Yeah, BH lets off a decent pop when firing up the amp, especially with BA's like TF10, R-50, X10. I highly recommend turning the amp on before plugging your earphones in. It's not so bad with full size headphones but certainly rather loud with sensitive IEM, and you get that feeling you shouldn't be doing it. It's fine when powering down.
I have gotten into the habit of unplugging the IEM after each session.