I'm hoping someone can help.

I'm running a Toslink module into an original Buffalo DAC (ES9008) and I'm getting an optical signal from an Airport Express. Every so often the DAC will experience a digital glitch. It's not a click or pop, and the lock LED stays lit, but there is a glitch in the sound - hard to explain, but I'd definitely describe it as a DAC glitch - that classic digital smear/ring sound.

So is there a problem with the DAC or is it simply a problem with the Toslink?

Do I need a SPDIF transceiver module for the original Buffalo?
Is it just a buffering/clocking issue I am experiencing and a transceiver module will fix it?

Currently I'm running the DAC from a single 7v bench supply whilst I test it, and am using an IVY II output stage.
The Toslink module is set to TTL output, and I've tried running it into D1 and the SPDIF inputs.

If I need a transceiver module - will they be in stock again? Or what can I use as an alternative.

Many thanks,
Matt