Tonight I finally found the original Volumite module, and it does have the old/original controller chip on it ;/ (sorry Brian for making you ship out a new chip)
In addition I was also able to find one of the old Soundblaster Live! cards for my computer, which has a proper spdif output on it, which allows me to just bypass the toslink module entirely. I've verified that the spdif signal from the sound card works (with my other DAC).

I removed the replacement controller chip from the buffalo itself and connected the volumite up according to the documentation (making sure to get the correct order for SCL and SDA) and used one of the the LCDPS outputs V+ outputs to power it (but using the ground from the I2C header)

Alas; no change at all, the automute led is still lit, and the lock led is not. I still get the same almost inaudible sine wave sound on the dac outputs.
I only tried feeding the spdif signal from the sound card into the spdif input with the spdif switch set to on (not into D1), can someone verify this is correct?

I'm not 100% sure if the spdif output from a consumer device would be "normal" or "TTL", from what I've read a consumer device should be "normal" output, which is 0.5 Vpp right?

avr300: you mentioned a scope, I know there are some fairly low cost options for scopes out there now, what specs would I need for this? Could I just buy a cheap usb scope of some kind on ebay?
I had access and used some scopes back when I was at university and took some introductory electronics classes, so I do have some (very limited) experience with using them.

If the spdif switch or the comperator circuit is broken could I bypass that section entirely by doing the following? :
- Unsolder the switch (so that it is open)
- Feed TTL spdif from the toslink module into D1 (the toslink module does ouput TTL level spdif right?)

I think maybe unless anyone else has any must-try ideas I'm probably just going to move on from this soon, and perhaps try to find some way to reuse the other components.
I do wish I could find the problem, even if it is not fixable, that way I could at least learn from it:/

Hmm ok I changed it as you suggested, does not seem like it made any difference, I tried with both the toslink module and direct spdif.
I have all the dip switches set to neutral, except for the SPDIF switch which is set to ON, I used the SPDIF and G inputs in the buffalo.

No matter what I do I just can't get a lock. I did also double checked the lock led by measuring voltage, just to make sure the led is not dead or something.
Is there some way I can verify that the controller chip is working at all? I mean, the automute led is on and I assume that is normal when there is no signal.. is there something I can do to test that things are "ok" beyond that?

I'm not sure if it's possible to measure the spdif signal with a normal multimeter, but when I measure it I get ~1.3VDC from the toslink module and ~1.2VDC from my direct spdif source.

For a cheap scope; what you guys think of the Hantek DSO-2090?
http://www.hantek.com.cn...produce_list.asp?unid=62
It's only ~$150 on ebay so I miight be able to justify getting it;P