GR40 - Audio Amplifier Fosi Audio - Free user manual and instructions

Product Type	Bluetooth Audio Receiver
Brand	Fosi Audio
Model	GR40
Bluetooth Version	5.0
Bluetooth Codecs	aptX HD, aptX, SBC, AAC
Audio Output	RCA (L/R) and 3.5mm jack
Power Supply	5V DC via Micro USB
Dimensions (approx)	4.3 x 3.5 x 0.9 inches (110 x 90 x 23 mm)
Weight (approx)	4.9 oz (140 g)
Range	Up to 33 ft (10 m) in open space
Compatibility	TVs, stereos, speakers with AUX or RCA input
Features	Wireless music streaming, hands-free calling, low latency
LED Indicator	Blue for connected, flashing for pairing
Controls	Power/Multi-function button
Cleaning	Wipe with dry soft cloth
Safety	Do not expose to moisture or extreme temperatures

Frequently Asked Questions - GR40 Fosi Audio

How do I pair the Fosi Audio GR40 with my phone?

To pair the GR40, turn it on by pressing the power button. The LED will flash blue. On your phone, enable Bluetooth and select 'Fosi Audio GR40' from the list. If prompted, enter PIN 0000.

Can I use the GR40 with multiple devices?

The GR40 can be paired with multiple devices, but it connects to only one at a time. To switch, disconnect from the current device and connect the new one.

What is the range of the Bluetooth connection?

The effective range is up to 33 feet (10 meters) in open line-of-sight. Walls and obstacles may reduce range.

How do I connect the GR40 to my stereo?

Use the included RCA cable to connect the GR40's L/R outputs to an available input on your stereo. Alternatively, use a 3.5mm aux cable if your stereo has an AUX input.

Why is there no sound from my speakers?

Check that the GR40 is properly connected to your stereo and powered on. Ensure your phone is connected via Bluetooth and playing audio. Also verify the stereo input source is correct.

Does the GR40 support aptX HD?

Yes, the GR40 supports aptX HD for high-quality audio streaming, as well as aptX, SBC, and AAC codecs.

Can I use the GR40 with a TV?

Yes, if your TV has analog audio outputs (RCA or 3.5mm), you can connect the GR40. However, note that the GR40 is a receiver, not a transmitter, so it will receive audio from a Bluetooth source like a phone, not send audio from the TV.

How do I reset the GR40?

To reset, press and hold the power button for about 10 seconds until the LED flashes red. The device will then restart and clear all paired devices.

What power source does the GR40 require?

The GR40 is powered via a Micro USB cable (included) with a 5V DC power adapter. Do not use a fast charger as it may cause issues.

Is the GR40 waterproof?

No, the GR40 is not waterproof. Keep it away from liquids and moisture to prevent damage.

USER MANUAL GR40 Fosi Audio

GR40 User Manual

Introduction

Thank you for purchasing the GR40 DAC Tube Preamp and Headphone Amplifier.

The GR40 is a powerful and well-designed preamp and headphone amplifier, integrating tube amplification with DAC functionality. It supports multiple input modes, including USB, optical, coaxial, and Bluetooth, making it compatible with a wide range of audio sources. The device features an input mode indicator for easy mode identification. Supporting DSD format with high resolution, it delivers a premium audio experience. The GR40 also includes a 3.5mm headphone jack, enhancing your desktop listening options for more convenient music enjoyment. The tubes are user-replaceable, and with the bass and treble knobs, you can customize sound effects, making your listening experience more diverse and personalized.

① 3.5mm Headphone Output

③ Bass Control

⑤ Power Switch/Mode Selector/Volume Control

⑥ Input Mode Indicator Light

⑧ 5654W Tubes

⑩ USB Input

⑫ Coaxial Input

⑭Bluetooth Antenna Connector

② DSD Indicator Light

④ Treble Control

⑦ Tube Decorative Rings

⑨ DC 12V Input

⑪ Optical Input

⑬ RCA Output

⑮ Bluetooth Reset Button

Specifications

Input Bluetooth, USB, Optical, Coaxial
Output	RCA, 3.5mm Headphone Output
Channel	2.0
SNR	≥103dB
Dynamic Range	104dB
Headphone Impedance	32Ω-300Ω
Headphone Outout Power	300mW@16Ω 250mW@32Ω50mW@250Ω 40mW@300Ω
Frequency Response	20Hz-20kHz(±1dB)
Sampling Rtae	32bit/384kHz; DSD256
Bluetooth Version	5.1
Bluetooth Connection Distance	≥10m
Bluetooth Transmission Format	SBC, AAC, aptX, aptX HD, aptX LL
Voltage Range	DC 12V

Package Contents

GR40

5654W Vacuum Tube*2

Decorative Ring*2 Power Adapter

Bluetooth Antenna User Manual

Operation Guide

1. Connect the Bluetooth antenna to the GR40;
2. Insert the 5654W tubes into the GR40, ensuring the pins are aligned, then attach the tube decorative rings;

3. Choose the appropriate cable (such as USB, optical, or coaxial) to connect the audio source to the GR40's audio input interface. Skip this step if using a Bluetooth audio source;

4. Use RCA cables to connect powered speakers. If using passive speakers, connect the preamp and power amplifier with RCA cables, then connect the speakers. If using headphones, connect them to the GR40's headphone output jack;

5. Power the GR40, press and hold the main knob for 3 seconds to turn on, then press once to switch to the desired input mode (connect to the Bluetooth now if using a Bluetooth device as the source), and set the volume to a low level.;

6. Play music, gradually adjust the volume to a suitable level, and use the bass and treble controls to fine-tune the sound to your preference.

Important Notes:

1. Since the GR40 is a tube preamplifier, please ensure to allow about 15 seconds for the tubes to warm up before playing audio;
2. The USB port is only for data transfer and cannot be used as a power connector;
3. Avoid plugging or unplugging cables while the device is powered on to prevent noise that could damage the product and impact your hearing.

Frequently Asked Questions

1. Bluetooth connection by others, what to do?

Long press the Bluetooth reset button for 3 seconds; the Bluetooth indicator will flash, and the GR40 will enter pairing mode. Simply re-pair your device.

2. Using a smartphone as a source in USB mode, why does sound only come from the phone even when connections are correct?

Check if the phone has data transfer enabled. Some models transfer data directly, while others require manual activation of this feature.

3. Can headphones and RCA outputs be used simultaneously?

The GR40 defaults to headphone priority output. To use RCA output, disconnect the headphones.

4. What are suitable tube models for replacement?

Tubes such as EF95, 6Ak5, 6AK5W, 403A/403B, 6J1, 6J1P, 6J2, 6J3, 6J4, 6J5 are compatible. You can test and choose according to your personal preference.

Note: When replacing tubes, ensure the GR40 is turned off and the tubes have cooled down to prevent burns or damage to the product.

If you have any further questions, please contact our support team at [e-mail].

Warranty and Maintenance

Fosi Audio pledges to give a 24-month limited warranty and support from the date of purchase. If you encounter any problem when using our product, please contact our support team at [e-mail].

About Us

Fosi Audio designs and builds innovative audio products with all your music in mind. Great sound, simple but elegant designs, high-quality components, and truly useful features are what Fosi Audio pursues. We sincerely hope you can get as much enjoyment from our products as we've had to create them!

Our Website: www.fosiaudio.com

Amazon Store: www.amazon.com/fosiaudio

Facebook Page: www.facebook.com/fosiaudioglobal

Youtube Channel: www.youtube.com/@fosiaudio

Official Forum: https://community.fosiaudio.com

Whatsapp: [phone]

After-Sales Service and Technical Support Email: [e-mail]

产品简介

GR40 5654W电子管 x2

电子管装饰圈 x2 电源适配器

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