We wrote more or less thoroughly about Bluetooth technology, in particular in audio applications: general information and profiles HSP, HFP and A2DP and the more audiophile aptX HD. Many much more high-profile projects in the field of consumer electronics during this time, flashing with bright marketing, sank into oblivion. And Bluetooth is alive and well! Technology, developing since 1993, is reaching new heights. It's time to see what her latest achievements are.
One of the secrets to the popularity of Bluetooth (and by next year there will be 14 billion devices with this technology in the world is predicted) is backward compatibility. That is, if your smartphone supports, say, Bluetooth 5.0, but your headphones only support Bluetooth 4.2, this means that if they interact, everything will work. True, within the framework of the younger of the two possible versions of Bluetooth. And this cannot but rejoice. After all, often the release of a new version of something completely excluded compatibility with everything that was released before, as if hinting: now it’s time to throw away this working and practically new device. This happens, for example, with many cable connection interfaces.
Bluetooth, which has already succeeded in replacing cables in many ways, has turned out to be much more loyal to users. Moreover, updates occur with commendable regularity. Since our publication, Bluetooth 4.2 has appeared, which differs from Bluetooth 4.1 adopted at the end of 2013 in increased privacy and increased data transfer speed. And for more than three years now, the world has been enjoying Bluetooth 5.0. The range and data transfer speed have increased significantly. Added to this is improved noise immunity. All together made it possible to update audio signal transmission technologies.
Less current, more meters
First of all, we note the development of the Bluetooth Low Energy specification. Starting with the fifth version, it can finally be used by audio devices. This means that your new headphones and the smartphone connected to them can work via Bluetooth longer on a single battery charge. In addition, the Dual Audio function implemented in Bluetooth 5.0 made it possible to play audio on two connected devices simultaneously. For example, listening to the same track together from the same smartphone is much more romantic. Moreover, in principle, you can even transmit two different signals from one gadget to two different devices.
Another thing is whether these possibilities are implemented (and if they are implemented, then how) in each specific case. Indeed, for this, in addition to the readiness of the built-in Bluetooth module, it is necessary to have hardware and software compliance with the remaining systems of the gadget where it is installed.
A separate topic is the documented ability of Bluetooth 5.0 to operate at distances of up to 240 meters. These opportunities are already gradually beginning to be used. True, the developers talk about the documented function as an achievement, possible “after many years of research and repeated tests” - but this will remain on their conscience.
The most important advantage of Bluetooth 5.0 is the ability to use data transfer rates of up to 2 Mbit/s, which is twice as much as Bluetooth 4.2 supports. What real improvements come from this? The simplest answer suggests itself right away: the ability to listen to uncompressed Hi-Res! After all, at a speed of 1 Mbit/s, available with Bluetooth 4.2, the aptX compression standard has already been implemented, ensuring digital audio transmission in almost CD quality.
How to choose a Bluetooth transmitter?
First of all, you must understand why you need it and how you will use it. For example, if you choose a Bluetooth transmitter for your TV (to connect headphones), then you need to find out what connection options are possible specifically on your TV. This is the main thing.
What to look for when choosing:
- To connection interfaces. In most cases, a transmitter with the ability to connect via a regular 3.5 mm Jack or RCA (tulip) is sufficient. The cables are just different. And when ordering, you usually have the opportunity to choose a specific cable, or order both cables. More expensive models are also equipped with optical audio input/output. And if your TV has an optical audio output (Digital Audio Out), then I would advise buying a model that supports this interface. Here is an example of a cheap model that supports only 3.5 mm Jack and RCA (there was no RCA cable included, but it could be selected when ordering):
And the expensive model also has support for an optical audio cable. Well, accordingly, all cables are included.
The transmitter itself has an optical input and output: SPDIF IN TX and SPDIF OUT RX. And on the case there is an SPDIF/AUX switch. Which needs to be set to a certain mode, depending on what cable you use to connect to the sound output source, or to the device to which the sound will be output.
If you take a device with three cables (Optical + RCA + 3.5 mm), then you can definitely choose the right interface to connect to your TV or other device. - Don't buy the cheapest devices. I was personally convinced of this. My transmitter (which is cheap, $3) is terrible at outputting audio to headphones. There is noise and crackling noise during playback. I tried changing the power adapter - it didn't help. While in the opposite direction, it outputs sound from the phone to the speakers without interference. The headphones have been tested on different devices, the problem is not with them. Perhaps I just got a bad one. Also, in cheap models there may be a strong delay in sound transmission (due to the cheap Bluetooth module). And the sound will lag far behind the image on the TV. The cost of these devices greatly affects the quality of the sound and the quality of the device itself as a whole.
- If you need to connect more than one pair of headphones to your TV via a transmitter at the same time, be sure to find out before purchasing whether the model you choose offers this option. In my case, only one headphones can be connected to a simple and cheap transmitter. For an expensive model - two pairs of headphones at the same time. I checked it works. I connected headphones and a speaker at the same time. But the connection process is very complicated. Especially when the instructions are in English and you are too lazy to translate it.
- As for the Bluetooth version, take devices with the latest version. I have both with Bluetooth 5.0. On the headphones, if I'm not mistaken, Bluetooth 4.1. Everything is working. They are compatible with each other.
- There are Bluetooth transmitters with NFC. I don't have one, so I can't check. But in theory, NFC support is needed to make it easier to connect headphones, speakers, phones and other devices, which, of course, also have NFC support. Since the process of connecting headphones and similar devices to the transmitter is still an exercise, the presence of NFC is an excellent solution.
- I've seen transmitters with external antennas. Their characteristics state that the indoor range increases to approximately 30 meters. In normal range, the range is 10 meters. I didn’t have to work with such models, but if you have a large house or apartment, or some special tasks, then this option may be suitable for you. In normal cases, I don’t see the point in overpaying.
- Built-in battery. To be honest, I don’t quite understand why it is needed. For my transmitter, the manufacturer stipulates battery life for 24 hours. But why? It's probably easier to connect power than to think about charging another device. Although, perhaps in some situations the ability to work autonomously may be useful.
Carefully study the technical specifications. It always states what comes with the device, what cables are available, what connection options are available, how many devices can be connected via Bluetooth at the same time, etc. Read the reviews.
conclusions
Interesting and useful devices. You can come up with many options for using them. But the main one is connecting wireless headphones to the TV. Moreover, even in new TV models, which of course are equipped with Bluetooth, for some reason manufacturers limit the connection of headphones.
Everything connects and works, even with a $3 transmitter. But I would not recommend buying such devices. All because of very poor quality and a high probability of receiving a defective device. In addition, the process of connecting such devices is not the simplest and most understandable. On more expensive devices, everything is implemented a little more simply. There are buttons and switches. If only the instructions were in Russian/Ukrainian, that would be great.
When buying a Bluetooth transmitter, be prepared to spend a little time figuring out how to connect and configure everything. Read the instructions on the online store website. Using your phone (camera in Google Translate) you can translate the instructions that come with the kit (if any). In the case of connecting to a TV, there may be some inconvenient moments with switching sound from the TV speakers to headphones and vice versa. Much depends on how the transmitter is connected to the TV and on the TV itself.
- Price: 12.99
- Go to the store
Continuing the topic of converting headphones into a Bluetooth version, the idea was born of retrofitting home appliances, and later a car, with a Bluetooth device that could transmit stereo sound: - from TVs to the resulting headphones, phones for watching TV shows in the “don’t disturb anyone” mode; — from a phone to a car audio system, PC or stereo system. Information about what came out of this is under the cut. For the assigned tasks, a device was needed that combined the functions of a receiver and a transmitter. As a result, the B6 2 in 1 Bluetooth receiver-transmitter was tested.
Technical specifications Bluetooth: V2.1 Protocols: A2DP, AVRCP; Reception/transmission range: 10 meters; Battery: Built-in lithium polymer battery (600mAh); Operating time: up to 8 hours (depending on sound volume); Charging: Micro USB 5V/0.5A; Audio port: 3.5mm; Compatibility: Android, IOS, Bluetooth enabled devices, audio playback devices with 3.5mm ports; Active noise cancellation; Dimensions: 95x 57x 6 mm (L x W x D); Weight: 38g Package Contents Bluetooth Audio Transmitter/Receiver 3.5mm Audio Cable AV Cable USB Charging Cable User Manual
aptX Family: Adaptive, Low Latency and Audiophile HD
And from this place - timpani and fanfare (in HD quality, of course) - Qualcomm aptX HD enters the stage, specially designed to meet the growing demand for high-resolution audio. This advanced codec supports 24-bit quality music over Bluetooth up to 48 kHz. And another achievement is the signal-to-noise ratio, reaching 129 dB, and this is a value that is not available on all modern reference-level DACs.
The developer's website quotes independent tests from the University of Salford: "From an analysis of 24 people taking the test, it was concluded that participants were unable to consistently detect the difference between 24-bit/96kHz audio and 24-bit/48 encoded and decoded audio." kHz aptX HD".
Let's look at an example of implementing aptX HD on the Qualcomm SOC CSR8675 audio chipset. Not only can it handle 24-bit audio pass-through, but it also provides deeper digital signal processing than its predecessors. A reduction in the signal-to-noise ratio is achieved, in particular, through sequential encoding and decoding during transmission/reception. A reduction in distortion is also claimed, especially in the 10–20 kHz range.
The chipset is powered by a programmable 80 MHz RISC processor. The audio signal is processed by the built-in 24-bit Kalimba DSP processor. On board, by the way, there is a stereo 24-bit ADC with a sampling frequency of up to 96 kHz, and a built-in stereo 24-bit DAC realizes a sampling frequency of up to 192 kHz - the parameters are set with a margin.
The developers from Qualcomm did not stop there, offering the aptX Adaptive Audio codec. With low latency in dynamic mode, perfect for gaming headsets, it provides adaptive bitrate, adjusting the data transfer rate for a smooth connection. In its release, Qualcomm talks about aptX Adaptive Audio as a next-generation dynamically configurable audio codec, backwards compatible with aptX and aptX HD.
The company says the codec is designed to "automatically adjust to provide optimal audio quality or latency depending on what content is being played on the device, as well as the external RF environment to ensure reliability." aptX Adaptive can operate at two bitrates: 276 and 420 Kbps. In the second version, thanks to more advanced encoding algorithms, in some parameters like signal-to-noise it even surpasses aptX HD, although not by much.
And another codec from Qualcomm is aptX Low Latency, which uses Bluetooth 5.0 speeds to transmit audio with low latency. The technology provides end-to-end latency for Bluetooth transmission of no more than 32 ms. The latency of standard stereo Bluetooth varies greatly depending on system implementation and buffering, but is typically an order of magnitude higher. And it's noticeable.
In particular, the use of Bluetooth devices to implement wireless headphones to a TV was almost impossible. After all, the recommended delay for synchronizing audio and video in broadcast television is from +40 ms to -60 ms. The best technical solutions (concert and studio monitor systems) should comply with the level of 20–30 ms. aptX Low Latency approaches them, providing new capabilities, in particular for gaming applications. We can no longer notice a delay of 32 ms (or, let’s say, we may not even notice).
What is a Bluetooth transmitter and what is it for?
As a rule, these are compact devices that have a built-in Bluetooth module and various audio inputs/outputs for connecting to different sound sources (TVs, computers, phones) or to devices that are designed to output sound (speakers, speaker systems, stereos, radios, etc.) etc.) . All these devices differ not only in technical characteristics, but also in appearance. Here are some of them:
The main differences between different models of Bluetooth transmitters:
- Supports different connection interfaces. For example, there are transmitters that connect only via a regular 3.5 mm Jack. And there are models in which, in addition to a 3.5 mm jack, there is also an RCA (tulip) and an optical audio input/output.
- The presence or absence of a built-in battery.
- Bluetooth versions.
- Possibility of connecting several Bluetooth headphones or speakers.
- The quality of the Bluetooth module, the presence of different control interfaces, build quality, cables, etc.
If I understand correctly (I may be wrong, since it is unrealistic to check all devices), then all Bluetooth transmitters on the market can operate in receive and transmit mode (2 in 1). Since even my cheapest adapter can both receive sound via Bluetooth and transmit it to the same speaker system, and transmit sound via Bluetooth (from a TV, PC) to headphones or another device. Typically these modes are called TX Mode and RX Mode .
- TX – transmitter mode. When a Bluetooth transmitter receives sound from the same TV through a specific interface (cable) and transmits it to headphones via Bluetooth. These devices are most often used in this operating mode.
- RX – receiver mode. When we connect regular speakers, a stereo system, a car radio (via AUX), or another device for sound output to the transmitter via cable. Then, from your phone, tablet, laptop or other device, connect to the transmitter via Bluetooth and stream music. It turns out that we will add Bluetooth support for regular speakers.
The picture below shows the operation of two modes:
Even my cheapest transmitter works in two modes without problems (almost without problems :)). Receive and transmit sound via Bluetooth. Only the way to switch between modes on different transmitters is very different.
If the expensive one has a separate TX/RX switch, then the cheap one has no buttons at all. And changing the mode occurs by connecting, disconnecting and reconnecting the device to the power source. In receiver mode the indicator flashes blue, and in transmitter mode it flashes red. Without instructions (which, by the way, were not included in the kit), it’s impossible to guess. It’s good that at least it’s written about this in the product description on Ali.
Use case #1
This example shows operation in transmitter (TX) mode. The TV does not have Bluetooth (or there is Bluetooth, but the headphones do not connect), and we need to connect wireless headphones. We connect the transmitter to the TV using an audio cable. If your TV has a 3.5 mm headphone output, use it. Mine, for example, does not have a 3.5 mm jack. Therefore, I connect via optical audio output. You can also use RAC (tulip). Even old TVs have it. It is very important to take this into account when choosing this device. You also need to connect power to the transmitter. I connect it to the USB port on the TV. If there is no USB, you can use any adapter that you use to charge your phone.
After turning on the power of the transmitter, you need to connect Bluetooth headphones to it. Usually, it is enough to switch the headphones to connection mode. The connection method may vary slightly depending on your transmitter and headphones. Once connected, the sound goes to the headphones. The more expensive model can connect two pairs of headphones at once. When connected to a TV via an optical audio output, sound is also simultaneously played from the TV's speakers. But you can simply turn it off, or turn it off on the TV. Then the sound will only be played through the headphones. There is a slight delay between the sound coming from the TV speakers and the sound coming from the headphones through the transmitter.
Use case #2
This example shows operation in receiver (RX) mode. There is a regular speaker system without Bluetooth. But we want to stream music from our phone or tablet to it. Or even from a laptop or PC, but we do not have the opportunity (or desire) to connect the speakers to the computer via cable. We take the Bluetooth transmitter and connect it to the speakers. Here, in the same way, you can use either a 3.5 mm Jack or a RAC or optical audio cable. Depending on what connection connectors are on your transmitter and speakers. You also need to connect power to the transmitter. Power can be taken from the USB port of any device, or through an adapter.
Switch the transmitter to receiver mode (RX). In this mode, it is discoverable on all devices (phones, laptops). We turn on Bluetooth, for example, on the phone, and connect to the transmitter (its name should be written in the instructions). The phone or other device recognizes it as headphones and outputs sound. And the transmitter, in turn, transmits sound to the speakers via cable.
Video and MIDI
Thus, the capabilities of Bluetooth 5.0 have become the property of lovers of high-quality audio to an even greater extent than before. And this does not mean that the development of Bluetooth does not penetrate into other areas of multimedia entertainment.
If you look at the existing specifications section on the website of the Bluetooth SIG organization, which develops the technology, then, in addition to the advanced audio distribution profile A2DP version 1.3.2, you can find the A/V remote control profile - AVRCP, the general audio/video distribution profile GAVDP (existing, by the way, since 2012), HID, user interface device profile and other promising features.
We should also pay attention to the BLE MIDI technology (also called Bluetooth SMART), which is distributed to the MIDI community, which includes not only professional musicians. We are talking about playing MIDI recordings or MIDI sequences generated by interfaces (even plant growth) via Bluetooth. These Bluetooth technologies create new freedom for creativity and new experiences. What Bluetooth will give us next in its development will become known very soon. The release of a new version is expected in the near future.
