Ah, yes Mike, you spotted that - I left out the details for brevity [smiley=grin.gif] but there are two types of configurations used:
- series fixed R & LDR shunt or
- LDR for both series & shunt
Diagram & short discussion here:
http://www.audiocircle.com/circles/index.php?topic=59802.0
There is some discussion that the second config sounds best & this would be a question that could also be addressed with the uC controlled matching of LDRs.
In the absence of a uC, the series LDRs would need to be matched between channels & the shunt LDRs would also have to be matched between channels but a quad match would not be required just two pairs that matched.
This config is of course much more difficult & expensive to realise without uC control over dynamic matching & rules out any more channels than 2 being used.