How does Dave get the rythem guitar part in Dogs and Sheep? That real crunched overdrive sound.

Wondered the same thing myself. I think by that time he was using Mesa Boogie Amp with a Tele. Or maybe the Mesa came later on "The Wall". Bet there's some kinda overdrive pedal as well. Definitly not a Klon Centaur.

Some people tell me it is the Big Muff, but I don't think so.

"Even a stoped clock tells the right time twice a day"

I understand that he did use a big muff, which he has also used on Comfortably numb. The big muff was modified by Cornish so that the signal to noise ratio was improved to give a lower noise output. Apparently back then the Big Muff had a lot of background noise.

I am thinking it has to be his Hiwatt's totally cranked. I have tried Fuzzfaces, Big Muffs,proco Rats, and the chandler tube driver. But none of the pedals quite nail the tone!