I ' d love to see that happen . <| sep |> I can ' t decide between Superlux 681 vs 668 . 668 seem to be slightly better overall and 681 seem to have better soundstage . Is this true ? Right now the 681 are about $ 6 cheaper and ship from USA . The 668 are $ 6 more and ship from China and will take close to a month to get here . Thoughts ? I ' m looking for a entry pair and $ 30 and under and figured these were the only options . <| sep |> After a quick google , this videoRKWuBmwomdo appears to show how to do it using comparators . A redstone comparator in subtraction mode front torch up and powered will subtract the signal strength of the highest side input from the signal strength of the rear input minimum 0 signal strength . For example , if the rear input signal strength is 7 , the left side is 2 , and the right side is 4 , then the output will be a signal strength of 3 , because 7 MAX 2 , 4 3 . a b 15 15 a b 15 15 a bSo using comparators do 15 a and let this be cThen again use a comparator to do c b 15 a b and let this be dThen again use a compatator to do 15 d 15 15 a b a b