Messages

1

DACs / Re: Genuine Extra Stimulus LaserBoy Correction Amp Boards!

« on: July 24, 2014, 09:45:30 am »

Well this project got put on the backburner due to summertime activities but I'd like to keep it moving along.

Is the preferred soundcard to use still at Dealextreme?

This laserboy DAC is going to be used with brand new ScannerMAX 506 scanners I just purchased from Pangolin.  Pangolin does not yet have their amplifiers available so I'm purchasing a modified one from Mixed Gas of Photon Lexicon.

These scanners are very fast, and I can't wait to drive them with Jame's DAC.

So if anyone has a part# or supplier for a good USB soundcard please let me know, because I'd like to keep my current soundcard on my breadboarded DAC and 1st projector.
There are going to be two projectors in the house by the end of this winter, I'm SO excited!  The dream of projecting beams and graphics at the same time is within grasp!

2

DACs / Re: Genuine Extra Stimulus LaserBoy Correction Amp Boards!

« on: December 10, 2013, 01:17:14 pm »

Thanks, James!  You are THE MAN!

3

DACs / Got my LaserBoy Correction Amp Boards

« on: December 10, 2013, 06:02:24 am »

Wow, in just a couple days this kit showed up at my doorstep complete with parts list.  It arrived packaged well with no damage, picture 1.  I was pleased to see a DB-25 connector with ribbon cable already attached to a header was included! 

I am very impressed with the included components and quality of the PCB, picture 2.

James even went through the trouble to specify colored jumpers (R,G,B,yellow) for the modulation correction amps!  Picture 3 and 4.

No schematic is provided, which for me is OK.  The board requires only +5VDC (How nice is that ?) and uses a DC-DC converter to provide +/-9 VDC. That eliminates the need for a power supply cuz the +5VDC comes from the USB soundcard.  The only thing I need clarification on is the part of the procedure to set up the offset bias.


From James post:
"With no signal, turn the voltage regulator pot (also 500 ohm) so that you are close to zero volts on all outputs. Look for the lowest voltage of all channels and make sure you are just a bit on the positive side.
 
If you measure the DC offsets directly from each channel of the DAC, you can measure the negative offset voltage from the test pin on the correction amp (V_off) and adjust it to be -1.5 times the offset you measured from the DAC channels. That will get you pretty close.
 
Let the thing sit for a while and settle. Re-adjust as needed.
 
Now with all the channels measuring some little positive voltage (from about 30 to 120 millivolts) you can trim out the offsets. Turning up each 500 ohm pot per channel adds a bit of negative voltage."

Looking at the traces the op-amps get -V supply from the adjustable LM337, which I think is provided to compenstate for different sound card offset voltages.  I'm assuming the op-amps all have a +9V supply.

James I am unclear on exactly what V_off is connected to and why it needs to be adjusted "to be -1.5 times the offset you measured from the DAC channels".

Can you expand on that a bit?

Its a great looking kit and I think I'll be ordering another, now the hobbyist can afford to project beams from two projectors and do that cross-over thing which looks so nice.....

-Jason
 

4

DACs / Yeaaaaah!

« on: December 05, 2013, 11:10:49 am »

Thanks for doing another run of these kits, James!  Man I tried ordering one of these a couple years ago from somewhere else (Dr Lava) and they were never in stock again.
Take a look at my breadboarded corrrection amp you are helping me finally get rid of after a couple of years!  Makes it really challenging to take my projector to friends house .... Gotta bring my schematics, a meter, etc cuz if a wire pulls out during transit sometimes it takes a little while to get it back in... LOL  Although I do admit I like the looks of the breadboarded circuit in a do-it-yourself fun way.
By the way... Are there any other fellow laser folks in the Chicagoland area ?
-Jason