Simple analog to s/pdif circuit needed for lab experiment.

[djsbriscoe]

Hi,
I am new to this forum and thought I would ask for some advice.
I need to send audio digital data down a 75 ohm coaxial cable and
recover it at the other end. This is work I am doing in my role as a university technician. The aim is to demonstrate how cable impedance mismatch can affect signal integrity.
I do not need the ultimate in audio fidelity, just something simple that works.
I am about to build the s/pdif DAC project (project 85 Elliott sound products) at http://sound.westhost.com/project85.htm for the receiver bit.

Now all I need is an analogue to s/pdif circuit that will work with the above as a transmitter. I have found this http://www.electricstart.de/site/atospdif.htm
but the crystal devices are obsolete. Can anyone suggest a similar circuit with readily available parts?
I have also considered an Elektor project (USB audio codec with s/pdif)
at http://www.elektor-electronics.co.uk...rchText=s/pdif
but this involves the use of a computer and a usb port.
Any advice would be very welcome.

David.

[rfbrw]

Try this and this. as
examples of the kind of thing all the major audio ADC manufacturers have on their websites. For something simple, it just a matter of availability. Once you choose your device, the odds are there will be an associated evaluation board along with schematic you can work from.

AKM
Analog Devices
Cirrus Logic
Texas Instruments
Wavefrontsemi
Wolfsonmicro

[jaycee]

Use CS8406 for an S/PDIF transmitter and CS8416 as the reciever. You should be able to link pretty much any audio ADC/DAC pair to these. They are available in SOIC format which is fairly easy to solder.

You have quite a wide choice of audio ADC and DAC chips. Sticking with Cirrus Logic, CS4334 should be "good enough" for the DAC if you really dont mind quality. CS5351 seems to be a pretty simple ADC.

The data sheets for all these chips usually have "sample applications" which get you up and running pretty quick. They aren't the best in performance but they will get you something that works.


edit:

Checked my links and found this website:
http://www.beis.de/Elektronik/ADDA2496/ADDA2496.html

He seems to have used the chips i've mentioned too

[drlava]

Radio shack was selling these for $8 clearance about a year ago, many are still popping up on ebay. They do just what you are looking for - convert a stereo analog signal to digital PCM or toslink, and do it 'good enough for demonstration'.

They can be improved with a slight circuit modification or two.

Contain the chips:

TC9287AF (adc mode) and TC9271F (transmitter/encoder).

I have used the CS8416 as the receiver (I2C mode) for this transmitter with fine results.

Datasheets attached:
Hmm maybe not, it's 1.2MB.