Using my 4.A I'm getting quite a bit of hiss/background noise. Playing music or not it's kind of annoying. High gain there's less noise but I still notice it. T50rps are fine.
Also I noticed some people listening with iems at 160-170? I'm finding with the 4.A 115 is pretty loud (low gain).
I'm trying to identify if it's due to a discrepancy in a selected batch of product.