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Fosi Audio T20 User Manual
Product Specifications
Thanks again so much for your purchasing! This is a
creative audio amplifier for you, it combines the beauty of
traditional vacuum tube and the power of digital amplifier. It
has BASS & Treble adjustable function, Bluetooth apt-X
connection, support audio output through passive speaker
or 3.5mm headphone. And, the vacuum tube is also replace-
able as you like, it is a fantastic amplifier that suit for your
personal PC desk, book room, or for your home theater in
your living room. Bring joy and happiness to your smarter
life!
THD:
SNR:
Max Power Output:
≤ 0.04%
≥ 99dB
Power Adapter: 24V/4.5A
50W x 2@4Ω
Frequency Range: 20Hz - 20kHz (±1 dB)
Input Mode:
Bluetooth and AUX
Bluetooth Transmission
Distance:
Up to 50ft(15m)
Bluetooth Transmission
Distance:
Up to 50ft(15m)
Amplifier Chip: TPA3116
Input Sensitivity: ≤ 280mV
DC Input Range: 12V - 24V
Terminating Impedance: 2 Ω - 8 Ω
Product Overview & Control
Functions
Power Switch
Indicator Light
Bass Control Treble Control
Volume Control
3.5mm
Headphone Output
Front Panel
Back Panel
BT/AUX Mode Switch
Audio Input Speaker Output
DC Input
Bluetooth Antenna
Interface
Bluetooth
Antenna
Package Contents
T20 Tube Amplifier*1
Vacuum Tube*2
Bluetooth Antenna*1
24V/4.5A Power Adapter*1
User Manual *1
Quick Setup
Preparation
Prepare 1: T20, 24V power supply, passive speakers, speaker wires
or banana plugs;
Prepare 2: Insert the tube carefully and make sure that all pins are
fully inserted.
Prepare 3: • Connect the T20 to the passive speakers via the
speaker wires, you can connect the speaker's wire via
the bare wire or the banana plugs;
• Or Connect a wired headset to the Headphone Output
on the front panel of the T20, the speaker output will
disconnect once the headset is plugged in.
Prepare 4: Connect the 24V power supply to the DC input;
Prepare 5: Turn on the Power Switch.
Note: Before turning on the power switch of the amplifier, please
turn the volume button to the lowest position.
Note: Be sure that the power switch is on the OFF position before
connect the power supply. Please turn on the T20 first and
then turn on the speakers to avoid noise.
Package Contents
T20 Tube Amplifier*1
Vacuum Tube*2
Bluetooth Antenna*1
24V/4.5A Power Adapter*1
User Manual *1
Quick Setup
Preparation
Prepare 1: T20, 24V power supply, passive speakers, speaker wires
or banana plugs;
Prepare 2: Insert the tube carefully and make sure that all pins are
fully inserted.
Prepare 3: • Connect the T20 to the passive speakers via the
speaker wires, you can connect the speaker's wire via
the bare wire or the banana plugs;
• Or Connect a wired headset to the Headphone Output
on the front panel of the T20, the speaker output will
disconnect once the headset is plugged in.
Prepare 4: Connect the 24V power supply to the DC input;
Prepare 5: Turn on the Power Switch.
Note: Before turning on the power switch of the amplifier, please
turn the volume button to the lowest position.
Note: Be sure that the power switch is on the OFF position before
connect the power supply. Please turn on the T20 first and
then turn on the speakers to avoid noise.
Method 2: Banana plugs connection illustration
: Release the banana jacket;
: Loosen the screw;
: Insertion speaker wire and tighten the screw;
: Tighten the banana jacket;
: Insert the banana plug into the horn terminals of the
speaker and amplifier.
Note: Please make sure that the speakers’ wire are not attached
with each other, the speaker connection area is very
narrow, it is easy to cause the positive and negative
speakers’ wires to contact each other, which will result in
no sound output.
How to connect the speaker wire?
Method 1: Bare wire connection illustration
: Release the horn terminals block terminals;
: Insert the two ends of the speaker wire into the
amplifier and speaker terminal holes;
: Tighten the horn terminals;
Note: Please make sure that the speakers’ wire are not attached
with each other, the speaker connection area is very
narrow, it is easy to cause the positive and negative
speakers’ wires to contact each other, which will result in
no sound output.
1
2
3
4
5
1
2
3
1
2
3
Bluetooth Input
Prepare your Bluetooth device (take a phone as an example)
Step 1: Install the Bluetooth antenna.
Step 2: Select the input mode switch to BT on the back panel of
the T20, The indicator is blue and flashing.
Step 3: Turn on the Bluetooth on your phone and search “ Fosi
Audio” or “Fosi Audio T20”, the indicator stays blue after a
successful pairing.
Step 4: Open the audio application, play and enjoy!
AUX Input
Prepare: audio source (take a TV as an example), a RCA cable or a
3.5mm AUX to RCA cable.
Step 1: Select the input mode switch to AUX on the back panel of
the T20, the indicator light shows red light;
Step 2: Connect your TV to “Audio Input” via a RCA cable;
Step 3: Open your TV, play and enjoy!
Troubleshooting/QA
1: What type of speakers work best with T20 Amplifier?
• Fosi Audio Amplifiers work great with any 2-8 ohm passive
speakers. You can connect passive speakers via the Speaker
Output or active speakers via the Headphone Output.
Release Jacket Loosen Screw
Insertion speaker wire
tighten screw
Tighten Jacket
1
2 3 4
banana plug into
the horn terminals
5
2: Can I connect a turntable to T20 amp, why is the
volume is extremely Low?
• As for the turntables do not have a built-in preamp, you need to
add an external phono preamp before connecting T20, such as
our BOX X1, or BOX X2.
• As for the turntables which have a built-in preamp, you need to
switch the preamp on before connecting T20.
3: Why does the sound is cracking or make a lot of
electric noise?
• Please make sure all the cables completely pushed into the
devices, incompletely connection will cause this cracking.
• Please remove all the inputs then check whether cracking noise
disappear or not, the cracking maybe from the audio source or
input cables.
• If you are not using the original factory standard power supply,
please replace the power supply before testing. Many power
supply in the market have large interference coefficient, which
will cause a lot of current sound.
• Please check if the vacuum tube is completely plugged in, and try
to change the left and right vacuum tubes.
4: My Bluetooth device cannot pair with T20?
• Make sure that you have selected the input mode switch to BT on
the back panel of the T20.
• Make sure that T20 is powered on.
• Make sure that T20 is not paired with other devices.
• Make sure that the distance between your device and T20 is not
too long.
• Make sure there are no barriers between your device and T20,
barriers will affect the Bluetooth operation distance.
• Please reconnect the power supply to the T20, and move the T20
to another room to have a try.
Bluetooth Input
Prepare your Bluetooth device (take a phone as an example)
Step 1: Install the Bluetooth antenna.
Step 2: Select the input mode switch to BT on the back panel of
the T20, The indicator is blue and flashing.
Step 3: Turn on the Bluetooth on your phone and search “ Fosi
Audio” or “Fosi Audio T20”, the indicator stays blue after a
successful pairing.
Step 4: Open the audio application, play and enjoy!
AUX Input
Prepare: audio source (take a TV as an example), a RCA cable or a
3.5mm AUX to RCA cable.
Step 1: Select the input mode switch to AUX on the back panel of
the T20, the indicator light shows red light;
Step 2: Connect your TV to “Audio Input” via a RCA cable;
Step 3: Open your TV, play and enjoy!
Troubleshooting/QA
1: What type of speakers work best with T20 Amplifier?
• Fosi Audio Amplifiers work great with any 2-8 ohm passive
speakers. You can connect passive speakers via the Speaker
Output or active speakers via the Headphone Output.
2: Can I connect a turntable to T20 amp, why is the
volume is extremely Low?
• As for the turntables do not have a built-in preamp, you need to
add an external phono preamp before connecting T20, such as
our BOX X1, or BOX X2.
• As for the turntables which have a built-in preamp, you need to
switch the preamp on before connecting T20.
3: Why does the sound is cracking or make a lot of
electric noise?
• Please make sure all the cables completely pushed into the
devices, incompletely connection will cause this cracking.
• Please remove all the inputs then check whether cracking noise
disappear or not, the cracking maybe from the audio source or
input cables.
• If you are not using the original factory standard power supply,
please replace the power supply before testing. Many power
supply in the market have large interference coefficient, which
will cause a lot of current sound.
• Please check if the vacuum tube is completely plugged in, and try
to change the left and right vacuum tubes.
4: My Bluetooth device cannot pair with T20?
• Make sure that you have selected the input mode switch to BT on
the back panel of the T20.
• Make sure that T20 is powered on.
• Make sure that T20 is not paired with other devices.
• Make sure that the distance between your device and T20 is not
too long.
• Make sure there are no barriers between your device and T20,
barriers will affect the Bluetooth operation distance.
• Please reconnect the power supply to the T20, and move the T20
to another room to have a try.
• Restart the T20 and then try to connect again, try to use another
Bluetooth device.
5: Why Bluetooth is intermittent?
• Please try with another Bluetooth device.
• Make sure there is no interference from other electronic devices
between the T20 and the audio source.
• Place your device close to the T20, and plug in the power adapter
again.
6: How much power does it take in standby mode? Can
this amp be left on all the time?
• This is the class D amplifier, it will cost very low power when it is
in standby mode. It can be connected all the time and it is safe
without power consumption.
7: Sound quality is not good?
• Make sure all the cables are fully connected.
• Adjust the treble and bass control of the power amplifier to
achieve the right tone.
• Please try to change the sound source and cables to test.
• Please check if the vacuum tube is broken or completely plugged
in.
8: Can T20 accept signal from a Bluetooth microphone?
• Please make sure your Bluetooth microphone must be the
transmitter. Because T20 is a Bluetooth receiver amplifier.
• Please make sure that microphone's Bluetooth can be connected
to the T20's Bluetooth by your operation.
9: Why does the sound cut in and out?
• Please try to change the sound source.
• Lower the treble and bass of the T20.
• Restart the T20 and then try to connect again, try to use another
Bluetooth device.
5: Why Bluetooth is intermittent?
• Please try with another Bluetooth device.
• Make sure there is no interference from other electronic devices
between the T20 and the audio source.
• Place your device close to the T20, and plug in the power adapter
again.
6: How much power does it take in standby mode? Can
this amp be left on all the time?
• This is the class D amplifier, it will cost very low power when it is
in standby mode. It can be connected all the time and it is safe
without power consumption.
7: Sound quality is not good?
• Make sure all the cables are fully connected.
• Adjust the treble and bass control of the power amplifier to
achieve the right tone.
• Please try to change the sound source and cables to test.
• Please check if the vacuum tube is broken or completely plugged
in.
8: Can T20 accept signal from a Bluetooth microphone?
• Please make sure your Bluetooth microphone must be the
transmitter. Because T20 is a Bluetooth receiver amplifier.
• Please make sure that microphone's Bluetooth can be connected
to the T20's Bluetooth by your operation.
9: Why does the sound cut in and out?
• Please try to change the sound source.
• Lower the treble and bass of the T20.
• Make sure that the positive and negative terminals of the speaker
outputs do not touch each other. Some of the larger banana plugs
can easily touch each other and cause a short circuit
10: Can I bridge channel 1 and channel 2 to get 100watts?
• No, this amplifier can't be bridged.
11: Why does distortion occur?
• Because the vacuum tubes amplify the sound. If you turn the
sound up too loud, distortion may occur. Please try turning the
volume down a little.
12: Can I replace the vacuum tubes?
• If necessary, there are substitutions: EF95, 6AK5, 6AK5W,
403A/403B, 6J1, 6J1P, 6J2, 6J3, 6J4, 6J5 vacuum tubes, etc. You
can replace the vacuum tubes to DIY your stereo system.
Note: Please must remember switch off the power BEFORE you
pull out the tube, or it might damage the device.
13: Why the T20 came with a broken vacuum tube?
• Due to the long-distance, the vacuum tube may be damaged
during transportation. If you find that the vacuum tube is broken
or there is other problems, please contact our email, and we will
replace the vacuum tube for you.
14: Can headphones and speakers play at the same time?
• No, when the headphones plug in, the speakers' output will be
interrupted.
Output priority:
3.5mm Headphone Output > Speaker Output
15: How can I connect T20 to TV?
• The 3.5mm AUX jack is the audio input. It can through 3.5mm
AUX input to connect your TV.
16: Why there is no voice from my amplifier?
• Please check whether the cable of power supply is connected to
T20 and whether the power indicator is on.
• Make sure the T20's indicator light is on when the power is turned
on.
• Please check that the T20 and your source components are
turned on and not set to minimum volume, if possible replace
your source and test again.
• Check that the wire connections from the audio source to each
speaker in the amplifier are connected correctly.
• Please check that the cable is not loose, damaged. Incomplete
connection is one of the main reasons for no sound.
• Please make sure the Bluetooth is paired or not, if Bluetooth is
connected, AUX input will be disconnected. If you want to
connect this amplifier with a 3.5mm AUX cable, you need to
disconnect the Bluetooth first.
• Please make sure that the headset is connected or not. If the
headset is connected, the speaker will be disconnected.
17: Which Bluetooth chip does T20 have?
• The T20 is equipped with QCC3031 Bluetooth chip, which
supports Apple acc and aptx.
Note: QCC3031 Bluetooth chip does not support apt-X LL.
18: an I use Bluetooth head phones with this unit?
• This tube amplifier is a Bluetooth receiver, not a Bluetooth
transmitter. It works with 3.5mm wired headphones.
• Make sure that the positive and negative terminals of the speaker
outputs do not touch each other. Some of the larger banana plugs
can easily touch each other and cause a short circuit
10: Can I bridge channel 1 and channel 2 to get 100watts?
• No, this amplifier can't be bridged.
11: Why does distortion occur?
• Because the vacuum tubes amplify the sound. If you turn the
sound up too loud, distortion may occur. Please try turning the
volume down a little.
12: Can I replace the vacuum tubes?
• If necessary, there are substitutions: EF95, 6AK5, 6AK5W,
403A/403B, 6J1, 6J1P, 6J2, 6J3, 6J4, 6J5 vacuum tubes, etc. You
can replace the vacuum tubes to DIY your stereo system.
Note: Please must remember switch off the power BEFORE you
pull out the tube, or it might damage the device.
13: Why the T20 came with a broken vacuum tube?
• Due to the long-distance, the vacuum tube may be damaged
during transportation. If you find that the vacuum tube is broken
or there is other problems, please contact our email, and we will
replace the vacuum tube for you.
14: Can headphones and speakers play at the same time?
• No, when the headphones plug in, the speakers' output will be
interrupted.
Output priority:
3.5mm Headphone Output > Speaker Output
Our website: www.fosiaudio.com
Amazon store: www.amazon.com/fosiaudio
Our Youtube channel: Fosi Audio
Our Facebook page: Fosi Audio
After-sale Service and Technical Support Email:
support@fosiaudio.com
fosiaudio@hotmail.com
Warranty Information
• All Fosi Audio products have an 18-month limited warranty on
parts and labor from the date of purchase. Please contact us if
you have any problems.
About Fosi Audio
• Fosi Audio designs and builds innovative audio products with
all your music in mind. Great sound, simple but elegant
designs, high-quality materials, and truly useful features are
what Fosi Audio is about. We sincerely hope you get as much
enjoyment from our products as we’ve had to create them!
Fosi Audio Product’s User Manual
15: How can I connect T20 to TV?
• The 3.5mm AUX jack is the audio input. It can through 3.5mm
AUX input to connect your TV.
16: Why there is no voice from my amplifier?
• Please check whether the cable of power supply is connected to
T20 and whether the power indicator is on.
• Make sure the T20's indicator light is on when the power is turned
on.
• Please check that the T20 and your source components are
turned on and not set to minimum volume, if possible replace
your source and test again.
• Check that the wire connections from the audio source to each
speaker in the amplifier are connected correctly.
• Please check that the cable is not loose, damaged. Incomplete
connection is one of the main reasons for no sound.
• Please make sure the Bluetooth is paired or not, if Bluetooth is
connected, AUX input will be disconnected. If you want to
connect this amplifier with a 3.5mm AUX cable, you need to
disconnect the Bluetooth first.
• Please make sure that the headset is connected or not. If the
headset is connected, the speaker will be disconnected.
17: Which Bluetooth chip does T20 have?
• The T20 is equipped with QCC3031 Bluetooth chip, which
supports Apple acc and aptx.
Note: QCC3031 Bluetooth chip does not support apt-X LL.
18: an I use Bluetooth head phones with this unit?
• This tube amplifier is a Bluetooth receiver, not a Bluetooth
transmitter. It works with 3.5mm wired headphones.
