Bluetooth audio

By Ben Everard. Posted

We’ve looked at a Bluetooth audio receiver before (in issue 18). Then, the board we received couldn’t put out decent audio.

Perhaps it doesn’t make sense to buy a bundled receiver and amplifier board. After all, the subject of audio amplifiers is complex, with options costing from a few pounds to... well, we’re not aware of any upper limit on the amount you can pay for an audio amplifier.

In contrast, a Bluetooth receiver is a much simpler proposition – it receives a digital bitstream and converts this into a low-power analogue stream. Yes, there are quality concerns, but they’re much more limited because the digital nature of Bluetooth audio puts a finite upper limit on quality. Once we’ve got a decent Bluetooth receiver, we can pair it with an amplifier of our choice, whether that’s a new one or feeding the audio into the line-in on an existing system.

We’ve previously used a KRC-86B Bluetooth module, but this seems to be less available and it’s gone up in price significantly since we first experimented with it several years ago.

Now, the most common affordable option is the VHM-314. We bought one from Global Purchase Store on AliExpress for £1.92, including delivery to the UK.

There are two sets of connectors: solderable ones and plug-in ones. For power, there’s a micro USB connector or a solderable ‘BAT’ connector that can take 3.7–5V (a range that includes LiPo batteries, three AA batteries, and USB power sources).

There’s nothing special about the BAT connection (such as charging or power management) – it’s really just a voltage in, and if you’re planning on powering this from a LiPo, you’ll need additional battery management hardware.

Audio out comes via either a 3.5 mm jack or three solderable connectors (LGR). These solderable connectors are surface-mount in that they don’t have any holes. They may fit some form of connector, but we soldered the wires to them. It’s not the easiest soldering job, as it’s slotted between the jack and micro USB connector, but shouldn’t be too hard.

There aren’t any components on the back of the board, so unless you solder into the through-hole battery connections, you can mount this board on a flat surface using the two mounting holes.

Considering the price, this feels impressively well constructed. The 30 mm × 30 mm circuit board is solid, and everything feels firmly attached. It’s certainly a lot more solid than many PCBs we’ve received over the course of putting together this section over the past two years.

READY TO CONNECT

Add power and the light on the unit should start flashing – ours was blue, but some documentation for the unit says it’s red. At this point, it’s ready to pair. Your phone, computer, or other Bluetooth device should pick it up in a scan. You will, however, have to figure out which device it is in the list.

The seller page informed us that it should show up as ‘XY_BT’; the documents linked from the seller page said that it should show up as ‘VHM-314’. However, it actually shows up as XIDADIANZI. It shouldn’t be too difficult to work out which one is the correct device by seeing what appears when you power on the board.

Herein, though, lies our biggest complaint with cheap Bluetooth boards: it’s not usually possible to change the name of them. We’d like this one to identify as ‘Kitchen radio’ or ‘Lounge hi-fi’, but alas, we can’t. It’s possible to change the name that they show up as on your phone, but that doesn’t help other people.

The biggest issue here is that if you have more than one speaker built on the same type of hardware, it’s a recipe for confusion. However, perhaps if we’d ordered more than one, we’d have been lucky and got one that followed the documentation and identified itself as XY_BT or VHM-314.

Beyond this minor annoyance, the board works as expected. It connected and streamed audio and is of a quality we’re happy with. The reception worked at the distances we’d expect it to (with no problems up to about 5-10 m).

The on-board connectors mean that you could easily add Bluetooth audio to an aging stereo without any soldering at all. Just connect up the wires and you’re good to go. With a bit more work, you can build it into your hi-fi equipment a little more neatly.

At just 30 mm x 30 mm, there’s a good chance you’ll be able to mount this inside your existing equipment somewhere. Alternatively, pair this up with an amplifier board of your choice and build your own Bluetooth audio system.

We really like modules like this that do one thing well and are easy to use. You don’t need to program them, you don’t even need to solder onto them, and they can add real value to users.

There are thousands of old music systems that can play great-quality music, but are being thrown out because no one uses cassettes or CDs any more. And while vinyl is undergoing something of a resurgence, it’s tiny compared to the streaming revolution. For just under £2, you can resurrect these systems and get yourself a great hi-fi system, and keep some waste out of landfill.

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