Amplifier Card
A Look At Some Of The Trendiest Wireless Toys
Latest-generation wireless audio products such as iPods, iPhones and wireless surround sound products claim to cut the cable while delivering crystal-clear audio. I will take a look at some of the latest gadgets and technologies to see how well they work and in which situations they operate best.
These products fall into 2 categories. The first sort of products already has wireless built in. Second-category products, including some streaming audio products, have optional wireless functionality. Generally they have a slot to add a wireless LAN card. Newest touch-screen iPods and iPhones already have WiFi and Bluetooth built in.
Bluetooth is a relatively low-cost option but has some limitations which are often overlooked.
1) Restricted range
The range of Bluetooth devices is normally only 30 ft. This excludes Bluetooth from multi-room applications.
2) Small data rate – audio compression
Bluetooth offers a maximum reliable data rate of approximately 1 Mbps only. This rate is not large enough to send uncompressed CD-quality audio. Therefore Bluetooth wireless devices apply audio compression. Audio compression will deteriorate the audio quality to some extent. High-quality audio transmission generally does not tolerate this kind of degradation. Therefore Bluetooth is usually not used in high-end audio devices.
3) Signal latency
The audio will experience a delay of no less than 10 ms mostly as a result of the audio compression which is a problem for real-time audio applications but less serious for MP3 players.
4) No multiple headphone support
Bluetooth can not stream to numerous headphones at the same time. This might be a dilemma in cases where numerous people like to listen to the same Bluetooth transmitter.
Another widespread protocol is WiFi which supports uncompressed audio but also has problems simultaneously streaming to multiple receivers. Due to the high availability, WiFi is practical for streaming audio from a PC. On the other hand, WiFi products have fairly high power consumption. Because of this wireless headphones typically do not employ this technology.
While newest-generation wireless speakers and wireless amplifier products employ proprietary digital technologies, entry-level products regularly still depend on FM transmission which is noisy and has high audio distortion and high susceptibility to radio interference.
Modern wireless audio protocols eliminate audio degradation by using digital transmission. These frequently also come with mechanisms including forward error correction to deal with interference from other wireless devices.
Latest-generation wireless amplifiers employ uncompressed audio transmission. New protocols also allow streaming to an infinite number of receivers. This allows whole-house audio distribution.
Some of these protocols support low-latency audio transmission which assures that the audio of all speakers will be in sync in a multi-channel application. Wireless audio transmitter products generally operate at 2.4 GHz or sometimes in the less crowded 5.8 GHz frequency band including Amphony’s wireless audio products.
These wireless amplifiers also differ regarding amplifier output power, standby power consumption and audio quality. A high-quality audio amplifier is crucial for optimum sound quality. Digital Class-D amplifiers offer high power efficiency of at least 80%. They also have low standby power, usually less than 5 Watts. This minimizes heat and keeps them cool during operation. Some digital amplifiers, however, have relatively high harmonic distortion. Picking a low-distortion amplifier is essential. Good-quality wireless amplifiers have audio distortion of less than 0.05%.
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