does anybody know a high quality transmitter to transmit audio signals over a distance of about 7 meter from a digital output source (computer - coax or optical) to a digital input (DAC 1 - coax or optical)?
If your computer have WLAN you can use an AirPort Express.
Its not exact what you're asking for though, so someone else may have a more spot on solution...
I agree with krmathis - if you have a wireless network set up, you already have the ability to stream digital. An elegant solution on the receiving end would be a Logitech Duet or Squeezebox. Both units provide digital outputs that you could feed into a DAC.
What could be cheaper than an Airport Express (used even) and a 802.11 base station (used even). You don't need the latest technology, either, for bit-perfect transmission....