veovis
Member
Greetings,
I have been interested in the Creative CMS or Game Blaster cards for quite some time but since the cards are fairly rare I haven't been able to obtain one. I stumbled across the work by Tronix described here and saw that he had some success at building a clone of the CMS card.
Tronix had problems with a large amount of noise making it into the output of his card but this was likely due to the lack of a good ground plane and separation of the audio from the digital signals.
Since I haven't been able to find an actual CMS card I decided to build my own based on the work by Tronix and the Sergey's auto detection circuit. In the end, I modified Sergey's auto detection circuit because it allowed the card to respond to addresses that it really shouldn't respond to. While I was at it, I added a jumper to set the card's IO address anywhere from 210 through 260 like the original creative card.
I decided to use the same TEA2025 amplifier that Creative used on the Game Blaster cards. Based on the pictures of the card that I was able to find, it looks like the amplifier on Creative's card is very similar to the reference example in the TEA2025 datasheet so I used the capacitor values from the datasheet.
The result is what I hope is an accurate sounding clone that should have nearly 100% compatibility with the CMS / Game Blaster. Due to the problems that Tronix experienced, I decided to go straight to a 2 layer PCB design and tried to keep the analog signals as far as possible from the digital lines.
I got my prototype PCBs back from the fab last week and built one of them this weekend. The card is detected by the Creative testcard utility and the audio output appears to be quite good. There is a little bit of background noise in the output when the card is not playing but it is not objectionable. In fact the noise level is about the same as the background noise level of the Sound Blaster 16 that I have in the same system.
One problem I encountered was I didn't have a 10k dual audio taper pot that was short enough to fit through the bracket once the card is installed in an ISA slot. So, I soldered 4 resistors in it's place to create a fixed output that is somewhere around line level. It looks a bit odd because the PCB footprint is for a pot but it works!
I think I may actually leave it that way because that way I can run the output of my clone card into the line in of another audio card to have both CMS and Sound Blaster support in the same system coming out the same set of speakers. I currently have my card set to address 220 and a SB 16 set to address 240 which appears to work fairly well.
I don't have a real CMS or Game Blaster card to compare to so I don't know how accurate the sound output is but it sounds pretty good to me.
Here are some quick recordings I made:
Compatibility appears to be very good. So far the card has worked in everything I have tried including Bubble Bobble which I understand doesn't normally work when using a Sound Blaster with the CMS chips.
The board layout and Eagle project files for my prototype is available here if anyone is interested.
I have been interested in the Creative CMS or Game Blaster cards for quite some time but since the cards are fairly rare I haven't been able to obtain one. I stumbled across the work by Tronix described here and saw that he had some success at building a clone of the CMS card.
Tronix had problems with a large amount of noise making it into the output of his card but this was likely due to the lack of a good ground plane and separation of the audio from the digital signals.
Since I haven't been able to find an actual CMS card I decided to build my own based on the work by Tronix and the Sergey's auto detection circuit. In the end, I modified Sergey's auto detection circuit because it allowed the card to respond to addresses that it really shouldn't respond to. While I was at it, I added a jumper to set the card's IO address anywhere from 210 through 260 like the original creative card.
I decided to use the same TEA2025 amplifier that Creative used on the Game Blaster cards. Based on the pictures of the card that I was able to find, it looks like the amplifier on Creative's card is very similar to the reference example in the TEA2025 datasheet so I used the capacitor values from the datasheet.
The result is what I hope is an accurate sounding clone that should have nearly 100% compatibility with the CMS / Game Blaster. Due to the problems that Tronix experienced, I decided to go straight to a 2 layer PCB design and tried to keep the analog signals as far as possible from the digital lines.
I got my prototype PCBs back from the fab last week and built one of them this weekend. The card is detected by the Creative testcard utility and the audio output appears to be quite good. There is a little bit of background noise in the output when the card is not playing but it is not objectionable. In fact the noise level is about the same as the background noise level of the Sound Blaster 16 that I have in the same system.
One problem I encountered was I didn't have a 10k dual audio taper pot that was short enough to fit through the bracket once the card is installed in an ISA slot. So, I soldered 4 resistors in it's place to create a fixed output that is somewhere around line level. It looks a bit odd because the PCB footprint is for a pot but it works!
I think I may actually leave it that way because that way I can run the output of my clone card into the line in of another audio card to have both CMS and Sound Blaster support in the same system coming out the same set of speakers. I currently have my card set to address 220 and a SB 16 set to address 240 which appears to work fairly well.
I don't have a real CMS or Game Blaster card to compare to so I don't know how accurate the sound output is but it sounds pretty good to me.
Here are some quick recordings I made:
Compatibility appears to be very good. So far the card has worked in everything I have tried including Bubble Bobble which I understand doesn't normally work when using a Sound Blaster with the CMS chips.
The board layout and Eagle project files for my prototype is available here if anyone is interested.