USB Audio DAC mod + LaserBoy Correction Amp

[carmangary]

He said he could replace them for me, but I really dont wanna have to send them back to china. No idea what shipping would be like

I just sent a laser to China from TX. Cost me about $32 for priority express with tracking.

[Hemlock Mike]

JamesL ---

Your first picture of the USB audio card shows six wires connected to the board on the back side. On top are six 100 mFd caps going to the output connectors.
Can the caps and connectors be eliminated or do the caps play some role in the unloaded circuit?

Mike

[keeperx]

DING DING DING

the caps are useless and actualy installed backwards

pop em off and you have nice easy place for soldering.. they are not needed at all...

[Hemlock Mike]

For low voltage audio, they have no polarity here. I don't have a schematic to know.

All that crap is coming off !!!

Thanks -- Mike

[DPSS]

Hi,

I'm having a little problem while adjusting the pots for the X and Y channels on my correction amp (+ USB soundcard DAC). For some reason the X channel can be tuned a lot wider than the Y channel. Here's a pic of the circle.wav file displayed using Windows Media Player 11 and with the pots on both channels set over the maximum width:



I have set the parameters in the soundcard's drivers as shown on page 3 of this thread for playing laserboy wav's with WMP so, as far as I know, that shouldn't be the problem.
Has this happend to anyone before?

[drlava]

It doesn't sound like you know what your output voltages are. that's step #1 in tuning these amps. Grab a multimeter.

Use wavosaur (or VLC player) and max.wav with a multimeter to set the 5V deflection. Wavosaur is much more accurate than WMP, which could be adding extra gain in a channel. Once you have the amps zeroed and 5V deflection set, don't touch the pots. From then on think about scanners gain.

[keeperx]

THAT is digital clipping.. im sure of it..

WMP is probably amping as Andrew said.

try turning the volume down and see if the circle becomes an actual circle.. it will be smaller but thats OK.

[DPSS]

It doesn't sound like you know what your output voltages are. that's step #1 in tuning these amps. Grab a multimeter.

Use wavosaur (or VLC player) and max.wav with a multimeter to set the 5V deflection. Wavosaur is much more accurate than WMP, which could be adding extra gain in a channel. Once you have the amps zeroed and 5V deflection set, don't touch the pots. From then on think about scanners gain.

I've set the pots as discribed for both the X and Y channels using VLC player and the max.wav file and this is what I get now when playing circle.wav with VLC:



As you can see, for some reason the X and Y channels scan at diferent angles.
The scan angle is arround 15º for the X channel and half for the Y channel.

THAT is digital clipping.. im sure of it..

WMP is probably amping as Andrew said.

try turning the volume down and see if the circle becomes an actual circle.. it will be smaller but thats OK.

I think you didn't understand what my problem is (or most likely I didn't explain myself very well ).
I know the image is cliped, I just tuned the pots over the maximum scan angle so you could see it's not a question of one of the channel's pots being set higher than the other one. If I turn the volume down, it does round of the edges but, as you can see in the pic, it's not a circle.

Domingo.

[drlava]

I've set the pots as discribed for both the X and Y channels using VLC player and the max.wav file and this is what I get now when playing circle.wav with VLC:

Good job, so now that you tuned both 0-offsets to 0 and max output to 5V, you know that the DAC is generating the same signal levels on each output. This means that now you must tune the scanners.
http://www.photonlexicon.com/forums/...ead.php?t=3707

[keeperx]

yeah.. so mess with the gain on the amps till it is...

better yet, send it to me and ill throw it on the scope and make sure all is well..

better even than that..
http://cgi.ebay.com/Goldstar-Oscillo...|39:1|240:1318
offer that guy 50 bucks and get one of your own.