Every so often a customer is having problems with optical on our TubeDAC-09. Optical is not the most stable of connections as many manufacturers have the same problems. Here is a pretty typical troubleshooting method we use, with no assumptions on your knowledge of the issue.
-When playing a CD from your CD players, see if their is a red light at the end of the optical cable with a CD playing before plugging into the TubeDAC-09. Some players need to be told to transmit digital data (typically DVD players though).
-Make sure the clear plastic protective covers are removed from the ends of the optical cable(s).
-Make sure the optical cable has snapped (or is firmly) into place on the TubeDAC-09.
-make sure you have selected the right input on the DAC and have the volume turned up 
I find around 6 out of 10 is about nominal volume. As of mid last year the TubeDAC-09 has shipped with the volume control active and controlling all outputs.
-If still no sound from optical, check the USB input by hooking up your computer to the TubeDAC-09 with a USB 2.0 (USB Printer) cable. If it is your first time using USB audio on your computer your OS will take about a minute to install the USB audio driver, with out any action from you hook it up. Use the same USB port for the TubeDAC-09 after that and it is truly plug and play.
-If still no sound form the USB, then there is likely and issue with the TubeDAC-09, if you have a source with a coaxial digital out try that, if not, you can go inside and see if any of the white computer style cable connectors have come loose from shipping handling. Be careful not to bend any of the wiring too much as most of it is fine silver.
If nothing from the above is working you will need to send it back for testing or repair or replacement. As I mentioned before, I have had a few occurrences where the optical has been reported non-working, yet works fine when returned here
Cheers,
Ian
