Amphony 1000 User Manual
Frequently Asked Questions
2.4 GHz DIGITAL Wireless Headphones, Model 1000
Q: What is the difference between the Amphony 2.4 GHz Digital Wireless headphones and
current 900 MHz wireless headphones ?
A: The main difference is how the audio signal travels from the transmitter to your headphones.
Almost all of the current wireless systems on the market use a method called FM (Frequency
modulation) which is very similar to the operation of your FM radio. The major drawback ist that this
type of modulation is ‘analog’ which is the reason for the poor performance of 900 MHz analog
headphones.
If you listen carefully to a CD over 900 MHz analog wireless headphones, you will notice significant
noise/static, low signal dynamics and low channel separation. Also, the signal quality will vary when
you move around the room (the noise will increase locally and also the further you move away from
the transmitter).
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Our headphones use something which is called ‚digital' modulation. The same way music is
recorded on a CD using 1's and 0's, it is transmitted as 1's and 0's to the headphones. The result of
this technology is that there is no audio quality degradation during transmission, i.e. you will hear
the exact same audio quality as you would with corded headphones.
Because of this digital technology, these headphones are very suitable for high-quality audio, such
as music coming from a CD, DVD, digital satellite receiver etc.
Q: Can these digital headphones also be used for my analog television or receiver ?
A: Yes. The transmitter has an analog audio interface which connects to the standard line output of
your analog television or receiver. The analog audio is converted to a digital signal inside the
transmitter and then transmitted digitally to your headphones.
Please note that even though there is no audio degradation during transmission to your headphones, you will hear noise if the analog input signal is already noisy. This is often the case for
analog audio sources.
Q: Is the technology used in these headphones similar to Bluetooth or MP3 ?
A: Even though both our headphones and Bluetooth / MP3 use digital audio, there is a fundamental
difference between Bluetooth and how audio is transmitted to our headphones. Bluetooth is only
able to transmit audio data at very low data rates reliably (typically up to 200 kbps). Therefore, only
compressed audio can be transmitted via Bluetooth. A commonly used technique to compress
audio data is MP3. Our headphones, however, do not compress the audio and transmit the full bit
rate. As a result, the audio quality is not degraded such as with MP3. Also, the audio latency (audio
delay) of MP3 compressed audio is fairly high and thus not suitable for television or video
applications. Since our headphones do not compress the audio and since only a minimum of data
buffering is used, the audio delay is minimal.
© 2004 Amphony 1
Q: What is Forward Error Correction and why is it used in these headphones ?
A: Occasionally, there may be some data which is corrupted during transmission. This may be the
case when there is interference, such as other transmitters, electrical sparks or if you move around
and the signal is temporarily lost. Forward Error Correction as it is used in our headphones can in
most cases repair the data which is received to guarantee 100% correct data reception and
therefore 100% correct audio reception.
This technology is in part responsible for the high robustness of the transmission. With 900 Mhz
analog headphones you may have noticed ‘clicks’ or ‘pops’ during sparks which often occur when
switching on appliances.
Q: What exactly is a RangeBooster transmitter ?
A: A RangeBooster transmitter is a secondary transmitter which can be used to extend the opera-
ting range of the 2.4 GHz Digital wireless headphones. This is useful if you want to listen to your
headphones in areas where the signal may be blocked by walls or other obstacles. Also, the use of
RangeBooster transmitters is recommended in areas where there may be strong interference from
other transmitters, microwave ovens etc.
Please do not use a 5.8 GHz RangeBooster since it will
not work with your 2.4 GHz headphones.
The RangeBooster transmitter can be placed in an area where signal reception from the main
transmitter is not possible or difficult. It is possible to use multiple RangeBooster transmitters. It is
necessary though to have a cable connection, preferably a coaxial cable connection, between the
location of the main transmitter and any RangeBooster transmitter. The audio will be transmitted
from the main transmitter to any RangeBooster transmitter via cable digitally, i.e. without any audio
degradation.
Please do not use a 5.8 GHz RangeBooster since it will not work with your 2.4 GHz
headphones.
Q: What are the benefits of transmitting the full data rate without using audio compression ?
A: Since our transmitter transmits a data rate of over 3 Mbps (3 million bits per second), the audio
can be transmitted without audio compression. Also, forward error correction can be used. The
reason that other systems use audio compression is to reduce the extremely high data rate of a
pure (uncompressed) audio signal in order to either be able to store that signal or transmit that
signal more easily.
The biggest drawback of using audio compression is that the quality of the audio signal is reduced,
such as in MP3-compressed audio. This is because audio compression removes parts of the music.
Some types of music which are particularly difficult to compress without noticing audio degradation.
Systems using audio compression are not able to deliver CD-quality audio.
Forward error correction adds additional data to the transmitted signal so that in cases where the
data may be corrupted during transmission, the original data can be recovered at the receiver. This
ensures a very robust transmission.
© 2004 Amphony 2
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