Wireless transmission of audio signal to speakers. Sound accompaniment - without wires. Assembling a device for wireless audio transmission
It would be categorically incorrect to say that various cables are a nuisance to the typical audiophile. Moreover, sometimes this is his only outlet in terms of experiments on an already built system, the opportunity to at least somehow modify its sound. And it doesn’t even have to be improved, but simply given a certain shade. But, an audiophile does not exist in a vacuum (because a vacuum does not conduct sound), including a social one, he is often surrounded by his wife, children, animals... And it is precisely for them that numerous “wires” are quite annoying, they can trip over them, because They are inconvenient to clean and can even be chewed on!
It’s good when the installation begins with renovation or even construction, all switching can be removed into the walls, floor, ceiling, but what to do when the equipment is installed in a ready-made room? And that's only half the problem. A stationary system is certainly good, but when was the last time you thoughtfully listened to an entire album without leaving your chair? Much more often you want to listen to something in the kitchen, bedroom, veranda, etc., right here and now. And the fewer wires, the more mobile the equipment becomes and the easier its switching. So what opportunities does the wireless audio market currently offer?
If you do not take into account ancient infrared and radio headphones, then historically the first wireless standard became Bluetooth, which is already more than 20 years old. Originally intended to replace wired interface RS-232, it later became used for voice transmission in telephony, and now for music. The main advantage of Bluetooth is its low energy consumption, which is why it is used in the vast majority of smartphones and portable speakers. Moreover: it can even be used to connect headphones (for example), while the battery charge lasts for several hours. The disadvantages of the standard are also well known: short distance reception and transmission (although in recent versions it has increased significantly), poor permeability (most often within line of sight) and relatively low speed. The last drawback is probably the most relevant in relation to audio equipment, however, thanks to aptX technology, it has become possible to provide a level of signal quality comparable to a CD. This principle works, for example, portable devices Arcam (miniBlink, rBlink, irDAC-II), Cambridge Audio speakers, Monitor Audio ASB-10 soundbar, etc.
What about Wi-Fi? After all, now almost every apartment or house has a wireless network. This is true, but since the network is designed for data transmission, this transmission is carried out using the packet method, as opposed to the more familiar and suitable for streaming music. Despite the general digital nature, music, unlike data, must first be packaged in these same packages and then transferred, without spending too much time on it. Plus provide a friendly interface with the user, and not some command line, full of hidden hopelessness.
As a result, some companies began developing a software shell for transmitting sound over Wi-Fi. Perhaps the most famous implementation options are Sonos, HEOS, MusicCast, Bluesound. There are two disadvantages to this approach. Firstly, these protocols can be used almost exclusively by devices from one manufacturer and it is almost impossible to create a mixed system. Secondly, software implementation, for one reason or another, may impose restrictions on the transmission and reception speed: the same notorious Sonos has not yet gone beyond CD quality. The situation is much better for standards that are not directly tied to hardware manufacturers - for example, AirPlay or Play-Fi. The first one is moving forward by Apple, the second is DTS, both can be licensed for use by third-party companies, which is what Hegel (HD30) or Arcam (rPlay) use in the design of their devices.
However, if you have the proper skill (or rather, specialists who have it), you can transfer musical information using classic Wi-Fi, as for example done in network players Burmester and Cambridge Audio.
Developers from the German company ELAC went even further, using proprietary KleerNet wireless technology from Microchip. This solution allowed them to provide audio transmission with a resolution of up to 24 bits / 96 kHz in the Air-X series speaker systems.
It is curious that all of the above options are designed for stereo broadcasting, but if you need to build a full-fledged wireless home theater, then you cannot do without professional solutions - for example, AVB (Audio Video Bridge), where components on the network not only exchange data, but are also synchronized. Until recently, this standard was used only in recording studios, but thanks to the efforts of the German company Ascendo Immersive Audio, this technology can now be used at home.
Well, since we are talking about cinema, we must not forget one of its main components - a subwoofer, which, it turns out, can also be wireless. For example, the British company, a recognized world leader in the development and production of this type of speakers, has two options in its assortment wireless connection: Arrow – for lower series models and Longbow – for uncompromising installations.
How do you transmit sound from sound card your PC to a speaker amplifier? Probably in the traditional way - using cables. We propose to get rid of wires and organize wireless sound transmission via a laser beam over a distance of up to several meters.
The device circuit is easy to assemble and does not require deep knowledge in radio electronics.
Principle of operation
From a low-power sound source (PC, mobile phone), an audio signal is sent to the primary winding of the transformer, comes out of the secondary winding, is amplified by the battery and goes to the LED / laser diode. The light beam is received by the solar module, which is connected to the amplifier.
Thus, sound transmission is carried out wirelessly over distances of up to several meters.
Manufacturing
You can use any network transformer with a power of no more than 20 W, containing a secondary winding of 6 or 12 V, or you can wind it yourself (primary winding - 15 turns of 0.8 mm wire, secondary winding - 10 turns of 0.8 mm wire).
The battery is used Li – Ion (lithium – ion) from a mobile phone. Instead, you can use a stabilized power supply of 3.5 - 4 V, with a current of no more than 1 A.
The LED used is a regular one. It can be replaced with a laser (will significantly increase the transmission distance), which will need to be connected through a 5 Ohm, 0.5 W resistor. The light beam source can also be supplemented with optics from DVD drive, thereby concentrating the light beam and increasing the transmission distance.
Solar module parameters: max. voltage 14 V., with a maximum current of 100 mA. The module can be replaced with any other photodetector.
We assemble the device according to the diagram and the wireless audio transmitter is ready.
The quality of the transmitted signal is quite good, no sound distortion is observed.
Based on materials from the site: radioskot.ru
We transmit sound wirelessly and without a radio channel. I'll be testing wireless transmission for a week. sound signal. The method of transmitting sound over short distances (up to 15 meters) is quite simple if you use a laser emitter. Today I want to tell you specifically about transmitting sound over distances using a laser beam. To assemble the structure we need very little - an audio signal source ( music Center or mobile phone), a ferrite ring, a resistor from 15 to 47 ohms and a battery from a mobile phone.
To receive an audio signal, we need a photodiode and a low-frequency amplifier. Two windings need to be wound on a ferrite ring, the primary winding has 20 turns of wire with a diameter of 0.5 millimeters, the secondary winding has 30 turns of the same wire.
The primary winding must be directly connected to the audio signal output. We connect the minus of the battery to one of the ends of the secondary winding, and connect the plus of the battery directly to the plus of the laser diode.
We connect the second end of the secondary winding through a 15-47 ohm resistor to the negative of the laser diode (any laser diode will do, for example, from a CD or DVD player), it is advisable to use a laser pointer, which can be purchased in a store.
The photodiode, which serves as an audio signal receiver, is directly connected to the input of the power amplifier. Next, turn on the music and direct the beam to the photodetector and voila! The sound flows through the laser beam to the receiver and the power amplifier amplifies weak signal and in the end we get fairly high-quality sound. Instead of a laser, you can also use an ordinary LED, but in this case the transmission range of the sound signal will be no more than 30 centimeters; it is advisable to use white or ultraviolet LEDs from lighters. When using a laser pointer, it is possible to transmit an audio signal over a distance of up to 15 meters, and note that the sound quality is quite good.
The transmitted sound is quite powerful at a distance of 7 meters, the amplifier at full volume delivered 80 percent of its power to the load. Such a device has found very wide application in science and technology; laser microphones for espionage are based on precisely such a transmitter and receiver.
This device is an excellent accessory for a computer, imagine music is playing on the computer and the power amplifier is not connected by cable to the computer, friends will be shocked when they see this miracle, you must agree that it is a truly wonderful device, this way you can also transmit a conversation, you just need to apply a signal to the input of the device from microphone (with preamplifier) and in the end we get wireless phone or a walkie-talkie, or an excellent bug for short distances, later I’ll tell you how to transmit sound over longer distances in the same way.
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The gun's master oscillator is set to a frequency of 60-65 kHz; for 400 volts, the secondary winding contains 80 turns of wire 0.2 -0.6 mm. The winding is wound in 2 layers of 40 turns. Several layers of adhesive tape or electrical tape can be used as interlayer insulation.Save and read later - 
Wireless audio transmission technologies are becoming increasingly popular in the Hi-Fi market, and they are being actively adopted by companies specializing in the production of audio equipment.
Conventionally, all existing methods of signal transmission between audio devices can be divided into three classes. The first are technologies developed and patented by the Hi-Fi companies themselves. They imply the presence in the playback device (for example, an active speaker system) of a signal receiver, as well as an external transmitter (supplied or purchased separately), which must be connected to the signal source. Examples of such systems include Dynaudio and Audio Pro speakers, as well as Arcam docking stations.
Another class of Hi-Fi equipment involves the use of Wi-Fi transmission, for which the playback equipment must be connected to the existing wireless network(with assignment of an IP address). After this, it will be possible to stream audio from any device (PC or portable gadget) running on the same “grid”. As one of the varieties of this type of connection, we can mention AirPlay, which provides a direct connection between the receiver and the transmitter, provided that iTunes software player is used to listen to music.
The third type wireless communication in audio, which will be the subject of our more detailed consideration, is Bluetooth. Appearing on the market more than 10 years ago, initially this technology did not provide very high quality sound, and was used to create wireless headsets For mobile phones. However, Bluetooth 2.0, which has a higher data transfer rate and better communication quality, also had very serious potential for improving the quality of transmitted sound. And the latest Bluetooth 4.0 format, while maintaining all the advantages of the “second” version, is even more economical, which is necessary to extend the operating time of portable devices.
We encode the sound
There is a so-called Bluetooth Profile, which describes the functionality of this wireless connection. In particular, the A2DP (Advanced Audio Distribution Profile) profile determines how well the sound will be transmitted (mono or stereo) when using Bluetooth.
A2DP, on the other hand, supports several codecs that encrypt the original digital audio signal for transmission over Bluetooth. All devices equipped with Bluetooth support so-called basic codecs (SBC), but may also support additional codecs such as Apt-X, AAC, MP3, etc. They provide best quality sound than SBC, and Apt-X is the most advanced audio codec today.
The basic SBC codec uses a limitation of the frequency range of the transmitted signal with a sharp drop in frequency response above 14 kHz, so it is not suitable for high-quality music listening. MP3 and AAC codecs are built on the basis of unprofitable “smart” data compression with information losses, due to which the sound quality is also poor getting worse.
The Apt-X codec uses ADPCM audio processing technology, which is lossless data compression, supporting 16 and 24-bit processing, and width dynamic range up to 120 dB. In fact, the differences between it and MP3/AAC codecs are the same as between audio files compressed in MP3/WMA and FLAC/WAV. At the same time, the Apt-X codec can transmit audio encoded in MP3 and AAC without additional processing, without compromising its quality.
Processing of the received audio signal begins with a latency of less than 1.9 ms, while the latency of MP3 and AAC is more than 100 ms. The basic SBC codec also has low latency, but it is achieved through the use of buffer memory, which imposes certain restrictions on the structure of transmitted data packets, and ultimately leads to deterioration in sound quality. Apt-X does not require data buffering. In addition, the Apt-X codec has auto-synchronization between the receiver (encoder) and the transmitter (encoder), which allows it to be restored in less than 3 ms if the connection is lost.
The Apt-X codec can be used to transmit audio signals in hi-fi equipment, although it requires more processing power from the audio processor (32 MIPS for Apt-X versus 12 MIPS for SBC). Therefore, if you are interested in high-quality wireless audio transmission in your home system specifically via Bluetooth, make sure that both the transmitter (for example, a smartphone) and the receiver built into the active speakers or audio system support this technology.
However, as always in similar systems communication, the principle of backward compatibility is laid down here. That is, if a transmitting device that supports, for example, the Apt-X codec tries to communicate with a receiver that does not support it, then it will switch to the basic SBC codec, of course, with a deterioration in sound quality.
Basic parameters of the A2DP Apt-X codec:
- Compression ratio: 4:1
- Audio format: 16-bit, 44.1 kHz (corresponding to CD-Audio)
- Bitrate: up to 352 kb/s (SBC – 320 kb/s)
- Frequency range: 10 Hz – 22 kHz (SBC – 20 Hz – 17 kHz)
- Transmission latency: less than 1.89 ms at 48 kHz
- Dynamic range: 16 bit, more than 92 dB
- Noise and distortion: - 68.8 dB.
Prepared based on materials from the portal "www.hifinews.ru", April 2013.www.hifinews.ru
Creates a magical audio system for you.
Connection to your traditional active speaker systems or to external amplifiers, music centers.
Connecting the AudioCast M5 to powered speakers will transform your traditional audio system into a wireless one, allowing you to control your wireless audio system in a much more convenient way.
Easy setup
AudioCast requires no technical or wireless knowledge. Connect active Acustic systems in the room where you want the music to play, connect to home Wi-Fi network using the AudioCast application, which provides simple on-screen and voice prompts. With a few steps, you'll be playing music in minutes.
Access to music resources.
Streaming audio
With the Play iEAST app, you can stream music from:
- Smartphone local memory;
- USB flash drives or USB hard drive;
- Home server (NAS); Analog audio input from the source to the StreamAmp AM160 and at the same time transmit music to other rooms (zones) while controlling multiroom;
- Popular Internet music servers and radio stations, such as Spotify, Qobuz, Tidal, Pandora, vTuner, Napster, TuneIn, iHeartRadio, etc. (note: online availability of services varies by region; for example, the world’s popular free Spotify server, although it’s not difficult to register and use the server by googling it on the Internet)
Audio system control.
Control your music using your smartphone and tablet
The free iEAST Play app for Android, iPhone, iPad and Mac allows you to control your audio system comfortably from the palm of your hand. Download Play app iEAST version of iOS OS from App Store And Android versions from Google Play.
Multiroom management
- Play the same song in every room in perfect sync. If you have several speakers connected to different StreamAmp AM160 amplifiers, or one of ours, you can easily group the devices and listen to the same music in all rooms simultaneously.
- Stream (play) different songs in each room at the same time. You can tune into a radio station in the kitchen, listen to a song from an online music service in the bedroom, and listen to music from your phone in the living room, all at the same time.
Other great features.
Sleep Timer
You can set the date and time in the app, and customize automatic shutdown music in case you fall asleep or if you need to listen to music for a certain period of time.
Alarm
Set an alarm to wake up to your favorite music or radio station, in one room or in all rooms.
Software Update.
New features and music servers are automatically updated
The iEAST Play app will automatically notify you if there is new firmware with new features and music services. You can freely update the firmware to latest version. You only need to press one button, the system will update, and you will see prompts on the screen and hear voice prompts.
