Pregnancy Doppler Help...?

All I know is that I got the angelsounds doppler for $30 and was able to hear the heartbeat at 10 weeks (which is when i got it, so I might have been able to hear it even earlier). It's awesome, I'm so glad I got it. It even comes with a cord so you can record the heartbeat onto your computer or hook it up to speakers so you can blast it throughout your house and freak your pets out. Priceless.