• everything at once

    tshen2 • 10/11/2014 at 22:32 • 0 comments

    there's a bunch of different ways for ordinary people to transmit wireless audio.

    nope! i'm kidding, you're stuck with Bluetooth audio. it is awful for these reasons.

    1. way too much transmitter hardware. you need a.. smartphone? or something smarter?
    2. complicated pairing process.
    3. way too much latency (time delay in transmission).
    4. you can only connect one thing to one other thing. proper wireless stereo is not an option.
    5. limited to 16-bit compressed audio. you want 24-bit lossless audio? no.

    that's miserable. are there other options?

    SPDIF is a lossless, low-latency, 24-bit digital audio transmission standard, but it is not wireless - it usually travels through RCA cables, and no one makes a wireless SPDIF transmitter. or do they?

    there's an analog video standard called NTSC. it's pretty low-quality (for video), and it also travels down RCA cables. and according to various sources, it requires 6MHz of bandwidth. SPDIF also requires 6MHz of bandwidth!

    so both of these signals are transmitted through 75Ohm RCA cables. and both of them require the same amount of bandwidth. is it possible that a wireless NTSC transmitter will transmit SPDIF just fine?

    these are reasons why NTSC transmitters can be bought for dirt cheap:

    • NTSC is old as heck, and NTSC equipment is obsolete by definition.
    • scale! people still use NTSC for security cameras and car backup cameras.

    so some digging on The Amazons revealed this gem. it is a short-range wireless NTSC transmitter-receiver pair. it is meant to connect a car's backup camera to a screen on the dashboard. it costs $12.

    experiment time.

    i want to send lossless 24-bit digital audio from my tinycomputer to my fancy home-made speakers. so here is the signal chain:

    1. NuForce uDAC-2: USB to SPDIF converter
    2. NTSC transmitter: to transmit SPDIF wirelessly
    3. NTSC receiver: to receive SPDIF wirelessly
    4. Gefen TV DAC: SPDIF to analog audio converter
    5. terrible homemade speaker electronics: analog audio to terrible converter

    does it work? yes. i can send lossless audio over a 7 foot distance for $12. here is a video of it in action.

    if you don't like videos, here are some photos.

    1. NuForce uDAC-2: USB to SPDIF converter

    2. NTSC transmitter: to transmit SPDIF wirelessly

    3 & 4. Gefen TV DAC: SPDIF to analog audio converter

    5...

    terrible terrible terrible

    Tshen2 2014