This is a report for professionals with a suite of test of headphone amplifier.
You can see a simple report for "dummies" with explanations of the main characteristics for JCALLY JM20

A suite of tests for a headphone amplifier can be applied to just a universal output without a formal presence of an amplifier, if in this mode you can connect headphones to this output. Based on the results of the tests, you can understand the real picture, is the output powerful enough or not, with the initial data on the circuitry as a "black box".

Line-out, differences from the output for headphones and speakers

Advantages and disadvantages of balanced amplifiers

Test report - general data JCALLY JM20 (as headphone amplifier)

Frequency response, Impedance and Frequency response with standard headphones

Voltage levels from the load at the output of the amplifier

The main parameters of the universal block diagram of the amplifier
Average value of impedance band in 40 Hz - 15 kHz	0.1	ohm
Voltage: Linear Mode / Maximum or before clipping level	5.9/5.9	dBV
	2.0/2.0	V_RMS
Current: Linear Mode / Maximum or before clipping level	17.3/35.8	dB(mA)
	7.3/61.9	mA

General data - Signal/Noise
	RMS		dBFS (C)		dBFS (A)		dBFS 22 - 22k UNW
	Left	Right	Left	Right	Left	Right	Left	Right
Signal/Noise, dB	-124.88	-124.57	-128.99	-129.11	-129.89	-129.91	-126.29	-126.41
Noise floor level, dBV	-119.00	-118.69	-123.11	-123.23	-124.01	-124.03	-120.41	-120.53
Noise floor level, µV_RMS	1.12	1.16	0.70	0.69	0.63	0.63	0.95	0.94
Optimal range of volume control, dB	54.88	54.57	58.99	59.11	59.89	59.91	56.29	56.41
Maximum level at 0 dBFS, dBV	5.88				5.88

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

Frequency response JCALLY JM20 (as headphone amplifier)

Graphics setting view

Channel

Range

Channel:	Left	Right
Variation in frequency response in band from 40 Hz - 15 kHz	-0.1, +0.0	-0.1, +0.0	dB

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

On the frequency response comparison page, there is an export option and additional tools for adjusting the frequency response

Impedance JCALLY JM20 (as headphone amplifier)

Graphics setting view

Channel

Channel:	Left	Right
Impedance average in band from 40 Hz - 15 kHz	0.1	0.1	ohm
The minimum value in band from 40 Hz - 15 kHz	0.0	0.0	ohm
The maximum value in band from 40 Hz - 15 kHz	0.1	0.1	ohm

Comparison of basic characteristics AMPs

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

Crosstalk JCALLY JM20 (as headphone amplifier)

Graphics setting view

Channel

Range

Load

Channel:	Left	Right
Crosstalk @ 1 kHz @ 15.8 ohm	-59.8	-59.6	dB
Crosstalk @ 1 kHz @ 24.5 ohm	-63.3	-63.2	dB
Crosstalk @ 1 kHz @ 30.5 ohm	-65.5	-65.2	dB
Crosstalk @ 1 kHz @ 62.4 ohm	-71.6	-71.5	dB
Crosstalk @ 1 kHz @ 100.0 ohm	-75.8	-75.5	dB
Crosstalk @ 1 kHz @ 198.9 ohm	-80.6	-81.2	dB
Crosstalk @ 1 kHz @ 300.0 ohm	-84.6	-85.1	dB
Crosstalk @ 1 kHz @ 763.0 ohm	-92.8	-93.4	dB
Crosstalk @ 1 kHz @ Not loaded	-106.7	-106.6	dB

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

Crosstalk Phase JCALLY JM20 (as headphone amplifier)

Graphics setting view

Channel

Load

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

Frequency response JCALLY JM20 with resistive load

Graphics setting view

Channel

Range

Frequency response of amplifier with resistive load @ 40 Hz - 15 kHz

Channel:	Left	Right
TEST 16 ? + JCALLY JM20	0.1	0.1	dB
TEST 32 ? + JCALLY JM20	0.0	0.0	dB
TEST 64 ? + JCALLY JM20	0.0	0.0	dB
TEST 126 ? + JCALLY JM20	0.0	0.0	dB
TEST 256 ? + JCALLY JM20	0.0	0.0	dB
TEST 512 ? + JCALLY JM20	0.0	0.0	dB

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

On the frequency response comparison page, there is an export option and additional tools for adjusting the frequency response

Frequency response JCALLY JM20 loaded dynamic headphone type

Graphics setting view

Channel

Range

Frequency response of amplifier loaded dynamic headphone type @ 40 Hz - 15 kHz

Channel:	Left	Right
TEST 10000 ? + JCALLY JM20	0.0	0.0	dB
Grado GH4 Limited Edition + JCALLY JM20	0.0	0.0	dB

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

On the frequency response comparison page, there is an export option and additional tools for adjusting the frequency response

Frequency response JCALLY JM20 loaded type balance armature headphone type

Graphics setting view

Channel

Range

Frequency response of amplifier loaded type balance armature headphone type @ 40 Hz - 15 kHz

Channel:	Left	Right
TEST 10000 ? + JCALLY JM20	0.0	0.0	dB
Campfire Audio Andromeda + JCALLY JM20	0.2	0.2	dB
Fearless Audio S8F Freedom + JCALLY JM20	0.2	0.2	dB

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

On the frequency response comparison page, there is an export option and additional tools for adjusting the frequency response

THD vs load vs output voltage JCALLY JM20

Graphics setting view

Channel

Load

Harmonic, number

Range

Graphics setting view

Channel

Load

Harmonic, number

Range

Graphics setting view

Channel

Load

Range

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

Maximum voltage output level vs load JCALLY JM20

Graphics setting view

Type of chart

RAW coordinates

Power characteristics of the	Voltage		Current
	dBV	V_RMS	dB(mA)	mA
Linear Mode	5.9	2.0	17.3	7.3
Optimal Mode	5.9	2.0	35.8	61.9
Hard Mode	5.9	2.0	35.8	61.9
Maximum mode	5.9	2.0	35.8	61.9

Volume Control Type	Digital
Optimal range of volume control	59.0	dB
Signal/Noise / Maximum	129.0/5.9	dB/dBV
Signal/Noise @ -14.9 dBV 32 ohm (1 mW)	108.20	dB
Signal/Noise @ -5.2 dBV 300 ohm (1 mW)	117.89	dB

Comparison JCALLY JM20 and another amplifiers by loudness (Volume Level)

Main characteristics of the JCALLY JM20

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

Maximum voltage output level vs load JCALLY JM20

Graphics setting view

Type of chart

RAW coordinates

Maximum Amplifier Voltage Level

Load	Linear Mode		Optimal Mode		Hard Mode		Max, before clipping
	dBV	V_RMS	dBV	V_RMS	dBV	V_RMS	dBV	V_RMS
15.8 ohm	-15.2	0.2	-0.2	0.2	-0.2	0.2	-0.2	0.2
24.5 ohm	-13.2	0.2	1.8	0.2	1.8	0.2	1.8	0.2
30.5 ohm	-12.2	0.2	2.8	0.2	2.8	0.2	2.8	0.2
62.4 ohm	-5.1	0.6	3.9	0.6	3.9	0.6	3.9	0.6
100 ohm	3.9	1.6	4.9	1.6	4.9	1.6	4.9	1.6
198.9 ohm	3.9	1.6	4.9	1.6	4.9	1.6	4.9	1.6
300 ohm	5.9	2.0	5.9	2.0	5.9	2.0	5.9	2.0
763 ohm	5.9	2.0	5.9	2.0	5.9	2.0	5.9	2.0
Not loaded	5.9	2.0	5.9	2.0	5.9	2.0	5.9	2.0

Maximum level of amplifier current

Load	Linear Mode		Optimal Mode		Hard Mode		Max, before clipping
	dB(mA)	mA	dB(mA)	mA	dB(mA)	mA	dB(mA)	mA
15.8 ohm	20.8	11.0	35.8	61.9	35.8	61.9	35.8	61.9
24.5 ohm	19.0	9.0	34.0	50.4	34.0	50.4	34.0	50.4
30.5 ohm	18.2	8.1	33.2	45.5	33.2	45.5	33.2	45.5
62.4 ohm	19.0	8.9	28.0	25.0	28.0	25.0	28.0	25.0
100 ohm	23.9	15.6	24.9	17.5	24.9	17.5	24.9	17.5
198.9 ohm	17.9	7.9	18.9	8.8	18.9	8.8	18.9	8.8
300 ohm	16.3	6.6	16.3	6.6	16.3	6.6	16.3	6.6
763 ohm	8.2	2.6	8.2	2.6	8.2	2.6	8.2	2.6

Power

Load	Linear Mode		Optimal Mode		Hard Mode		Max, before clipping
	dBm	mW	dBm	mW	dBm	mW	dBm	mW
15.8 ohm	2.8	1.9	17.8	60.6	17.8	60.6	17.8	60.6
24.5 ohm	2.9	2.0	17.9	62.2	17.9	62.2	17.9	62.2
30.5 ohm	3.0	2.0	18.0	63.0	18.0	63.0	18.0	63.0
62.4 ohm	6.9	4.9	15.9	39.0	15.9	39.0	15.9	39.0
100 ohm	13.9	24.4	14.9	30.7	14.9	30.7	14.9	30.7
198.9 ohm	10.9	12.3	11.9	15.5	11.9	15.5	11.9	15.5
300 ohm	11.1	12.9	11.1	12.9	11.1	12.9	11.1	12.9
763 ohm	7.1	5.1	7.1	5.1	7.1	5.1	7.1	5.1

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

Spectrum of Total Harmonic Distortion vs Level JCALLY JM20 (as headphone amplifier)

Graphics setting view

Channel

Level

Range

Graphics setting view

Channel

Level

Range

Graphics setting view

Channel

Shift

dBm

Range

Graphics setting view

Channel

Shift

dBV

Range

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

Spectrum of Multitone Distortion vs Level vs Load JCALLY JM20 (as headphone amplifier)

Graphics setting view

Channel

Level

Range

Graphics setting view

Channel

Level

Range

Graphics setting view

Channel

Shift

dBm

Range

Graphics setting view

Channel

Shift

dBV

Range

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

Spectrum of IMD SMPTE vs Level JCALLY JM20 (as headphone amplifier)

Graphics setting view

Channel

Level

Range

Range

Graphics setting view

Channel

Level

Range

Range

Graphics setting view

Channel

Shift

Range

dBm

Range

Graphics setting view

Channel

Shift

Range

dBV

Range

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

Spectrum of IMD CCIF vs Level JCALLY JM20 (as headphone amplifier)

Graphics setting view

Channel

Level

Range

Graphics setting view

Channel

Level

Range

Graphics setting view

Channel

Shift

dBm

Range

Graphics setting view

Channel

Shift

dBV

Range

Brief information

Clicking on the graph will take you to the comparison page of different models with advanced graph display settings.

More detailed

Measurements of JCALLY JM20 were carried out by Roman Kuznetsov on the hardware-software complex RAA.

The JCALLY JM20 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 iXBT.com

Information for Authors. You can freely use the graphics in your articles with a link to us.

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Comments

Justaway
Изображения, медиа и смайлы доступны в исходном чате.
2026-06-16 01:30:51

Комментарий к профессиональному отчету JCALLY JM20

А если на графике "Максимальный уровень напряжения в зависимости от нагрузки на выходе" наушники попадают в зелёную полосу вместо синей, это сильно плохо? Я так понимаю, там появляются гармоники высокого порядка, но они могут быть хоть на уровне -100Дб, это же не критично?

romanrex
Изображения, медиа и смайлы доступны в исходном чате.
2026-06-21 11:45:41

Комментарий к профессиональному отчету JCALLY JM20

Justaway 2026-06-16 01:30:51
Комментарий к профессиональному отчету JCALLY JM20
А если на графике "Максимальный уровень напряжения в зависимости от нагрузки на выходе" наушники попадают в зелёную полосу вместо синей, это сильно плохо? Я так понимаю, там появляются гармоники высокого порядка, но они могут быть хоть на уровне -100Дб, это же не критично?

В зеленую зону обычно попадает спектр, в котором есть гармоники высоких порядков, но они убывающие. Т.е. это скорее всего должно быть не слышно, но в теории можно предположить, что звучание будет не таким максимально хорошим, как в голубой зоне графика.
В отчете можно все эти спектры посмотреть отдельно, переключая номинал нагрузки (сопротивление наушников) и уровень основного тона.

Justaway
Изображения, медиа и смайлы доступны в исходном чате.
2026-06-28 06:26:24

Комментарий к профессиональному отчету JCALLY JM20

romanrex 2026-06-21 11:45:41
Комментарий к профессиональному отчету JCALLY JM20
В зеленую зону обычно попадает спектр, в котором есть гармоники высоких порядков, но они убывающие. Т.е. это скорее всего должно быть не слышно, но в теории можно предположить, что звучание будет не таким максимально хорошим, как в голубой зоне графика.
В отчете можно все эти спектры посмотреть отдельно, переключая номинал нагрузки (сопротивление наушников) и уровень основного тона.

Понял, спасибо. Просто обратил внимание, что у некоторых устройств весь график практически зелёный при хорошем запасе по мощности, как у того же sbx G6.

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