Review on 🔵 DROK Blue~Tooth Board: Portable, 5V-24V Audio Receiver for DIY Home Sound System with Micro USB Port by Daniel Postle

Update July 2020 If you have compared the reviews on this product and you were confused, it is because the seller Drok the product, the photo, the specifications and everything changed while keeping the old product ID. The old product had no relay and no auxiliary input. The new one has. This Bluetooth board has significant DC offset and drift. So when you switch the relay (when a Bluetooth connection is established) there is a loud bang. This is not good. Also, there is no way to adjust the level difference to the volume between the Bt and AUX sources. All in all, a good concept and poor execution. My initial review: The Bluetooth chip is labeled JL AS19AP10757-5C4, but I can't find a datasheet for it online. If anyone finds it, please post a link. So I don't know the official nominal supply voltage range for this IC. However, the power line is regulated by the SE8533, which has an output voltage of 3.3V (the minimum input voltage is 4.3V, but there are reverse polarity protection diodes in series, so you need a total of 5V or more). So I think it's safe to remove and bypass the regulator and run it on a single LiFePO4 cell and possibly safely on a Li-Ion cell. I used it like this with Li-Ion direct (regulator and reverse polarity protection diode bypassed). It's probably unsafe to drive on 5v since they went to the trouble of installing the regulator with USB anyway. Proceed at your own risk. This board has no battery charging circuitry at all. Bluetooth range is pretty good. I cut off this PCB antenna and made a full wave loop antenna to extend the range a bit and improve call quality. The sound quality is okay. Good enough for casual listening. Typical for consumer electronics, it sounds a bit rough and harsh. It's nothing more than a 5G iPod or other quality device with a decent DAC and headphone driver. The audio output has a very low but high-frequency noise that is clearly audible in pianissimo. When I first ordered it, Revain delivered a completely irrelevant product. This is probably an error from their fulfillment center, but I've read that such an error is difficult to fix, so I had to wait a few months to back-order another one. Finally I understood.