You do realise its the caffeine you crash off not the 1.3dmaa in jack, I take roughly 8-10x's the dose of 1.3dmaa thats in jack3d along with ephedrine and on occassion some other goodies and 0 crash, reason being there is no caffeine
Just buy bulk 1.3dmaa its far cheaper then buying jack and far more effective then the nominal amoints they put into their supp (soon to be none because its banned in most countrys worldwide now), thats why they use the caffeine, to cut costs