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Old 25th April 2007, 05:08 PM   #11
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Join Date: Apr 2007
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.
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Old 26th April 2007, 10:33 PM   #12
jaycee is online now jaycee  United Kingdom
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Join Date: Apr 2004
Location: Norwich, UK
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.
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Old 26th April 2007, 11:23 PM   #13
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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:


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.
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Old 27th April 2007, 02:44 AM   #14
Chartal is offline Chartal  Canada
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Location: Montreal
Some Sound Blaster Audigy card have discrete 7.1 channel outputs.
But i don't know if the sub channel (.1) have a low pass filter on the card.
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Old 27th April 2007, 05:17 AM   #15
weissi is offline weissi  Europe
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maybe something like this... http://www.club3d.nl/index.php/produ...eatron/item/12
regards / servus
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Old 27th April 2007, 12:50 PM   #16
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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.
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