I’m wondering if anyone might be able to answer what is hopefully a relatively simple question please?
I have a project (a fully functional BB8 droid) which is using (amongst other things) an Arduino Uno with a Geeetech MP3 shield, and a cheap 100w amp to power a speaker.
Reading up on the MP3 shield there are warnings floating around about using it to power an ‘external’ amplifier, because of the risk of a ground loop. My Project only uses one power source (12v battery) to power everything, including the Arduino (via a voltage regulator set to 9v) and amplifier (which uses 12v), so do I still need to be concerned about amplifier protection? If so, what might my options be please?
Thank you for any help you can provide
Edit, typical noob move, posted in the wrong forum. Sorry, I’ve reported my post to admin for moving/removal. Doh!
Sometimes those audio shields with headphone outputs use a virtual ground at the headphone output. That’s done so you can get AC out (positive and negative voltage swing) relative to the virtual ground with a single-ended power supply.*
Connecting/shorting the virtual ground to the actual ground at the amplifier can cause “problems”. If the manufacturer of the MP3 shield doesn’t tell you how to deal with a virtual ground, check the datasheet for the chip.
And, any clicks, pops, hum/buzz, loud test-tones, or loud distorted voice/music at 100W can fry most speakers… It’s kind-of “dangerous” to play-around with high power until everything is tested-out and stable. (A 100 W speaker is designed for handle occasional 100W peaks at around 10W average.)
and amplifier (which uses 12v),
You can’t get 100W from 12V. 100W into 4-Ohms requires 20V RMS, which is 28V peak and 56V peak-to-peak. Double that with an 8-Ohm speaker. That requires a power supply slightly higher than 56V for a normal single-ended output or slightly-more than 28V with a bridge output. (High-power car amplifiers have an internal DC-DC voltage booster, to get high power from 12V.)
DC blocking capacitors can will allow positive & negative voltage swing relative to the true ground, but it takes relatively large-bulky capacitors to pass the bass frequencies into headphones. (I don’t see a pair of output capacitors on your board.)
