simple a/d to d/a circuit using cheap stuff. how do i start?

[big bustle]

so i want to build a circuit that has an a/d to d/a conversion.

i'd like to specifically add really bad digital audio artifacts to the signal so i'd like a chip/chips that can operate at 6 bit or 4 bit resolution that hopefully don't have input filters to get lots of aliasing

how do i start?

i found the tlc549 chip from ti.

says it samples at 8-bit blah blah blah

how do i connect that to a d/a chip and get some output?

i know the tlc549 is an 78-bit but after hours of googling it all i found

http://focus.ti.com/docs/prod/folders/print/tlc549.html

i don;t know where to start with this stuff

i read the stickies at the top of the forum and while the links are full of theory i don't know what connects to what.

[Blue_Toad]

Hi fucdemas,

I might be able to help but I need to understand what exactly you're looking for, I'm guessing you're looking to do something like this.

A/D (Making a bunch of aliasing) -> D/A

with nothing in the middle right?

[big bustle]

hey blue

I'm guessing you're looking to do something like this.

A/D (Making a bunch of aliasing) -> D/A

that's pretty much the basic idea for now

if anything a basic primer on digital circuits for audio would be nice.

i assume there are standard frameworks that have been used and many devices are interchangeable.


i was placing an order with futurlec and decided on a whim to buy a TLC7524CN dac

(while googling i found this link which seems to be an entire course on DSP construction)

http://www.ece.unh.edu/courses/ece649/documentation/index.htm

and this: and aTLC549CP ADC

i was going to look at the data sheets and just see what happens when i connect the 2.

i figured it was a place to start


i do need to find chips that sample at a really low bit rate or have adjustable bit rates. i google while the other day and found nothing

[Blue_Toad]

It's a good place to start, as long as you get the CS and WR lines right it will pass through the AD and into the DA, without a low pass on the output of the DAC there will be a little high end distortion but other wise should be basically a pass through as long as you hook it up basically like the notes later in the data sheet.

If I can help, let me know,

BlueToad

[big bustle]

thanks for the response!

what are CS and WR lines?

[MoltenVoltage]

analog devices sells some sort of bit reducer chip that i've been meaning to order

if you've never checked out bug brand stuff you should - he makes some really cool bit reduction things and posts (or used to post) schematics for everything

[alanlan]

You could also consider using A/D and D/A with more bits, say 12 or 16 and then having switches to disable certain data bits to really screw up the signal.

[big bustle]

ok so i'm back on this project.

i am at a loss on how to connect these two chips

my ad is the tlc549cp
datasheet: http://focus.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=TLC548

my dac is the tlc7524cn
datasheet: http://pdf1.alldatasheet.com/datasheet-pdf/view/28932/TI/TLC7524CN.html

i found this article on how to interface the tlc549 to the msp430

http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=slaa112

this seemed like a good place to start to figure out how to do this. i wired up the tlc like this but couldn't figure out what the DAC needed.

here's an image for anyone that would like to use mspaint to show me how to get these things to work.



alanlan: if you could point out how to wire switches to mess up the signal that would be awesome

[free electron]

The problem is, that TLC549 is a serial output ADC with SPI interface, where TLC7542 is a parallel input DAC. You can't connect them directly. You'd need some additional logic to convert the serial SPI signal into the parallel bit representation (shift registers).
You need  a parallel output ADC and parallel input DAC to get them work connected directly. Then you could also do some bit messing with the switches.
Here's the idea:

[big bustle]

The problem is, that TLC549 is a serial output ADC with SPI interface, where TLC7542 is a parallel input DAC. You can't connect them directly. You'd need some additional logic to convert the serial SPI signal into the parallel bit representation (shift registers).
You need  a parallel output ADC and parallel input DAC to get them work connected directly. Then you could also do some bit messing with the switches.
Here's the idea:

wow thanks for the tip! the whole digital world is just one big mess of confusion for me! the more i read the more questions i have. i might order these chips and go from there.