Sound Card DAC Tutorial

UPDATE: Tutuorial has been updated with a complete wiring diagram and detailed tuning instructions from DrLava himself!

EDIT: drlava is presently sold out of full correction amp kits, but you can still buy bare boards from him. If you want a full kit, assembled or unassembled, you can get them from 300EVIL here: http://www.photonlexicon.com/forums/...696#post139696 These kits are a tad more expensive, but they include a very good 12V dc-dc converter (results in a larger scanned image) and a built in DB-25 connector. I highly recommend them. Wiring the 300EVIL amp is actually a bit easier than the drlava amp kits since the DB-25 output connector is already installed. All you need to do when using these is wire the connections between the soundcard and the amp.

I've tried to include everything necessary for construction of a soundcard DAC here in this tutorial. Many thanks to Drlava for his help and input. Hopefully someone finds this useful! Also, special thanks to Dean Hammonds for the original correction amp design.

This system is typically used with LFI Player show software as the free option, but there is other software available for sound card DACs at cost to the user. These are available online for download:

LFI laser player: https://sourceforge.net/projects/lfiplayer3d/

This tutorial assumes you already are familiar with soldering electronic components and very basic electronic theory and are comfortable building DIY kits. It also assumes you are aware of how to set up and install drivers for a computer USB sound card.

The most commonly used sound card for this setup is this cmedia sound card from DX. (the correction amp can be purchased here or here) The only other tutorial that talks about a sound card DAC on this forum uses the previous revision of this card. The most recent revision has slightly different connections, since it is an 8 channel card as opposed to 6 channels for the previous revision. Due to issues with buggy Vista drivers, I don't recommend using this sound card with any OS other than Windows XP 32bit or Linux. Any other sound card can be used as long as you feel comfortable finding the proper channel output capacitors to connect to on whatever card you might use.

For the DAC setup, we'll only be using the first 6 channels. You'll end up with the correction amp outputs connected to your laser modulation (up to three for RGB) and your galvo amps (to control X,Y movement).

The connections must be made on the positive side of each output capacitor so that we get a DC signal (you can see exactly where to connect in the closeup photo below).

In the following image, on the sound card, the connection points are as follows:

Blue wire = L Front channel
White wire = R Front
Yellow wire = L Rear
Red wire = R Rear
Black wire = Center
Orange Wire = Subwoofer
http://laserpointerforums.com/member...d-card-dac.jpg
http://laserpointerforums.com/member...ac-closeup.jpg


On the correction amp board there is a row of input pins. The first two pins are labeled 5V and Ground, and the last pin is also labeled Ground. Both these ground connections must be connected to ground for the correction amp to work. The middle G is a redundant ground pin on the correction amp, so it needs no connection. On the USB sound card board are some solder points right behind the USB connector that can be used to supply power to the correction amp.
The power connections to the correction amp are as follows:

Red wire = 5V (pad furthest to the left)
White and Black wires = Gnd. (both pads furthest to the right)

The connections can be seen in this image:
http://laserpointerforums.com/member...onnections.jpg


The defaults in most software are as follows:

Soundcard channels | Scanner function | Soundcard Pin in Picture Below (looking from left to right.. you can also see my channel labels written on the card)

Left | X galvo | 1
Right | Y galvo | 2
Left Rear | Red Laser Modulation | 3
Right Rear | Green Modulation | 4
Center | Blue Modulation | 5
Subwoofer | Intensity | 6
http://laserpointerforums.com/member...ac-closeup.jpg


Here's a complete wiring diagram:
http://i80.photobucket.com/albums/j1...ingDiagram.jpg

You have to go into the settings for the sound card (which you access through the little white and blue icon in the system tray in the case of this specific card) and set it to 6ch. By default it is set to stereo 2ch, which will not work. 2ch does not allow for your modulation channels, and using the DAC in 2ch mode will make it impossible to tune.

__________________________________________________ _____________
NEW!!

Here's tuning instructions direct from drlava himself:

Tuning the sound card DAC correction amp:

Tuning the amp is simpler than it looks. There are 6 channels, but only two adjustments per channel, and each channel is adjusted the same way. Tuning only needs to be done once after construction of the audio card DAC.

First, a note of caution: Never plug in or unplug the USB sound card while your projector is on and connected to the DAC. Doing so will cause the sound card DAC to produce out-of-spec voltages that may cause dangerous beams to shoot out of your projector.

Tuning the sound card DAC. Needed: multimeter, small flathead screwdriver, max.wav, wires.

1) plug in the sound card DAC, open the control panel for the sound card and set it to 6 channel mode.
2) Set the wav and output volume to max, mute all others, and confirm no 'effects' are on, and each speaker gain is set to 0dB.
3) In the windows 'Sounds and Audio devices' control panel, 3rd tab, verify your sound card DAC is the default device.
4) while no audio is playing, connect your multimeter in volts mode between the output G and output channel 1. Adjust the channel 1 Offset pot with your screwdriver until the meter reads 0 volts.
5) repeat step 4 for all 6 channels.
6) play max.wav in windows media player, repeat on, volume all the way up. Measure the voltage between output G and output channel 1 and adjust the channel 1 Gain pot till your multimeter reads either +5V or -5V (adjust to whichever it is closest to)
7) repeat adjustment in step 6 for all 6 channels while max.wav is playing
8) stop windows media player, and exit. Go back to windows 'Sounds and Audio Devices' control panel, 3rd tab. Set the default playback device back to your normal audio card.

That is all the hardware adjustment that needs to be done. Later I can write about setting up Laseroids with EzAudDac and the sound card DAC.
Happy lasing!

If you have trouble playing max.wav, download and install the AC3 decoder here. (thanks to MISTERWILLING for pointing this out) The AC3 decoder is not free, but should work long enough to accomplish the tuning. If it's not sufficient, You could probably also use klcodec pack.

There have been reported issues with the supplied cmedia sound card drivers. If you experience issues with jumbled output from the DAC, make sure you are using this driver: CMEDIA AUDIO DRIVER

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The soundcard DAC comes with a +-9V DC-DC converter. This will limit the scan angle that is possible with the DAC. I highly recommend replacing the DC-DC converter with one that supplies +-12-15VDC such as this: 580-NKA0512SC This is a drop in replacement for the correction amp board which will vastly improve the scan angle.

Here's the complete setup:
http://laserpointerforums.com/member...d-card-dac.jpg

Here's a diagram of how the PC, DAC, and scanner get connected:
http://laserpointerforums.com/member...ner-layout.bmp
To maintain the ILDA standard in your system, you'll need to install a DB-25 connector on the DAC to connect the DAC to the scanner. Here's the pinout for ILDA DB-25 connectors:
http://laserpointerforums.com/member...-rgbpinout.png

Here's some video of the completed DAC in action:
http://i80.photobucket.com/albums/j1...RGBAnalog2.jpg
http://i80.photobucket.com/albums/j1...log3bright.jpg
http://i80.photobucket.com/albums/j1...rdDACdemo2.jpg
http://i80.photobucket.com/albums/j1...ardDACdemo.jpg

Anyone with questions can PM me or email me at faze4djs@yahoo.com.

Maybe a little tip for improvement:

If you wire an SPNO relay in the interlock loop (between A and B) which is driven by the amp's power supply, the interlock will only be active if the DAC is plugged in. Unplugging the DAC will break the interlock and shut off the laser.

The relay need not be heavy current, maybe even an optocoupler is enough to do the job.

Nicely consolidated info- thanks! (I know what you mean about the other threads)
I thought I might paste in a sample of the EzAudDac.ini file, the file that goes in the same directory as your EzAudDac.dll. It provides an easy way to tweak custom configurations.

*********************************************

[Sound Card Selection]
UseCardNumber=2

LowLatencyBuffering=no
;not all programs work smoothly with minimal buffering, try yes if you have a hyperthreading
; or dual core computer and like to try to speed up timing.
; yes works with zoof games, LDS, HE-Laserscan
; no works best with LazyMame, LFI player

SampleRate=48000
;choose a standard samplerate that your card can handle 44100, 48000, 96000 etc.


RepeatFrameWhenOut=no
;'yes' or 'no'
;Repeats the last frame displayed if the program doesn't feed another frame in time
; if 'no', then the DAC output goes to 0 until a new frame is fed.


BlankDelay=5
;enter the number of points that the laser blanking should be delayed.
;enter 0 for galvo based blanking, 3-7 for solid state or AOM blanking.

[Channel Invert]
;enter 'yes' to invert the channel output, 'no' otherwise.
X=no
Y=no
R=yes
G=yes
B=yes
I=yes

[Channel Selection]
;Enter the desired output chanel number (1-8 only) of the signals:
X=1
Y=2
R=3
G=4
B=5
I=6
AL=7
AR=8

I built my own correction amp in the meantime, but I'm still a little wondered about the blanking.

There is both an 'Intensity/Blanking' signal and an intensity signal for each separate laser. Which one does the actual blanking and which ones should I wire to my laser drivers?

BTW, the laser intensity outputs are specced by ILDA as being 5V differential outputs. On channels 3-6, the gain should therefore be set to read +/- 2,5V, not +/-5V, to operate within ILDA specifications. See:

http://www.laserfx.com/Backstage.Las.../ISP-DB25.html

Your mileage may vary with different laser driver circuits, though. Another option is to correct the gain for +/-5V and lower the volume control for the channels with 6dB.

Quote:

---

Originally Posted by ElektroFreak

The soundcard DAC is single ended rather than differential, so in that regard it isn't ILDA compliant. I'm not sure that those specifications apply to this DAC.

---

It's true that the sound card coupled with that particular correction amplifier board isn't ILDA-compliant, but I want to clarify that this is no limitation of the sound card. It's easy to make ILDA-compliant, differential outputs the same way that most commercial DACs including Riya, EasyLase and Pangolin FB3 XE do. Those commercial DACs don't use underlying DAC chips with differential outputs either!

Quote:

---

Originally Posted by ElektroFreak

Would you be willing to post the schematic you posted in another thread here as well? That way people can see the circuitry involved..

---

Of course, I should have realised to post it here too: http://www.photonlexicon.com/forums/...&postcount=349

Quote:

---

Originally Posted by ElektroFreak

The soundcard DAC is single ended rather than differential, so in that regard it isn't ILDA compliant. I'm not sure that those specifications apply to this DAC. Also, I've never seen a laser that can be modulated by a negative voltage. Most if not all direct modulation lasers use either 0-5V TTL or 0-5V analog. The soundcaed DAC supplies exactly that. I might be misunderstanding what you're saying, though.

---

Remember that the laser's modulation ground need not be the same as the ILDA ground and cable shield. With a differential output, both of your lines have a high impedance (floating) with respect to ground and the projector chassis, you just connect the negative signal to your laser's modulation GND, and the positive signal to the modulation input.

On the soundcard DAC, all of the negative outputs are essentially hard-wired to ground (since they're not there!), this will make the connection a little more sensitive to noise over longer distances and half your laser output and scan angle. Making the outputs differential is an easy fix, though.

Remember, ILDA was designed as a low-impedance system (100 ohms), but we're driving it as a high impedance connection with the correction amp.

I put together a soundcard amplifer using DrLava's bare PCB board... (DrLava is a hero btw). It works like a champ with once concern. While I'm tuning the channel 1 offset, the voltage jumps around like mad. Say it's reading 0.1 and I start turning the offset screw, it will jump to -10.05 and then when I stop, it goes back to the right voltage. I can get it adjusted OK, but it seems weird to be getting these fluctuations while tuning. My concern is somehow during normal usages, it might send an out-of-spec voltage to the scan amp and cause damage.

Thoughts?

Thanks,
Mike

Hi Bowfly thanks :) it sounds like you have a bad solder joint below that pot or in the area, touch them up with a little flux and solder and it should be stable.

Sure enough, one joint on the pot hardly had any solder. Quick touch up and the offset adjustment is steady. Swaaweeet!

Thanks!!!!
Mike

Great post.
Thanks from all of us sound card users.

Can I use an I-show dongle with spaghetti ?

I hear you . ta

Quote:

---

Originally Posted by ElektroFreak

Subwoofer | Intensity (not used with spaghetti) | 6

---

if your like me and using the sound card dac to play back shows captured from ADAT 6 is usually SMPTE data... not that many people are playing back old ADAT recordings, but you know, just throwing it out there lol

if anyone DOES have old ADAT recordings... best way to transfer them is anything with a light pipe input... I use the setup at the planetarium, old adat deck hooked via light pipe to an ADAT HD24 hard disk based recorder, record the atat onto the HD24, remove hard drive, put into pc and use software to rip the WAV files off of the ADAT hard drive...

then I recombine them into 8 Channel FLAC files (lossless compression) using Audacity, and then I can literally just "play back" the ADAT out the sound card dac... its very cool being able to watch all the old ADAT shows (that can be up to an hour long or so) without having to wait for long load times between songs... (a-la LC-ADAT)

Hi,
I'm very new at this but I followed this nice tutorial. I had to make my own corr amp as the recommended board were sold out. I used some lm324 quad amp and followed the schematic at
http://www.akrobiz.com/laserboy/grap...laser_h_95.jpg

I calibrated as said, 0-5v and such. I have a 20kps galvos off a ebay, some china thing and am able to make circles and such using a 600hz sine etc...

When I use the LFI player, it looks really bad. I read the manual and tried everything. Nothing is recognizable. Any idea what I am missing?

I did have to update the .ini file as the channel 2 on my sound card (right) went bad so I use channel 5 to drive y. so I have

x=1
y=5
r=3

The rest I do not need as this is a single color setup...

Can anyone help? Thanks very Much Luke

I did that too. I wonder if the LFI player likes me using channel 5 to drive my X coordinate?

here is a copy on my ini file...

[Sound Card Selection]
UseCardNumber=2

LowLatencyBuffering=no
;not all programs work smoothly with minimal buffering, try yes if you have a hyperthreading
; or dual core computer and like to try to speed up timing.
; yes works with zoof games, LDS, HE-Laserscan
; no works best with LazyMame, LFI player

SampleRate=48000
;choose a standard samplerate that your card can handle 44100, 48000, 96000 etc.


RepeatFrameWhenOut=no
;'yes' or 'no'
;Repeats the last frame displayed if the program doesn't feed another frame in time
; if 'no', then the DAC output goes to 0 until a new frame is fed.



[Channel Invert]
;enter 'yes' to invert the channel output, 'no' otherwise.
X=no
Y=no
R=yes
G=yes
B=yes
I=yes

[Channel Selection]
;Enter the desired output chanel number (1-8 only) of the signals:
X=5
Y=2
R=3
G=4
B=1
I=6
AL=7
AR=8


I also am using a npn transitor to module some laser diode. It does not apper to work great but at least I should be able to see some pattern...

If you ever clicked ANY of the effects in the effect tab of the cmedia driver, you are going to have to reset those to defaults for it to work. This might mean re-installing the driver. Which cmedia driver version are you using? You might need to use the one linked in the tutorial.

I'm clearly a noob here and hopefully given the date people are still reading this forum, but I wanted to know how to communicate directly with the soundcard. I'm looking to send non-sound outputs without sending .wav files. Essentially can I get the soundcard to sit on one output voltage then switch to another when I want it to? Is there some software to allow this?

You send to the sound card the same as you would send anything to the sound card. If you are on Windows you have many choices from Win32 APIs to DirectX to XNA, etc. It's pretty simple to make this work if you have an understanding of those APIs.

No matter what you will be communicating with some kind of Windows abstract sound device and that will communicate with the specific driver for the actual hardware you have. As far as I know they all work about the same. There will be some address you send a big chunk of data to. If you want it to hold a state, you need an execution thread to keep filling up the buffer and dumping it to the device address over and over. You can't just set it and forget it, unless you want to set it to silence or digital zero.

Brilliant thanks. James; is it a matter of using an API as suggested by JohnVayas to communicate to the driver address? I guess I need to read up on APIs anyways...

Quote:

---

Originally Posted by james

No matter what you will be communicating with some kind of Windows abstract sound device and that will communicate with the specific driver for the actual hardware you have. As far as I know they all work about the same. There will be some address you send a big chunk of data to. If you want it to hold a state, you need an execution thread to keep filling up the buffer and dumping it to the device address over and over. You can't just set it and forget it, unless you want to set it to silence or digital zero.

---

Actually, you can set it and forget it depending on what you are doing. If you have a circular buffer you can load an entire frame and tell it to repeat and it will keep sending out the frame over and over. Not all that useful, though. But, if you have a big wave file you can load the entire wav file into a buffer and set it and forget it. But, for useful laser display you need the ability to adjust parameters in real time, which means changing the frame data as it is being sent. You can't send it after it is in the buffer but you can before it reaches the buffer. That's why you need streaming data and why you need to keep feeding the sound card in this case. There really is not sound card address that you send the data to other than the buffer that you define. What you actually do is full the buffer you create and notify windows that your buffer is ready and Windows will read it.

DirectX is the easiest API that is built into your computer. Look into what a primary and secondary buffer are and learn to use them. There are some 3rd Party libraries for dealing with audio a little simpler but they come with the overhead of license agreements and additional DLLs to install.

Yes. You fill a buffer that you have defined in user memory space (inside your own application) and tell Windows where it is. Then Windows takes care of moving that data (from an an address aka pointer) to stream it into the clocked DAC channels.

You can fill a buffer and tell it to repeat without having to maintain a running thread of execution? Really?

James. :)

I think this is a good place to plop this info that anyone following this tutorial will eventually benefit from.

I have some details regarding how to get your sound card driver working in windows 7 for the c-media chips that many folks use when making these. Windows will likely mix all of your audio channels together and by doing so send garbled signals to your sound card DAC. Having the correct driver has fixed this for me, this is what I did:

It seems that all devices with the cm6206 are compatible with the same drivers. It doesn't matter if it's a 5.1 card, 7.1 card or even if it's not even a sound card at all!! They put this chip in a LOT of different products and they all seem to be compatible with eachothers drivers.

None of the windows drivers properly separate the audio tracks. I have tried them all. At least all that I can find. The drivers that come with these USB sound cards also don't work. I have tried 2 different OEM disks and downloaded a few others that also don't work. If the driver installs 2 different devices in your windows audio control panel, it's the wrong one.

This is the only driver I have found to work:

http://www.rosewill.com/media/Downlo...207%20v1.0.zip

This is a zip file, so you have to download an unzipping program. Winzip or winRAR will both work. It might say it's the evaluation version, but I've had it for months now and it still works.

It's for a set of gaming headphones, but don't let that bother you. It comes with an applet for the audio driver that gives you access to more controls that just the standard windows control panel. When you install it, it should replace any other c-media, or windows universal USB sound device drivers (it did for me anyway). I just went into the folder where I unzipped the driver and navigated to /fscommand/W7 and double click on "setup". This automatically replaced the other driver.

If it doesn't work for you, go into your control panel and select the audio device that was first installed (I have done it for both devices when it has installed 2 and it doesn't seem to matter which one you choose).

Go to the properties window and again click properties.
Then click "change settings" and go to the "driver" tab and click "update driver".
Click "browse my computer for software" and click browse.
Navigate to the folder where you unzipped the driver that you downloaded and make sure that the "include subfolders" box is checked. and then click next. It should find the driver and update it.

Once you have the driver installed you have to go back into the control panel and select the new device that it added. It should be called "Speakers - USB Multi-Channel Audio Device".

Click configure and select either 5.1 or 7.1 depending on the actual sound card that you have.
Click next and make sure all of the boxes in that screen are checked.
Click next and again check all of the boxes for full range speakers.
Click finish

Now with the same device selected in the control panel view, click properties.
Go to the advanced tab and make sure that the default format is set to 16 bit, 48000 Hz (DVD Quality). Mine was set to 44000 Hz by default and this will make the laser images distorted.
Do not set this device as default!!! Leave your internal sound card as default. I also turned off system sounds to be on the safe side.

I have also seen a lot of people say that you need to go into your internal sound card device and go to the "Enhancements" tab and click the box for "disable all enhancements". I'm not actually sure if this is necessary since it should only affect system sounds but I did it anyway.

If the driver installed properly, you should also have a new item in your control panel main view in addition to "Sound".
You should see "USB Multi-Channel Audio Device" double click it.
This is where you will see at the top left under "System Input" a drop down box where you can select the number of channels. Select 8 even if you only have a 6 channel card.
Next, look down at "Output Mode" and the drop down should list the max number of speakers that are specific to your particular sound card.
I left all other settings as default.

OK! That's it. With this setup I am able to get Laserboy to output correctly to all channels without mixing things together.

I just got a copy of this a put it here:

http://laserboy.org/driver_for_rhts-...sta_7_v1.0.zip

James.

James, is that the driver as well for this type of external sound card?
Daderaide, thanks for that info.

I ran into a problem with my sound device that caused me to set it aside for some time but i found a work around for the fault i was having, mine was distorting one of the main stereo channels and i traced it to the final stage of the audio amp that would be used for a set of headphones, i switched the point where i take the audio and feed it to the correction amp and that solved that problem at-lest for now, i have since updated that computer to win10 but the sound card dac seems unaffected, now i just need to learn how to use laserboy, it seems to work just fine under winblows 10 but i need to play with it more

It's a copy of the driver daderaide just posted. It will be there as long as The LaserBoy Forum is there!

Much like, if you ask me, there is a copy of Spider Player install.

As far as LaserBoy goes, feel free to ask questions... probably best in The LaserBoy Thread.

James.