Topic: Texas Instrument DACs

[Agent C]

Bit of background:  I'm writing my own laser software in Java with the Processing.org IDE/language abstraction - very cool, check it out if you don't know what it is.

I started with the onboard sound of my 4 year old powerbook just to get the fundamentals working in my software, and I use an old o-scope to check the output.  I recently switched to the ubiquitous 5.1 usb sound card and I noticed that the high frequency performance of the c-media chip isn't up to par with my onboard TI (TAS3004) sound chip.  Granted, I'll probably code out the high frequency stuff as I transition to actual laser display since it isn't good for the scanners, but it left me wondering if these TI sound chips would be a better route.  After some snooping around I found these beautiful usb evaluation boards from TI.

TAS3208 Low Cost Evaluation Module http://focus.ti.com/docs/toolsw/folders/print/tas3208evm-lc.html

6 channel audio out, 48khz, usb, $99.

TI makes some fancier chips like the 3108 that will do 192khz out, but they aren't paired with onboard DACs like this evaluation board.  Most also come with a DSP on die - not sure what we could do with that but I'm sure we could think of something!

~C

[James]

Hmmmm.

I was thinking it was the other way around!

When you said you could clearly see the dots on the scope with the USB card but saw lines from the note book, that to me is an indication that the USB card has much better high frequency resolution.

High frequency content in a waveform is a weird and illusive thing. It happens the instant there is a change in energy that is greater than the current trend of acceleration.

A simple triangle wave "sounds" pretty smooth, almost like a pure sine wave, but because of the abrupt change in dirrection at the sharp corners, it has an infinite series of harmonics!

http://en.wikipedia.org/wiki/Triangle_wave

There will be plenty of these kinds of "corners" in a laser vector drawing!

James. 

[James]

How to build The Perfect Sine Wave Generator, with ZERO percent total harmonic distortion, from only two common components:

Parts List:
1. A rock
2. A length of string

Instructions:
Tie rock to the end of a length of string. Fix the other end of the string to a stationary position such that the rock is suspended with no other objects near it. Swing the rock on the string. Enjoy perfect sinusoidal motion for hours!

This is such a beautiful thing! 

James.