Fetal Doppler Question

Marisol
For those who have used a home fetal Doppler what is the earliest you can find baby's heart rate? I use it with my son after the 8th week... But wondering any sooner than that? I tried it today just for fun and found a hear rate for less than 5 seconds of 132, I know it could probably be the main artery too but idk lol... 6w1d...