output in stereo and did so by using two YM3812 chips along with two DACs - one for each of the FM synth chips. The MediaVision ProAudio Spectrum had the same. With the YMF262, only one DAC was required.

As I mentioned earlier, having a single YMF262 made for some subtle differences in how you programmed the audio compared to having two YM3812 synth chips. Depending on the time of a game's release, some only worked in stereo on the original Sound Blaster Pro, as the code assumed and looked for two YM3812s. Later games would provide an option in the setup utility for Sound Blaster Pro (early or 1.0) and Sound Blaster Pro (later or 2.0), to cater for both cards. If a game has an explicit Sound Blaster Pro setup option but only outputs monaural digital sound (even when stereo is chosen), it is likely it was designed for the Sound Blaster Pro 1. Formula One Grand Prix, Hi-Octane, Dragonsphere, and Ultima Underworld are such cases. F-15 Strike Eagle III and almost every other SBP-supported game either has an option for both cards or works automatically with them both, though there are games that have a 'Pro' option but only utilise the mono Sound Blaster audio.


Creative CT1336A

The CT1336A is the Bus Interface chip - basically controlling the flow of instructions and data to and from the ISA bus. It was first used on Creative's Sound Blaster 2.0 (model CT1350) and integrated a number of other logic ICs and discrete components into a single ASIC, thus reducing the cost of manufacture.

I am aware of only two revisions of this Bus Interface chip - CT1336 and CT1336A. The original Sound Blaster Pro 1 as well as the earlier revisions of the Sound Blaster Pro 2 (up to 59234) used the CT1336, while all later revisions used the updated CT1336A. Other OEM versions of the SB Pro 2 were a bit more random in which one they came with.


Creative CT1341

The CT1341 is the DSP chip, or Digital Signal Processor. To be precise, Creative actually called this the "Digital Sound Processor" but in general audio parlance the aforementioned name is correct. This chip handles the 'digital audio' side of the Sound Blaster card for speech and sound effects (as opposed to the YMF262 which handles the 'music' side).

The first DSPs from Creative arrived with the first Sound Blaster 1.0 card. It allowed the card to play back mono sampled sound at up to 22 kHz sampling frequency (about the same as FM radio quality), and record at 12 kHz (about the same as AM radio quality). The CT1341 arrived with the introduction of the Sound Blaster Pro, which doubled these mono sampling frequencies to 44 kHz playback and 22 kHz recording, or 22 kHz/11 kHz in stereo. For gamers, the 44 kHz 16-bit audio playback capability is really not of any benefit since almost every game during the DOS era used 22 kHz 8-bit samples.

As you may be well aware, Creative Labs produced a number of DSP versions throughout the life of their ISA-based Sound Blasters, and are more widely known because many versions caused a 'hanging note' when MIDI output was used (or rather, when it was stopped). Fortunately, this bug didn't affect any of the original and Pro cards. On the Sound Blaster Pro 1 (CT1330), all cards came with DSP version 3.01. On Sound Blaster Pro 2 cards you either got DSP version 3.01 or 3.02.


Creative CT1345

The CT1345 is the mixer chip, responsible for combining the audio signals from the various inputs before they are sent to the audio amplifier and from there to the Speaker Out socket.

The CT1345 was the successor to the CT1335 found on the Sound Blaster 2.0, and was the first stereo mixer chip on a Creative card. It provided 8 levels of software volume control on both left and right channels for Master, Voice, MIDI, CD and Line-In sources, and 4 levels for the Microphone output source. The output mixing path took signals from the Voice, MIDI, CD, Microphone and PC speaker sources.

The earlier Sound Blaster Pro 1 came with the CT1345, as did the first two board revisions of the Sound Blaster Pro 2 (up to 49219). The upgraded CT1345-S can be found on all later board revisions (from 59234 up). Some later boards having rev.89414 came with the even later CT1345-T1.



TEA2025B Stereo Audio Amplifier

The onboard audio amplifier produces up to 4 Watts per channel from 4-Ohm speakers, or 2 Watts per channel from 8-Ohm speakers.

This same TEA2025B IC from ST Microelectronics can be found on many ISA sound cards including the Aztech Sound Galaxy BX/NX/NX Pro 16/Basic 16/Pro 16, Creative Music System (CMS), Sound Blaster 1.0/1.5/2.0, Sound Blaster Pro 1, Sound Blaster 16, AWE32, and various OPTi-based cards with 82C925/82C928/82C930/82C931 chipsets, to name but a few.

The IC above the amplifier is a TDA7284, which is more commonly found in audio cassette recorders, and handles the switching from recording to playback, and has Automatic Level Control (ALC) circuitry.


CD-ROM Header and Creative 004713010 chip

The 40-pin header on the left side of the card is a Panasonic CD-ROM interface, also called the "Panasonic MKE" interface for Matsushita-Kotobuki Electronics, or "SLCD" interface - gee, that's too many names for one thing...

Creative Labs teamed up with Panasonic when the multimedia boom began, so this interface is often called 'Creative/Panasonic' or 'Panasonic/Matsushita'. Only the Sound Blaster Pro 2 and some early Sound Blaster 16 cards used this interface.

It was an interesting time when the major CD-ROM manufacturers were all vying to be the #1 standard, so we had Creative/Panasonic, Mitsumi, Philips/LMSI and Sony in that battle - ironically it would be IDE/ATAPI that won out in the end as that standard solidified. Any optical drive that supports the Panasonic interface will work with this card, and you can use a standard 40-pin IDE ribbon cable to connect it to the drive.

Because the YMF262 did not have an integrated CD-ROM controller inside the chip, the Sound Blaster Pro cards have a separate controller IC on the card in the form of the Creative chip marked 004713010 that lives right next to the 40-pin header.

I believe the list of compatible CD-ROM drives for the Panasonic interface was really small:

  • Panasonic/Matsushita CR-521-B or CR-521-C - 1x speed (150 KB/sec) caddy-loading - uses CDMKE.SYS driver?
  • Panasonic/Matsushita CR-522-B or CR-522-C - 1x speed (150 KB/sec) caddy-loading - uses CDMKE.SYS driver?
  • Panasonic/Matsushita CR-523-B or CR-523-C - 1x speed (150 KB/sec) caddy-loading - uses CDMKE.SYS driver?
  • Panasonic/Matsushita E2550UA - 2x speed (300 KB/sec) tray-loading
  • Panasonic/Matsushita E2800UA - 2x speed (300 KB/sec) tray-loading
  • Panasonic/Matsushita Model CD 200 - 2x speed (300 KB/sec) tray-loading
  • Panasonic/Matsushita CR-562-B - 2x speed (300 KB/sec) tray-loading - uses CDMKE41.SYS driver
  • Panasonic/Matsushita CR-563-B - 2x speed (300 KB/sec) tray-loading - uses SBCD.SYS driver
  • TEAC CD-55A ? - 4x speed (600 KB/sec) tray-loading - not sure about a driver for this one
  • Sanyo CDR-H94A - 2x speed (300 KB/sec) tray-loading - uses GENCDDRV.SYS driver

The Sound Blaster Pro series of cards was the first from Creative to offer a variety of other CD-ROM interfaces, with cards like the CT2600 (also a Sound Blaster Pro 2) coming with a Mitsumi interface instead.


Headers and Jumpers

As I mentioned, this card is *not* ISA Plug & Play, so you must set jumpers on the card to define the I/O base address, interrupt request line and DMA channel that the card will use.

Depending on the board revision, the location of the jumpers are slightly different, but they are typically located in the same approximate area of the board.

  • I/O Base Address - Can be set to 220h or 240h - JP13 and JP14
  • IRQ - Can be set to 2, 5, 7 or 10 - JP18-JP21
  • DMA Channel (low) - used by the FM synth, can be set to 0, 1 or 3 - JP5-JP7
  • DMA Channel (high) - used by the digital audio part, can be set to 0, 1 or 3 - JP15-JP17
  • Joystick enable/disable - this does not affect the use of MIDI on the port, which is always enabled - JP4
  • DMA Sharing / DMACTL - allows the card to share a DMA channel with another card (default is disabled) - JP11

The factory defaults for the Sound Blaster Pro are I/O base address at 220h, IRQ 5 (SB and early SBP cards were IRQ 7), and DMA channel 0 for both the FM (DRQ) portion of the card and the digital audio (DACK) portion. According to the Getting Started guide, both DRQ and DACK must be configured to use the same DMA channel. This is a little strange, as other 16-bit stereo sound cards allow the use of the higher DMA channels for the digital audio portion with the FM part using the traditional 0, 1 or 3 channel. The early revision Sound Blaster Pro cards were configured from the factory to use IRQ 7, just like the original Sound Blaster. At some point around board revision 3 or 4, this was changed to be IRQ 5. IRQ 7 is often used by a parallel port in a PC, so this may be why they changed it to avoid potential resource conflicts.

On most board revisions there is also an 8-pin Audio Extension Connector at JP2 (right behind the Mic-In and Line-In sockets). This can be used to connect other audio or video cards to your Sound Blaster Pro, and mix in this external audio with the other audio lines on the card, e.g. Mic-In, Line-In, etc. I'm not 100% sure what JP3 does - the Getting Started guide isn't much help though it appears to define whether the right channel is to be use purely as the second stereo [right] channel or as the speaker return signal (?!) - if you have any ideas, let me know!


Joystick/MIDI Port

As with all(?) Creative Labs sound cards, the 15-pin MIDI port is *not* Roland MPU-401-compatible. According to the user manual, "Sound Blaster Pro's MIDI port complies with the International MIDI Association recommended standard. The MPU 401 has some intelligence in its MIDI implementation. This intelligence could be easily emulated by a small driver routine in the PC. Hence, programs that run on the MPU 401 cannot work directly on the Sound Blaster Pro.".

So in other words, the MIDI implementation on this card, as well as all earlier Sound Blasters and many later ones, does not have any of the Roland MPU-401 Intelligent mode circuitry/firmware (which was designed to take a lot of the processing effort off the main PC's CPU), nor does it communicate in the same way as other sound cards that support Roland MPU-401 in UART mode (just about every other manufacturer's sound card out there) - it uses the onboard DSP in what is often now called SB-MIDI. This was very poorly supported by games with maybe just a few that did (Flashback is an example of one game that directly supported SB-MIDI). SoftMPU does support emulating an MPU-401 with a Sound Blaster card that only supports SB-MIDI - just use the /OUTPUT:SBMIDI flag.

To use the MIDI port for connection to MIDI devices or keyboards, you also needed to have the MIDI Kit. This comprised a MIDI adapter with a joystick port to allow you to connect both a joystick and a MIDI device at the same time as well as some sequencing software to allow you to record, playback and edit MIDI files. The MIDI Kit wasn't bundled in either the standalone retail sound card packaging, nor in any of the Multimedia Kits that featured the Sound Blaster Pro.

As I mentioned further up, you can disable the joystick part of this port via jumper JP4 (say, if you already have a joystick port in your PC). Disabling the joystick does not prevent you from using this 15-pin connector for MIDI purposes.

Since my card doesn't have the backplate it's a good thing the silkscreen has a name for each of the jacks. From the top (if the card is installed in a vertical slot), they are:

  • Line-In
  • Mic-In
  • Volume thumbwheel
  • Speaker-Out

Sadly this card doesn't have a line-out, so there is no way of circumventing the onboard amplifier for the cleanest audio output.

Sound Blaster Pro Compatibles

As I previously mentioned, the Sound Blaster Pro's stereo output wasn't ground-breaking - MediaVision's Pro Audio Spectrum card pioneered this six months before the SBP's first release. After the Sound Blaster Pro's arrival, however, most of the other sound card manufacturers jumped into action to ensure their latest cards/audio chipsets were Sound Blaster Pro-compatible, meaning they too would support the all-important stereo feature.

The table below outlines most of the competitors that have Sound Blaster Pro-compatibility. It does not include cards that also support Sound Blaster 16-compatibility, since this is considered a generation beyond what we're reviewing here:

Ad Lib Gold (1991)
Aztech Sound Galaxy NX Pro Extra (1993)
Aztech Sound Galaxy NX Pro 16 (1993)
Aztech Sound Galaxy NX Pro 16 Extra (1993)
Aztech Sound Galaxy Basic 16 (1994)
Aztech Sound Galaxy Pro 16 (1994)
Aztech Sound Galaxy Basic Audio 16 (1994)
Aztech Sound Galaxy Nova 16 (1994)
Aztech Sound Galaxy Nova 16 Extra (1994)
Diamond Multimedia Sonic Sound (1993)
Ensoniq SoundScape VIVO (1995)
Gravis UltraSound VIP / ViperMAX / Extreme (1995)
Guillemot MaxiSound 64 Home Studio SC8500 (1994)

(all cards with Analog Devices AD1848)
(all cards with Crystal CS9233)
(all cards with ESS AudioDrive ES688)
(all cards with ESS AudioDrive ES1488)
(all cards with ESS AudioDrive ES1688)
(all cards with ESS AudioDrive ES1698)
(all cards with ESS AudioDrive ES1788)
(all cards with ESS AudioDrive ES1868)
MediaTrix AudioTrix Pro (1994)
MediaVision ProAudio Spectrum (1991)
MediaVision Jazz16 (1993)
MediaVision ProSonic 16 SCSI (1994)
MediaVision Pro 3D / Premium 3D (1994)
miro miroSound PCM 1 Pro (1994)
miro miroSound FM 10 (1995)
miro miroSound PCM 10 / PCM 12 (1995)
Multiwave AudioWave Green 16 (1994)
Multiwave AudioWave Platinum 16 (1994)
Multiwave AudioWave 16PNP (1995)
Multiwave AudioWave 32PNP (1995)
Oak Technology Mozart-16 (1994)
Orchid SoundWave 32 / 32 Pro (1993)
Orchid NuSound PnP 32 (1995)
Turtle Beach Tropez (1994)
Yamaha Audician 32 Plus (1996)

(all cards with OPTi 82C924)
(all cards with OPTi 82C925)
(all cards with OPTi MAD16 / 82C928 / 82C930A)
(all cards with OPTi MAD16 Pro / 82C929A)


Part 1 Summary

So there we are with Part 1. I said I'd mention the differences between the board revisions, so here it is:

There were six revisions of the CT1600 board, as follows:

  • 39151 - Week 51 of 1991 (rare) - DSP v3.01, CT1336, CT1345.
  • 49219 - Week 19 of 1992 (common) - DSP v3.01 or DSP v3.02, CT1336, CT1345.
  • 59234 - Week 34 of 1992 (rare) - DSP v3.02, CT1336, CT1345. 14.317 MHz crystal oscillator added to ensure stable clock for YMF262 chip instead of relying on ISA bus clock, DRQ jumpers moved to right of the crystal.
  • 69237 - Week 37 of 1992 (common) - DSP v3.02, CT1336A replaced the CT1336 from earlier revisions, some have CT1345 while others have the later CT1345-S. LS122 in upper left corner changed to be in larger DIP package.
  • 79337 - Week 37 of 1993 (rare) - DSP v3.02, CT1336A, CT1345-S. Major PCB revisions made: Audio Extension connector omitted, DAC moved much closer to YMF chip (to reduce noise?), voltage regulator now oriented vertically, grounding plane under small crystal next to CD-ROM interface header made larger, 7404 logic chip below YMF262 at U56 replaced with transistor.
  • 89414 - Week 14 of 1994 (fairly rare) - DSP v3.02, CT1336A, CT1345-S or the later CT1345-T1. Copyright label on silkscreen moved to right, above ISA slot connector.

My one here is the 69237 variant, and has the later '-S' mixer chip. The rarity I mention above are just my own personal observations - ultimately a CT1600 is a CT1600 regardless of board revision - the value of one compared to another is negligible, as you'd be hard pressed to hear any audible difference between them, though the amount of noise I'm sure will differ, especially between revisions 3 to 6 compared to revisions 7 and 8. The major PCB changes made from revision 7 onwards were almost certainly to reduce noise, and some anecdotal searching around the internet seems to confirm that these later revs are much quieter than rev 6 and earlier.

I also read that these cards may not play nicely on machines that are too fast/beyond their time - a problem that certainly plagues anyone today trying to use any original Sound Blaster or even a Sound Blaster Pro 1, but that was apparently a weakness of the Yamaha YM3812, so it will be interesting to find out if the YMF262 behaves better on faster machines. I have numerous YMF262-based cards and have never had issues running them on a Super Socket 7 PC with caches enabled. Anyway, something I should bear in mind when testing!

Also on the topic of testing, I will record and compare the audio output with the low-pass filter enabled and disabled, and give you my impressions of each.

Head to Part 2 where I will install the original DOS drivers and test out its audio capabilities, including comparisons to other cards from the same era.