USB Audio DAC mod + LaserBoy Correction Amp

[buffo]

I had a feeling it was a signal ground issue.

Ok - now that you've got a symmetrical pattern you can start playing around with the size. There should be an input gain adjustment pot on your scanner amps. (Note: don't confuse input gain with SERVO GAIN, they are completely different! Adjusting servo gain will change your tuning, while adjusting input gain will not.)

Increase your input gain adjustment on both amps until you get the pattern scanning as wide as you had it with the DMX board hooked up. (Note that you may not be able to get the scan angle to be quite as wide.) Just make sure that they are adjusted evenly so that the image remains symmetrical.

Then run some shows and see how they look!

Adam

[DPSS]

Thanks Adam,

So you're telling me it's a normal thing to have to connect the signal ground to both the ground and negative terminals on one of the amps and that it doesn't mean there's something setup wrong or damaged I'm correcting by doing it?

[drlava]

Yep, that's normal. A floating input will usually cause issues.

[DPSS]

Ok, thanks drlava , but there's still something not right.

I tried adjusting the input gain pot on each amp while scanning the Spaghetti ilda test pattern, and found out the Y channel was allready at max (I can only set a lower scan angle) and the X channel can only be adjusted about 1/3 wider and ends up distorting the patterns corners when set at max.

Domingo.

[drlava]

the ILDA test pattern is only supposed to be scanned at 8 degrees or less.. Other than that... did Dave get back to you? It's possible that your scanner amps dont' have the gain range to get full swing from only +/-5V.

[hibbity]

http://cgi.ebay.com/6-CH-5-1-optical-Controller-USB-Audio-Sound-Card-S-PDIF_W0QQitemZ220382967806QQcmdZViewItemQQptZLH_De faultDomain_0?hash=item220382967806&_trksid=p3286. c0.m14&_trkparms=66%3A2|65%3A16|39%3A1|240%3A1318


is this the same usb sound card?

[DPSS]

Yes it is. This is the one I bought, it's a little cheaper:

http://cgi.ebay.es/USB-6-Channel-5-1...713.m153.l1262

The only difference I found between mine and the one shown at the begining of this thread is the board layout, but I was told here in the forum it's still the same soundcard.

Domingo.

[buffo]

I think Andrew is right - the ScanPro 20's are probably running as wide as they can with the single-ended output of the sound card correction amp. (Differential signaling will give you 4 times the peak-to-peak voltage.)

You could upgrade to a different controller that supports differential output, or you could live with the smaller scan angle...

Adam

[keeperx]

when i play wave files i gat a SUPER WIDE scan angle. when i play it thru spaghetti its WAY SMALLER.. i think it may be something in the driver or spaghetti.

[drlava]

(Differential signaling will give you 4 times the peak-to-peak voltage.)

Twice, +/- 5V verses +/-10V, or 10V peak to peak with single ended, 20V peak to peak with differential.

My ScanEco 30's have enough adjustment range to do fine with +/- 5V single ended, so I wouldn't expect the scanPros to have an issue, but it's possible that's why you should ask the seller.