Tests and on-line comparison services
Astell&Kern AK380 AMP
Headphone AMPs (or as a headphone amplifiers)
Simple test reports for "dummies":
Balanced Hi
Balanced Norm
Unbalanced Hi
Unbalanced Norm
Профессиональные отчеты:
Balanced Hi
Balanced Norm
Unbalanced Hi
Unbalanced Norm
On-line comparison services with Astell&Kern AK380 AMP
Comparison of change the frequency response of joint work of Astell&Kern AK380 AMP with different headphones
Comparison of amplifier voltage and headphone sensitivity for optimal sound playing
Comparison of voltage graphs
Comparison of characteristics:
Balanced Hi
Balanced Norm
Unbalanced Hi
Unbalanced Norm
Volume comparison:
Balanced Hi
Balanced Norm
Unbalanced Hi
Unbalanced Norm
Amplifier tested with AK300
About of default amplifier of players AK300/320
Till now only were tested
AK300 and
AK320 DAPs in the Reference Audio Analyzer. The power of AK300 and AK320 amplifying part are near the same.
This grapth in on-line service
On the graph horizontal upper scale indicates the impedances of the headphones in ohms, which are connected to the amplifier. The right vertical scale indicates the voltage in decibels (dBV).
If we compare AMPs in
maximum mode (before the clipping zone of signal), we can see that the maximum voltage value is 6 dBV in the balanced and unbalanced mode.
The AK320 have about 7 dBV in maximum mode, and the AK300 have slightly less than 6 dBV. The difference in loudness is 1 dB. It is possible that from one sample to another sample players can be a little quieter or little louder. The level for current is similarly higher for AK320 by 1-2 dB depending on the mode.
The maximum output current in the balanced mode is lower. The difference in current between the balanced and unbalanced mode is 6 dB. That means two times less current level in balanced mode. The reason of the limit is in the total current consumption by amplifier. An amplifier consumes current regardless of whether it play a sound or not. In the balanced mode the number of operating amplifiers doubles. So if the player will not limitat the current, the operating time of the player can be significantly reduced which cause complaints from the user.
The ideal case is to have option in player to turn off the limit by current. The player's owner must have notice that player about reduced of player working time.
In this case, the balanced output for the low-impedance load is less powerful. When you switch to the balanced output it is possible to hear a "wheeze" that was absent at the unbalanced output on the same level of loudness.
The balanced output recommended be used with high-sensitivity IEM headphones.
This grapth in on-line service
If we look at the graphs in the maximum quality mode (in equivalent class A), then for AK300, the maximum voltage level in the balanced mode is slightly reduced due to the simpler implementation of the DAC.
The output current in the balanced mode is lower than in the unbalanced mode. The difference is 10 dB.
What changes when connecting AK380 AMP?
Unbalanced mode
This grapth in on-line service
The amplifier has two modes of gain: Normal and Hi.
In the normal mode, the parameters and capabilities are the same as the AK300 / AK320 standard (internal) amplifiers. In the Hi mode, the voltage is more on 3.5 dB, and the output current is the same level. So, this mode will be useful primarily for high-impedance headphones or listening to quiet recordings. If, for example, low-impedance headphones are not played well from a default amplifier AK300/320, the AK380 AMP will not improve sound.
Balanced Mode
This grapth in on-line service
In the balanced mode, according to the criteria of
equivalent class A in Norm mode, the voltage level is comparable with AK300 due to the characters of the spectra with the DAC from AK300. If the AK380 AMP was tested with AK320, then the voltage level would be higher. Thus, the Norm mode repeats the default amplifier. As opposed unbalanced amplifier in balanced amplifier output current is more on 4-6 dB. And, if we consider the criterion of
the equivalent class AB, the limitation is shifted additionally on 8 dB. This is a good boost for low-impedance headphones with medium and low sensitivity.
In the Hi mode, the voltage level becomes a highest for portable players, almost to 15 dBV. The manufacturer wrote is 18 dBV (8 VRMS) in the specifications. But in practice, above 15 dBV at the amplifier output the signal begins clipping. An additional 3 dB is worth considering as an additional pre-amplification for quiet music, as adding the volume before a DAC.
15 dBV is a high value not only by the standards of portable devices, but also by stationary amplifiers. The only downside to this gain can be audible background noise when using high-sensitivity headphones. Fortunately, switching Hi / Norm hardware and in Norm mode background noise is quieter.
In addition to the voltage in this mode, the output current also increases by 6 dB! In standard player amplifiers, it was different.
Сonclusion
Thus the additional amplifier Astell & Kern AK380 AMP is mostly demand for balanced over-ear headphones with low-sensitivity.
