Comment on Astell&Kern AK380 AMP

Reports / Astell&Kern / AK380 AMP / Balanced Hi / Review

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Amplifier for players AK380, AK320 и AK300.

Amplifier tested with AK300.

About of default amplifier of players AK300/320

Till now only were tested Astell&Kern AK300 and Astell&Kern AK320 DAPs. The power of AK300 and AK320 amplifying part are near the same.

Maximum mode

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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.

Equivalent class A

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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

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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

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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.


Thus the additional amplifier Astell & Kern AK380 AMP is mostly demand for balanced over-ear headphones with low-sensitivity.


Measurements of Astell&Kern AK380 AMP Balanced Hi were carried out by Roman Kuznetsov on the hardware-software complex RAA.

The Astell&Kern AK380 AMP Balanced Hi test was conducted as a black box test, without regard to cost and prestige. This is the basic principle for making measurements, measurement reports and developing tests in RAA.

I believe that it is important to do not make an absolute assessment of the device, but an aggregate assessment when working together with a headphones and taking into account external factors. This allows you to effectively reveal the potential of the entire set of devices or to make a more optimal choice of components.

Kuznetsov Roman
Founder of RAA

Known by the nickname romanrex
Аuthor of articles

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