Audible differences are very similar to the conclusions written by CKKeung for the battle between OP20 and OP17.
Quote
"The effect of OP17 was like cleaning a glass window thoroughly, making it spotless & dustless.
But the effect of OP20 seemed like to have removed the glass window completely. The audiences were then inside the concert venue and the images there seemed to be real/touchable!"
End Quote
I am looking forward to using a full stack dCS Vivaldi system to compare Mutec Ref10 SE-120 to Cybershaft OP21A.