Hiflight's kit came with some simple instructions that are especially designed for those that have not changed away from the original opamps within the D12. It is then a simple case of removing the silver and red painted buffer and output opamps and then plugging in the same colours from Hiflight's kit. The Hiflight kit has one of the edges of each chip painted rather than the entire chip as in the case of the original iBasso opamps.
I am a bit of a novice when it comes to opamp rolling except that I have tried all of the combos of the standard supplied option opamps as well as the extra opamp kit which is sold by iBasso. I have even tried combinations that must be wrong as they result in no sound. Luckily I havent managed to destroy anything yet. It is normally that I have a chip that is meant for buffer rather than output, or vice versa.
My current listening is with the chips that Hiflight refers to as suited to rock and roll. I am listening to an Album titled Down The Way by Angus and Julia Stone. It is a ripper if you like clean sounding folk. Check it out.
The first thought that comes to mind when listening to this combination of chips is thick. Thick as in a tube type sound but still sharp and without softened edges. The sound is also fuller from a sound stage too. I notice that male voices and upper bass may be a little more noticeable too. Kick drums have a little deeper sound to them with a heavier skin sound. The bass could be why voices seem to have greater timbre and resonance to them also. Contrasting this strings of a guitar also sound more crisp. I am not sure if treble is more pronounced or if the entire amp just sounds more powerful. Probably the latter but I am not an expert by any means.
What I can say though is that this is a great combination and makes the already great iBasso D12 that much better again. Certainly worth the $65 landed price. Many thanks to Hiflight.