Hi. I am trying to rig something up to control some laser show hardware. I need to end up with 8 analog channels less than 30Khz. Since this falls within the audio range I am thinking of using a multichannel WAVE file to control the channels.
I would like to use the SPDIF output of a soundcard and build some type of circuit that converts the 8 channel SPDIF output to 8 analog signals. I would assume that the same type of thing has already been done for obtaining 7.1 audio. Does anyone know of a schematic or circuit that I could look at as an example? I have found circuits for 2 channel (L & R) but I need to see a multi channel example. I am not a good electronics designer but I can usually following a shematic if one is presented.
Thanks,
Gary
I would like to use the SPDIF output of a soundcard and build some type of circuit that converts the 8 channel SPDIF output to 8 analog signals. I would assume that the same type of thing has already been done for obtaining 7.1 audio. Does anyone know of a schematic or circuit that I could look at as an example? I have found circuits for 2 channel (L & R) but I need to see a multi channel example. I am not a good electronics designer but I can usually following a shematic if one is presented.
Thanks,
Gary
I'm not quite sure I see the part of this problem that you're trying to solve via a 'complicated' transmission mechanism. There are many soundcards out there that already have 8-channel analog outputs without the need to do anything further. What is driving you towards wanting to use SPDIF or some other 1-wire protocol and an external converter? Is there a long wire run you need to handle or some other constraint in place?
The Emu 1212m outputting ADAT to a Behringer ADA8000 would be relatively inexpensive as far as external solutions go, but still over $300. A plain-vanilla 8-channel soundcard will run you somewhere between say $80 and maybe $250 depending on the specifics of OS, quality etc you need to work with. The OEM M-Audio cards at newegg or the Azentech X-Meridian are examples of things that should work reasonably well.
The Emu 1212m outputting ADAT to a Behringer ADA8000 would be relatively inexpensive as far as external solutions go, but still over $300. A plain-vanilla 8-channel soundcard will run you somewhere between say $80 and maybe $250 depending on the specifics of OS, quality etc you need to work with. The OEM M-Audio cards at newegg or the Azentech X-Meridian are examples of things that should work reasonably well.
The laser board needs 6 channels of 0-5v. I could use a slightly modified 5.1 soundcard to do what I want (and I actually already have) but I want 8 channels so that I can put stereo music on channels 1&2 to have a completely synchronized sound/laser experience. I haven't seen a cheap soundcard with 8 analog outputs, though. The one I have is CM106 based and does allow 7.1 audio but only through SPDIF. That is why I was asking about the SPDIF decoder. But, if AC3 won't work for me then I will abandon that idea.
I am not familiar with the ADAT format. I'll have to look into it more. Are there any relatively inexpensive cards that can send this format? A USB soundcard would be even better so that I could plug it into a laptop.
Thanks for all of your help and ideas.
I am not familiar with the ADAT format. I'll have to look into it more. Are there any relatively inexpensive cards that can send this format? A USB soundcard would be even better so that I could plug it into a laptop.
Thanks for all of your help and ideas.
An 8 channel analog out soundcard would work but I haven't seen one. If you have a link to a specific one that would be cool.
But even so, the soundcard would have to be modified to bypass the output capacitors so would require inserting a modified piece of hardware inside the computer. And, if someone else wanted to do this, it would require finding and buying a soundcard and then modifying it.
The S/PDIF route would have been nicer because a PCB could be developed that has all the hardware you need on it (decoder + DAC) and anyone could build one and they would just need to plug it into any soundcard with SPDIF output. No need to find, modify, and then place a questionable piece of hardware into a $1000 computer... and also, it would allow hooking up to laptops. So in short, a solution based on SPDIF would have been nice.
A USB/ 8ch DAC board would be the best solution, though.
I am not sold on a certain solution. My only requirement is that a complete solution under $100 or so and that it be portable. There are already professional solutions that cost $100s of dollars but I want to develop something that the hobbyist can afford and build at home.
But even so, the soundcard would have to be modified to bypass the output capacitors so would require inserting a modified piece of hardware inside the computer. And, if someone else wanted to do this, it would require finding and buying a soundcard and then modifying it.
The S/PDIF route would have been nicer because a PCB could be developed that has all the hardware you need on it (decoder + DAC) and anyone could build one and they would just need to plug it into any soundcard with SPDIF output. No need to find, modify, and then place a questionable piece of hardware into a $1000 computer... and also, it would allow hooking up to laptops. So in short, a solution based on SPDIF would have been nice.
A USB/ 8ch DAC board would be the best solution, though.
I am not sold on a certain solution. My only requirement is that a complete solution under $100 or so and that it be portable. There are already professional solutions that cost $100s of dollars but I want to develop something that the hobbyist can afford and build at home.
out of interest, why audio? how are the lasers controlled exactly?
I think that really, you are SOL so far as using sound cards go. USB cards are typically stereo only, until you start talking about USB 2.0/Firewire pro-audio stuff, and thats going to be expensive and overkill - and still have DC blocking. You could always pick up a pair of cheap soundcards that have front/rear outputs and use those... but then youd have to have software to play 4 channels on one, 4 channels on another... and... well the simplicity has gone.
I think that really, you are SOL so far as using sound cards go. USB cards are typically stereo only, until you start talking about USB 2.0/Firewire pro-audio stuff, and thats going to be expensive and overkill - and still have DC blocking. You could always pick up a pair of cheap soundcards that have front/rear outputs and use those... but then youd have to have software to play 4 channels on one, 4 channels on another... and... well the simplicity has gone.
Laser show scanners are controlled in the range of 40K points per second or less. And, they use analog voltages (X, Y, and R, G, B) for levels. Similarly, soundcard work in the range of 40K samples per second and have analog voltages. Do you detect something in common?
It is definitely doable... and has already been done. Check out this webpage as an example:
http://www.akrobiz.com/laserboy/
I have a $35 USB soundcard with 6 outputs. If only I had 2 more I would be in business! It is based on the CM106 so COULD have 8 outputs but for some reason the cheap soundcard makers are leaving out the last two because they figure 5.1 is all you need. It does pass 7.1 through the SPDIF port, though... which brings me back to my original notion of somehow making a SPDIF DAC that would allow 8 channel output.
But anyway, I know that what I want to do will work. But I just need to figure out how to put all the pieces together to do it the way I want.
It is definitely doable... and has already been done. Check out this webpage as an example:
http://www.akrobiz.com/laserboy/
I have a $35 USB soundcard with 6 outputs. If only I had 2 more I would be in business! It is based on the CM106 so COULD have 8 outputs but for some reason the cheap soundcard makers are leaving out the last two because they figure 5.1 is all you need. It does pass 7.1 through the SPDIF port, though... which brings me back to my original notion of somehow making a SPDIF DAC that would allow 8 channel output.
But anyway, I know that what I want to do will work. But I just need to figure out how to put all the pieces together to do it the way I want.
Thanks for the tips. I'll have to keep an eye out for a cheap card with 8 analog channels out on Ebay. I don't want to waste money... although I guess I could get one from Fry's and take it back if it isn't what I need. 
If the .1 channel is filtered that might not be a problem since I could use it for controlling things like fog machines or strobes that don't need a high rate of change.
If the .1 channel is filtered that might not be a problem since I could use it for controlling things like fog machines or strobes that don't need a high rate of change.
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