Sound input on PowerMac 7500

[Will]

Is there an issue with sound inputs on a 7500 under YDL?

I'm running YDL 2.3. dmasound_pmac is installed and sound output from 
sox, KDE and Gnome all work fine. However I can't get anything from the 
built in line inputs.

Under KDE the CD player and mixer work fine.

The Gnome CD player, mixer and sound recorder all work and can be used 
to record from the CD.

Trying to record from the line inputs using sox doesn't give any 
errors, but the resulting files are empty.

I also tried the Old World kernel 2.4.19-ben0 in case that is required 
to support the older sound hardware. No luck!

I'd appreciate any information/tips anyone has about this.

Ian