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Jan 31, 2017, 06:49 PM
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Stock bluetooth board

So the bluetooth board caused a power supply noise problem when it used the TDA1517 as an amplifier. Must figure out how to defeat power supply noise, 1 of these days. Decided to discard the entire TDA1517 board & just use the bluetooth board with the old speakers because it would be the lightest.

The bluetooth board had some kind of series capacitor network feeding the amplifiers.

1uF + 20k + 100nF + 20k

Replaced it with just a


to try to make it louder. It now seemed just as loud as the TDA1517. The chinese datasheet showed a 58nF + 30k.

The BK3254 had no datasheet, but if holding down the power button to turn it on was annoying, it could be powered directly by applying 3.3V to pin 16. Unfortunately, it automatically reset this way so some other voltage was missing, perhaps 4.2V on pin 17. Never could find a 3.3V source on the board, so perhaps the chip implemented its own regulator & power button control.

Also, cable management nightmares proved a speaker is best powered by its own battery instead of the vehicle power.

It's probably best to use a bluetooth speaker as is, except for replacing the speakers & enclosure to make it lighter & louder.

In other news, discovered phones probably aren't cracking when the vehicles roll over but when they jump off curbs. When the vehicles always carried a shirt, the phones had cushioning & didn't crack. With a severe winter leaving the vehicles devoid of a shirt for many months, phones started cracking like crazy. They're also self destructing to get cheaper & thinner.
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