Wireless digital audio signal (coax)

My dad has a Philips 900 series set with DSS930 speakers (they are apparently quite famous). In Jan it will be his birthday so I would like to surprise him! Since the audio signal is sent to the speakers digitally and each speaker is fitted with an amp I believe it would be a great idea to send the digital audio signal wirelessly! Since it is a digital signal I believe it could be done without loss of quality… Now I am not sure about all of this but it would be great!

I am a bit of an electronics hobbyist getting started. As a kid already I was fascinated and I have decided that I would like to really get into it more. That means that my knowledge is limited…

Therefore I would like to ask some inspiration from whoever reads this. What I have come up with is simply applying the method of a virtual wire. I haven’t had time to really dive into this but do you think this would be okay? Also, would I have bandwidth issues? And what wireless frequency should I choose? I was thinking 2.4 GHz would be best because it has least interference from other signals & electronics.

Anybody reading and/or replying: thanks in advance!

What digital audio format is it?

Hey Leon_Heller,

The speakers may run independently on any digital coax out - I believe it is S/PDIF. It is uncompressed digital audio… Is that the info you asked for?

Hi Timvp,

I think one of the first problems you’ll encounter is the bitrate of the audio. I’m a bit fuzzy on S/PDIF, but at a 44.1 khz sampling rate at 16 bit samples (CD quality) you’ll get just over 1.4 Mb/s for a stereo signal, which is a lot of data to push over easy to use radios reliably, keeping in mind that not all packets will make it through, and you’ll need to either re-transmit them if you have the bandwidth and latency available, or drop the packet resulting in poor audio.

If you can create a decoder to split the stereo SPDIF signal into 2 mono signals, that would be about 700k/s, which would be more manageable.

I’ve gotta run to take my ferret to the vet, but I’ll be back to discuss later if you have questions.

Cheers,

Roko

S/PDIF is rather fast. You will need a special interface chip and a fast MCU, or a seriously fast MCU like an XMOS chip, to interface it to your wireless chip:

https://www.xmos.com/applications/software-components

It doesn’t sound as if you have the experience for this sort of project.

Nah, I don’t unfortunately… But what I do have is determination, good hope that it’ll work out and wits. I just need the shortest route to Rome. So, where do I start??

Start by obtaining the S/PDIF specification.

Do a search for wireless video transmitters. I’ve seen instances online of people using cheap WVTs to do what you’re seeking to do. Sure, it wouldn’t be home-brew but it would probably satisfy your requirements without having to re-invent a decidedly non-trivial wheel.

For example, just a shot in the dark:

http://www.shoptronics.com/5wiauvisetrb.html

You might want to look at Nordic’s nRF24Z1. It can handle S/PDIF input and output (AFAIK), and can transmit up to two channels at 16bits/48kHz.