heartbeat

So I've been wondering this for a few weeks, but when I got my first US done I was 8w6d...the tech said that it might be too early to hear the HB but it picked it up loud and clear, and the picture was super clear too. I had my first appt with my OB a week and a half later, and he tried the doppler, warning that we may not be able to hear the HB yet but again, it showed up loud and clear again. My question is, does this seem a bit early to be hearing the HB? I had read that usually doppler isn't able to be heard until 10wks...we were pleasantly surprised.