Published on Apr 29, 2016

Full review translated in English (Special thanks to Avmentor!)

KingSound is a company based in Hong Kong which is specialized in the
manufacture of loudspeakers and headphones showing special sympathy
for electrostatics. Right now they offer six electrostatic models, of which three are full range designs and the others are hybrid with
electrodynamic loudspeaker in low frequency range, three
amplifiers with push-pull output stages based on EL34 and KT88 tubes
and a preamplifier. The series electrostatic headphones
includes three models, the KS-H2, the KS-H3 and the new KS-H04
and two amplifiers specially designed for electrostatic headphones, the M-10
and the top M-20 model (tube OTL). The list of available
products closes a CD player, the CD-1, based on two PCM1742
different analog stages, a semiconductor and a vacuum tube (6N11).
During the exhibition in Munich last May, King Sound
first presented to the public a small, portable amplifier, the
first for mixed use (with dynamic and electrostatic headphones).
Available in a range of interesting colors, the M-03 is an opening
to users of dynamic headphones and, in parallel, a proposal
those of them would like some time to test the merits of a system
based on electrostatic units without having to worry
about the amplifier that will be needed.
The test in the following pages has as main object the M-03 and
the combination of the headphones H2 of the company with which it can
constitute an interesting bundle in quite an attractive price.
However, the temptation is to listen to the "small" compared with the amplifier of the desktop amps offered by King Sound with highly
interesting results. Let's look at the details ...

The M03 is a moderate volume portable headphone amplifier with dimensions
120x80x30 mm and weighing just over 400gr (including the batteries).
Unlike the generally Spartan logic that prevails in the two other
headphone amplifiers, King Sound selected, in the case of M-03,
a lighter approach with curved edges and finishes in a
variety of colors, so the device is pleasant to the eye and
friendly. From potential side, what makes the difference is the dual output offered. The M-03 can be used for driving the electrostatics via a special quintet plug (which carries, besides the audio a
high bias voltage of the bulkheads in 550V) and for driving
conventional, dynamic headphones via a mini jack (TRS) 3.5mm.

The user has at his disposal level slider (which plays the role
switch on / off) as well as a USB-A port through which it can be
charged the source. The use of M-03 as "Power bank" are especially
useful and is supported by a pair Li-Ion batteries with a total capacity of up to 6.2Ah and not only allows charging (at 5V / 1A) external devices but offers
substantial autonomy which, in the company reaches 13 hours (with charge
four hours, that is through a second micro-USB). The interior of the
amplifier is particularly concentrated as it includes, besides the two accumulators and two step-up transformers. One of the few things that are
apparent, it is understood that the amplifier is based on discrete semiconductors for strengthening the signal in a conventional level slider. The package
King Sound supplemented by a carry case, charger and a good
quality cable (TRS / TRS, 3.5mm) to connect the source to the amplifier.

Although much more strict aesthetic, the M10 is an interesting structure
which may be positioned vertically thereby providing a relative economy
space. Like the M-03 it is a completely "proportional" device, in that
not only provides an analog input which, however, is being implemented in two
types of connectors, RCA and mini jack 3.5mm which facilitates the connection
portable sources. The amplifier offers, even, an output-through connectors RCA- allowing the source connected to it to be driven in a conventional amplifier, if the user wants to use speakers. Except adjust the level, there is in front a set switch of bass that offers aid in that area.  The internal amp hides a structure based on discrete both components being preamp and the power stage, which
uses MOSFET designed for high voltage applications (two
D1NK60 per channel). A same component is used to stabilize
the headphone bias voltage. All circuits are based on materials
surface mount (except for some specific large parts of
size) and the power is very carefully, based on an annular
transformer with three secondary (two low voltage for the preamplifier and
a high for the polarization), "quick" lifts (with Schottky diodes) and
local consolidations.

The headphones used for the test were the H2, the lesser of
Both models of the company, until the announcement of a third model of the H-04 which is optimized for mobile use and presented recently. The H2 uses electrostatic units and is an over-ear design the main feature of which is the low weight and comfort as it weighs 420 grams. Electrostatic headphones have their own (sufficiently fanatical) public and have significant differences
compared with the dynamic, especially in the way we produce the sound wave, and can be regarded as a point source approach. This has two main effects, first smallest gain reduction as a function of the distance and, secondly, different
mechanical movement of the diaphragm (lower mass, more linear displacement,
without the forces present in a structure comprising a coil
moving), which results in less distortion.

The laboratory evaluation of the M-03 was made by the output dynamic headphones (TRS, 3.5mm) and the results should be evaluated carefully, particularly if someone wants to forward to the performance of the device when it leads electrostatic charges. This is mainly because the behavior of such loads is
expected to be significantly different than the typically smooth behavior of dynamic headphones and conventional resistive loads used during measurement.  In any case, however, the results may be regarded as indicative of the overall performance of the device.
The M-03 performed in the clipping threshold, 192mWrms load 32O, it
fell to 19.7mWrms when the load resistance rose to 600O, the
sensitivity of the device is near 300mVrms.  Deformations, generally were low levels of static  are in 0.016% and 0.006% (THD + N Cargo 32O and 600O, respectively) and 0.007% and 0.002% (IMD / SMPTE Cargo 32O and 600O). The amplifier proved also quite silent on the signal to noise ratio is at the
90dBr the area (A) with reference to 1/3 of maximum power.
The frequency response is flat over most of the range with mild cut in the low frequency range (-2dBr to 10Hz) and a small but clear intonation in the range of very high frequencies from 10kHzand above (+ 1dBr to 20kHz) which culminates in the 35kHz range over followed by mild rate (-3dB at 80kHz). This, obviously, is a premeditated behavior which is likely to take account of the
particularities of electrostatic headphones and / or in terms of the company for what should be the overall response of such a system.
The behavior of the amplifier in the frequency domain is practically independent
load (32 / 600O) and the differences between channels very small (0.025dBr
at 1kHz). The performance level of buffer is typically good, with tracking
remains in 0.5dBr area until halfway (from position zero attenuation) and reaches 3.2dBr to "quarter").
Based on this finding, it seems a good idea to one operates the M-03 with minor
impairments, as of course the headphones and the source permit.
The range of output for 1kHz reference signal with 1/3 of maximum power in
32O includes a large number of harmonics over the -100dBr stronger
which is the second (-80dBr) although the main feature, especially in
area of the first five harmonics, is the almost complete absence of
Intermodulation from the power supply that shines by its absence from the
final result.


Generally ... Description Technical Measurements Impressions-Conclusion

Frequency response for both channels. Level
Reference: 1/3 Pmax. Load 32O (green / red curve), 600O (orange / magenta).
Harmonics spectrum for signal 1kHz, reference level: 1/3  Pmax / 32O.

Carrying 600O, it is clear that the amplifier feel much more comfortable as
region of very high frequency (above 10kHz) cleans, total harmonics over the fourth well below the -100dBr and -
- second harmonic is now in the -90dBr region.
Similar general behavior (but different, of course, components)
we see the spectrum of intermodulation. The number of products is
greater in the case of measurement with load 32O but their level
It remains around and beneath -80dBr ...

... And significantly reduced in the case of measurement with load 600O, the
components have slightly higher level (in the area -75dBr).
The noise spectrum confirms the static measurements as a whole
Located beneath -120dBr (with reference to 1/3 of maximum power) and the hum they are barely discernible at 50Hz without further involvement. This of course is due to use batteries to power and the absence of transformer
rectification anywhere near the circuit. The device seems to "collect" little
high frequency noise as shown by the peaks appearing shortly
above 80kHz. This level, however, is close to thus -80dBr
It can hardly be a critical point.

The deformation depends on the frequency does not show special
changes. With load 32O moved between 0.1% and 0.09% having downward
trends as the input level increased and mild upward trend in the region
high frequency.
With load 600O behavior was even more good to the amplifier to move
to 0.05% for most of the spectrum (up to 10kHz). The worst
performance was low input level (-9dBr) so the curve moved in
region of 0.1%.

Finally, the variation of the deformation diagram in function of the power
output shows what, you would expect based on the overall picture of
Device: With load 32O amplifier moves to higher overall
deformation when driven within the limits of its validity. His behavior
around the point where they start the first effects of overloading are
smooth, but the slope and large shearing comes directly over
from this point.
THD + N as a function of the output power. Load 600O (green curve) and 32O (red curve).


Accoustic evaluation

The acoustic assessment of King Sound devices was done in two phases
each one of the two amplifiers to be required to drive the headphones of the
company. Given that the main objective of the test was M-03
directed mainly around it and the relationship with his M-10.
It includes data on both for the same headphones.
A small part of the hearings were finally done by the M-03 with the
reference headphones (Grado RS-2) through the output for dynamic headphones. In all cases, the amplifier was operated with the battery without
connecting the charger. The headset itself proved particularly comfortable being, perhaps, the most convenient system we have tested to date and despite their size can clearly be used when the user is in motion; not tiring at all, adapted very
easily and they isolate outside noise. It is understood that these features play a significant role in domestic use. In practice, after a while you forget them, which should be regarded as a particularly positive feature.

Starting from the M-10 / H2 system, the first impression one has is that
It has to do with a very pleasant, the limits of euphony, system puts
the listener into the music without particular difficulties and allows
lengthy hearings without the slightest problem.
The low, seemed to have good stretch and control to maintain the character at
quite high levels (certainly higher inadmissibly for long-term use)
while the use of low frequency control switch operates in moderation,
without excesses, and depending on the recording - usually constructive. The
system seemed to have good potential in the description details and
pulse in the region and the fact that in some cases may
seemed a little slow (relative to the reference: Melos Plus Series Line /
Grado RS2) yielded very good rhythmic parts, being filled and controlled. The middle region was pleasantly bright and warm, with a good sense of proximity, good features detailed and good performance of the human voice with clear description of the relationship of the performers with the rest
orchestra instruments. The high frequencies sounded complete with a
little fast depreciation in relation to what I am used to reference and
good harmonic richness that creates a whole sense of a mild nature
(Confirming, in essence, the initial impressions).
In summary, it could be said that the couple M-10 / H2 is a system
designed with mind to music lovers (who has a great record collection,
often with poor quality and rough recordings). Perhaps it is not what most
expensive but we've heard, certainly the end result is really
very pleasant and will delight many listeners.

On this basis one might assume that the M-03 will be a
"Portable version" of the M-10, more aesthetically elegant, with a view to
user smartphones and similar devices. However, King Sound seems to have
followed a quite different way here despite the fact that
we don’t know many details of the design, (due to compact
Construction of) the M-03 proved in practice a completely different ...
fruit!
The first impression gained is that someone in Hong Kong (headquarters
KS) decided to exhaust the potential of H2 in the accuracy issues and
opportunities and generally made this amplifier (although we have no
experience with the top tubed M-20). The system
M-03 / H2 sounded much more nimble, lively and bright, more accurate and
more features in micro dynamics and description of spaces,
following a completely different path compared to what we got from the
pair of M-10 / H2. The low maintained proper scope and control of M-10 and
it seemed to offer a little more volume and dynamics, being -in case-
more imposing without ever exaggerating. The bodies of the region
assigned to correct pulse and scale and rhythm parts were a little faster
maintaining, however, the sense of control and completeness. The middle
area was more vibrant, brighter and present with respect to that of the M
10, bringing the listener closer to the details and the structure of the piece
and maintaining (although to a lesser extent) the view and the laid-back aesthetic which seems to be a main of King Sound. The voices are very
good and realistic in presence, focused in the area of comfort (with the
characteristic way headset, however, between the ears) and motion
the sound sources described very well so some very active in this area mixes sound very interesting and attractive. The upper area sounded much more complete and extensive with very good description of the body and damping and pleasant brisk character. The M-03 / H2 couple seemed to have better possibilities to description of harmonics sounded more "present" and pleasant and compared to the M-03 M-10 and seemed more dark and sui generis.

The last step of the test involved the evaluation of M-03 used with
conventional dynamic headphones primarily in defining the role of H2 in the picture that we formed for both enhancers.
With the M-03 to drive the RS-2 Grado effect was particularly
good, well above what we are able to provide with the output stage
headphones Melos. With the amplifier of King Sound effect approached with
the comfort level of the headphones themselves (as I know through some
leading headphone amps has been to try in recent years).
This includes very good area and volume low, perfectly rhythmic parts with
very good speed and respectable punch, detailed midrange with great
description of rooms and good bar area, with lively and pleasant character
which, in some cases, rather deviated to the bright, without
unpleasant or hard. The fact that the M-03 revealed with great ease
the properties of Grado only as positive could be taken and indeed with
the basis of all of the test, it could be said that this is a
amplifier that maintains its accuracy over a pleasant character and
allow headphones to unfold their attributes and options in their design.
What they mean, finally, all this for the H2;
Starting indirectly conclusions (based on the behavior of the pair M-
03 / H2 and M-03 / Grado RS-2) could be said that this is a
headphone system that emphasizes relaxed, hours of hearings
offering an airy, bright and mild in character performance really
will match every musical genre, an audiophile / all-around headset high
level that is able to offer highly enjoyable experience for the listener.

Finally...

... Three testing devices Kingsound the first conclusion, rightly, concerns the whole company and its people who obviously know ... the art very well: use the characteristics of
electrostatic headphones perfectly, and can tailor their products to
different needs / views.
The M-10 / H2 couple is a carefully designed system with emphasis on pleasing / mild character, while the couple
M-03 / H2 places greater emphasis on dynamism and precision, proof that
there are no preconceptions and sticking to schools and doctrines.  The M-03
is a portable amplifier with very good possibilities on issues of accuracy
which is cut and sewn to the measures of demanding / on-the-go listeners
not wanting to miss the use of electrostatic headphones (or if not, want
to keep open the prospects of the future!). Add to that the
reasonable prices of the company and you we have an
extremely interesting proposal!

Dimitris Stamatakos

Original review can found in the link here

<< Go back to the previous page