PAM8403 filter

[lmadden1]

I have been playing with the frequency generator and the PAM8403. Do you add any low pass filtering to the PAM8403 Class D before feeding the ultrasonic transducer? Also, like other contributors I am having difficulty finding a 25kHz transducer, do you believe 40kHz will work? Any changes to the design as a result? thanks /liam

[T-vK]

Personally, I didn't get very good results with a 40khz transducer. I haven't received my 25khz transducers yet so I can't really compare the two. All I can say is that with a 3W amplifier at max volume I get a little less than 1 meter of range. I can't say if my transducer is already running at more than 100db (which could cause permanent hearing loss btw) or if it's actually only running at 60db and I just need a bigger amplifier.

You might wanna read through this issue: https://github.com/y-x-c/wearable-microphone-jamming/issues/6

I'm also currently working on a simpler design that doesn't require an external signal generator. You can find the wiring diagram, parts list and code here: https://github.com/T-vK/alexa-jammer#how-to-use-the-mic-jammer