Amphony h2500 情報ガイド
Q: What does the noise shaping filter of the Model 2500 headphones do ?
A: Digital audio, such as audio on a CD and the audio transmitted to the headphones, is represented
by numbers that represent voltage levels. When analog audio is converted to digital audio, the voltage
of the audio signal is sampled and represented by a number that refers to the voltage that comes
closest to the actual voltage. Because there is usually a small difference between that voltage and the
actual voltage of the analog audio signal, a certain amount of noise - quantization noise - is
introduced. The amount of such quantization noise is, among other things, determined by the amount
of information that is used to represent each sample - resolution. Therefore, digital audio on a CD and
audio transmitted to the headphones always contains a small amount of quantization noise which
limits the maximum possible signal-to-noise ratio of the transmission. In order to increase the signal-
to-noise ration beyond that limit, the Model 2500 headphones feature a special noise shaping filter
which is a 5th-order filter that outputs the audio at 64 times the sampling frequency and shifts the
audio data quantization noise to higher frequencies that are outside of the audible frequency band. As
a result, the Model 2500 is able to achieve a higher signal-to-noise ratio than would be possible
without a noise shaping filter.
by numbers that represent voltage levels. When analog audio is converted to digital audio, the voltage
of the audio signal is sampled and represented by a number that refers to the voltage that comes
closest to the actual voltage. Because there is usually a small difference between that voltage and the
actual voltage of the analog audio signal, a certain amount of noise - quantization noise - is
introduced. The amount of such quantization noise is, among other things, determined by the amount
of information that is used to represent each sample - resolution. Therefore, digital audio on a CD and
audio transmitted to the headphones always contains a small amount of quantization noise which
limits the maximum possible signal-to-noise ratio of the transmission. In order to increase the signal-
to-noise ration beyond that limit, the Model 2500 headphones feature a special noise shaping filter
which is a 5th-order filter that outputs the audio at 64 times the sampling frequency and shifts the
audio data quantization noise to higher frequencies that are outside of the audible frequency band. As
a result, the Model 2500 is able to achieve a higher signal-to-noise ratio than would be possible
without a noise shaping filter.
Q: What audio level is required from my audio source to be able to connect to the transmitter ?
A: The transmitter of the Model 2500 headphones features an analog audio interface level control that
allows the transmitter to be adjusted to work with audio sources delivering audio at levels anywhere
from 0.2 Vrms to 10 Vrms. This range covers most commercial and consumer audio equipment. By
being able to adjust the level of the audio interface, the full dynamic range of the digital transmission
can be used.
allows the transmitter to be adjusted to work with audio sources delivering audio at levels anywhere
from 0.2 Vrms to 10 Vrms. This range covers most commercial and consumer audio equipment. By
being able to adjust the level of the audio interface, the full dynamic range of the digital transmission
can be used.
Q: Will my 5.8 GHz cordless telephone or wireless LAN affect the operation of the headphones
or vice versa ?
or vice versa ?
A: Wireless LANs typically work at 2.4 GHz and will not affect the operation of the headphones, nor
will any 2.4 GHz cordless phones or Bluetooth devices. However, some 5.8 GHz cordless phones may
cause the headphones to mute. The range of the headphones may also be affected during the
operation of other 5.8 GHz equipment. If you do operate a 5.8 GHz cordless telephone, we
recommend that you purchase one of our 2.4 GHz models to eliminate any possibility of interference.
Whether or not the headphones will be affected by other 5.8 GHz devices depends to a large degree
on the type of equipment and the distance between such equipment and the headphones relative to
the headphones transmitter. Digital cordless telephones are more likely to cause problems than analog
cordless telephones. The base station of certain types of cordless telephones, such as the Panasonic
Gigarange series, will periodically broadcast signal beacons, even when the telephone is not in use,
that may cause a clicking noise of the headphones. Walls located between such equipment and the
headphones will in many cases attenuate an interfering signal enough for it not to cause any problems
when operating the headphones. The headphones employ an error correction scheme and thus can
tolerate interference up to a certain degree without any signal degradation. If interference is a problem
and if there is no direct line-of-sight to the headphones transmitter then the use of RangeBooster
modules is recommended.
will any 2.4 GHz cordless phones or Bluetooth devices. However, some 5.8 GHz cordless phones may
cause the headphones to mute. The range of the headphones may also be affected during the
operation of other 5.8 GHz equipment. If you do operate a 5.8 GHz cordless telephone, we
recommend that you purchase one of our 2.4 GHz models to eliminate any possibility of interference.
Whether or not the headphones will be affected by other 5.8 GHz devices depends to a large degree
on the type of equipment and the distance between such equipment and the headphones relative to
the headphones transmitter. Digital cordless telephones are more likely to cause problems than analog
cordless telephones. The base station of certain types of cordless telephones, such as the Panasonic
Gigarange series, will periodically broadcast signal beacons, even when the telephone is not in use,
that may cause a clicking noise of the headphones. Walls located between such equipment and the
headphones will in many cases attenuate an interfering signal enough for it not to cause any problems
when operating the headphones. The headphones employ an error correction scheme and thus can
tolerate interference up to a certain degree without any signal degradation. If interference is a problem
and if there is no direct line-of-sight to the headphones transmitter then the use of RangeBooster
modules is recommended.
Q: Can more than one set of headphones be used at the same time ?
A: It is possible to purchase additional headphones individually which can be operated from the same
transmitter. Please contact your dealer for more information.
transmitter. Please contact your dealer for more information.
© 2004 Amphony 3