Tosslink NOOB question!

Hi If I use tosslink wire to AVR how many channels will I get on the output?
Toslink is limited in bandwidth. I believe your receiver can take some information from the 5.1 and process it for the extra two channels. I don't believe you can pass high definition signals in 7.1.
toslink shares the same specification as digital coax:  S/PDIF.  It can transfer anything that the S/DPIG specification can do.  I believe this is limited at 24/96 for 2-channel PCM.  It can do the maximum bandwidth of old school Dolby Digital and DTS.  The Dolby Digital Plus format may have problems.  Obviously, it will not carry hi-res bluray audio formats Dolby TrueHD and DTS-MA HD.