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 Fosi Audio GR40

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 Fosi Audio GR40 (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	10.0/10.0	dBV
	3.2/3.2	V_RMS
Current: Linear Mode / Maximum or before clipping level	7.5/36.7	dB(mA)
	2.4/68.3	mA

General data - Signal/Noise
	RMS		dBFS (C)		dBFS (A)		dBFS 22 - 22k UNW
	Left	Right	Left	Right	Left	Right	Left	Right
Signal-to-noise ratio from the minimum background noise level, dB	-91.06	-91.04	-93.92	-93.95	-98.22	-98.25	-91.12	-91.05
Volume control range, dB	113.07				113.00
Noise floor level at the minimum volume level position, dBV	-81.01	-80.99	-83.87	-83.90	-88.17	-88.20	-81.07	-81.00
Noise floor level at the minimum volume level position, µV_RMS	89.02	89.22	64.04	63.82	39.04	38.90	88.41	89.12
Optimal range of volume control, dB	20.85	20.80	23.82	23.85	27.92	27.95	20.92	20.85
Maximum level at 0 dBFS, dBV	10.05				10.05
Additional information
Signal-to-noise at maximum volume level, dB	-90.85	-90.80	-93.82	-93.85	-97.92	-97.95	-90.92	-90.85
Noise floor level at maximum volume level, dBV	-80.80	-80.75	-83.77	-83.80	-87.87	-87.90	-80.87	-80.80
The difference in noise floor from the minimum and maximum volume levels, dB	0.21	0.24	0.10	0.10	0.30	0.30	0.20	0.20

Brief information

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

Frequency response Fosi Audio GR40 (as headphone amplifier)

Graphics setting view

Channel

Range

Channel:	Left	Right
Variation in frequency response in band from 40 Hz - 15 kHz	-0.5, +0.3	-0.4, +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

Impedance Fosi Audio GR40 (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	0.1	0.1	ohm
The maximum value in band from 40 Hz - 15 kHz	0.2	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 Fosi Audio GR40 (as headphone amplifier)

Graphics setting view

Channel

Range

Load

Channel:	Left	Right
Crosstalk @ 1 kHz @ 15.8 ohm	-54.3	-55.4	dB
Crosstalk @ 1 kHz @ 24.5 ohm	-57.7	-58.8	dB
Crosstalk @ 1 kHz @ 30.5 ohm	-60.0	-60.8	dB
Crosstalk @ 1 kHz @ 62.4 ohm	-65.6	-67.2	dB
Crosstalk @ 1 kHz @ 100.0 ohm	-70.0	-72.4	dB
Crosstalk @ 1 kHz @ 198.9 ohm	-78.0	-77.4	dB
Crosstalk @ 1 kHz @ 300.0 ohm	-77.4	-81.1	dB
Crosstalk @ 1 kHz @ 763.0 ohm	-83.1	-80.4	dB
Crosstalk @ 1 kHz @ Not loaded	-87.1	-85.7	dB

Brief information

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

Crosstalk Phase Fosi Audio GR40 (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 Fosi Audio GR40 with resistive load

Graphics setting view

Channel

Range

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

Channel:	Left	Right
TEST 16 ? + Fosi Audio GR40	0.0	0.1	dB
TEST 32 ? + Fosi Audio GR40	0.0	0.0	dB
TEST 64 ? + Fosi Audio GR40	0.0	0.0	dB
TEST 126 ? + Fosi Audio GR40	0.0	0.0	dB
TEST 256 ? + Fosi Audio GR40	0.0	0.0	dB
TEST 512 ? + Fosi Audio GR40	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 Fosi Audio GR40 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 ? + Fosi Audio GR40	0.0	0.0	dB
Grado GH4 Limited Edition + Fosi Audio GR40	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 Fosi Audio GR40 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 ? + Fosi Audio GR40	0.0	0.0	dB
Campfire Audio Andromeda + Fosi Audio GR40	0.3	0.3	dB
Fearless Audio S8F Freedom + Fosi Audio GR40	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 Fosi Audio GR40

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 Fosi Audio GR40

Graphics setting view

Type of chart

RAW coordinates

Power characteristics of the	Voltage		Current
	dBV	V_RMS	dB(mA)	mA
Linear Mode	10.0	3.2	7.5	2.4
Optimal Mode	10.0	3.2	36.7	68.3
Hard Mode	10.0	3.2	36.7	68.3
Maximum mode	10.0	3.2	36.7	68.3

Volume Control Type	Analog
Optimal range of volume control	36.0	dB

Comparison Fosi Audio GR40 and another amplifiers by loudness (Volume Level)

Main characteristics of the Fosi Audio GR40

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 Fosi Audio GR40

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	-29.3	0.0	0.7	0.0	0.7	0.0	0.7	0.0
24.5 ohm	-26.9	0.0	3.1	0.0	3.1	0.0	3.1	0.0
30.5 ohm	-25.4	0.1	4.6	0.1	4.6	0.1	4.6	0.1
62.4 ohm	-23.8	0.1	6.2	0.1	6.2	0.1	6.2	0.1
100 ohm	-16.9	0.1	8.1	0.1	8.1	0.1	8.1	0.1
198.9 ohm	-12.6	0.2	8.4	0.2	8.4	0.2	8.4	0.2
300 ohm	6.6	2.1	8.6	2.1	8.6	2.1	8.6	2.1
763 ohm	10.0	3.2	10.0	3.2	10.0	3.2	10.0	3.2
Not loaded	10.0	3.2	10.0	3.2	10.0	3.2	10.0	3.2

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	6.7	2.2	36.7	68.3	36.7	68.3	36.7	68.3
24.5 ohm	5.3	1.8	35.3	58.0	35.3	58.0	35.3	58.0
30.5 ohm	4.9	1.8	34.9	55.6	34.9	55.6	34.9	55.6
62.4 ohm	0.3	1.0	30.3	32.7	30.3	32.7	30.3	32.7
100 ohm	3.1	1.4	28.1	25.4	28.1	25.4	28.1	25.4
198.9 ohm	1.4	1.2	22.4	13.2	22.4	13.2	22.4	13.2
300 ohm	17.1	7.2	19.1	9.0	19.1	9.0	19.1	9.0
763 ohm	12.4	4.2	12.4	4.2	12.4	4.2	12.4	4.2

Power

Load	Linear Mode		Optimal Mode		Hard Mode		Max, before clipping
	dBm	mW	dBm	mW	dBm	mW	dBm	mW
15.8 ohm	-11.3	0.1	18.7	73.7	18.7	73.7	18.7	73.7
24.5 ohm	-10.8	0.1	19.2	82.5	19.2	82.5	19.2	82.5
30.5 ohm	-10.2	0.1	19.7	94.4	19.7	94.4	19.7	94.4
62.4 ohm	-11.7	0.1	18.3	66.9	18.3	66.9	18.3	66.9
100 ohm	-6.9	0.2	18.1	64.5	18.1	64.5	18.1	64.5
198.9 ohm	-5.6	0.3	15.4	34.8	15.4	34.8	15.4	34.8
300 ohm	11.9	15.4	13.9	24.3	13.9	24.3	13.9	24.3
763 ohm	11.2	13.3	11.2	13.3	11.2	13.3	11.2	13.3

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 Fosi Audio GR40 (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 Fosi Audio GR40 (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 Fosi Audio GR40 (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 Fosi Audio GR40 (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 Fosi Audio GR40 were carried out by Roman Kuznetsov on the hardware-software complex RAA.

The Fosi Audio GR40 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.

Fosi Audio GR40 is available in reports and services. You are in a professional report.

Information for entry level users

report for a newbie

The automatic selection of the optimal AMP models

Information for all

Versus of characteristics

Information for professionals

reports for a pro (Headphone amplifier)

Headphone amplifier

reports for a pro (DAC Line Out)

DAC Line Out

Comparison of on-line graphs

Quick jump to the schedule in this report:

Original text in Russian page. Translation page is not yet ready

You can help with translation via the: facebook and feedback.

Comments

No comments to Fosi Audio GR40

Want to leave a comment or ask a question? Register now or log in

	Login	Password
You are logged in as guest
Setting	Register	Forgot your password?