USB Audio DAC mod + LaserBoy Correction Amp

[DPSS]

So it's a problem of the scanners not being properly tuned? Are you sure?
When I hook up the DMX board that came with the scanners and have them display the patterns stored on it, they look perfectly simetrical. If it was bad tuning, wouldn't the images stored on the DMX board suffer the same problem?

[drlava]

Yes, I would expect so. Do you know how fast the 'circle.wav' is scanning? I haven't used that one before. If it's scaning very fast then the tuning imbalance might be in dampening not gain, which would make the DMX look OK but not the circle.

[DPSS]

I'm not sure how fast it's scanning, I generated the wav file myself with Laserboy, here's the file's header info:



Domingo.

[keeperx]

48000 samples per second.. or in this case 48000 unique points per second.

for a circle thats fine..

my SP20s do that..

[mixedgas]

[QUOTE=keeperx;92017]48000 samples per second.. or in this case 48000

Nope. divide samples per second by points in the image.

Thats your PPS to a first order approximation.

Steve

[DPSS]

I've generated a new circle.wav file lowernig the sample rate to 20000 and the problem still persists.
There just seems to be no way for the Y channel to scan as wide as the X.

[keeperx]

CORRECT ! ! i had the EXACT same issue...

Just adjust the master gain until they are correct. thats what im trying to tell ya

[drlava]

If your DAC gains are set properly like you say they are, both +/- 5V, then it has to be the tuning. You should try one of the free old versions of Spaghetti there are a few test frames in there. That way you won't have to rely on wav playing. Don't just use a circle, man, that only gives a small amount of info. Try the ILDA test frame for example.

[keeperx]

i ran in to this issue when i decided to re-tune my scanners..

i wonder myself if this is an issue with the SP20s and using single ended inputs.. but everyone tells me its not.

then i thought it was a power supply problem..

i racke mu brain for a long time till i just said F' it and set the master gains to compensate..

[buffo]

Only problem I see is that he says that when he connects the scanners to his DMX output board, everything is symmetrical. If that's the case, then the problem is *not* with his scanner amps.

I don't think this is a tuning issue. I think it's a problem with either the volume level on the sound card DAC or a problem with the adjustments on the correction amp.

True, adjusting the master gain on the Y scanner amp will correct the problem, but when he connects the DMX board, the problem will be back.

I think Alec is right... Time to get an oscilloscope.

Adam