Smaller cog now chains loud?

Assuming track ends or rear facing dropouts then have you checked the alignment of the rear wheel? Look at your rear cog and chainring directly from above ... are the teeth fully centered between the chain links? If your rear wheel is aligned even slightly off, it can cause your cog / chainring teeth to pull diagonally against the chain, resulting in noise at the point where the teeth come into contact with the edges of the chain.

Going to get flamed to fuckery here, but I actually find that TWO tugnuts are great for micro-adjustments to wheel alignment.

i have some of those chain tugs for forward facing d/o and they definately help having one each side for just this problem

the DA sprockets are wider a fraction than most so i'd check the alignment of the wheel.