638BCK - Hi-Fi System BOSS - Free user manual and instructions

Product Type	Digital Media Receiver (Car Stereo)
Model	638BCK
Brand	BOSS Audio Systems
Power Supply	DC 12V (negative ground)
Maximum Power Output	50W x 4 channels
Speaker Impedance	4 - 8 ohms
Fuse	15A blade fuse
Dimensions (W x H x D)	7.0 x 2.0 x 3.8 inches (178 x 51 x 97 mm)
Weight	1.54 lb (0.7 kg)
Radio Frequency Range (FM)	USA: 87.5 - 107.9 MHz; Europe: 87.5 - 108.0 MHz
Radio Frequency Range (AM)	USA: 530 - 1710 kHz; Europe: 522 - 1620 kHz
FM Channel Step	USA: 200 kHz; Europe: 50 kHz
AM Channel Step	USA: 10 kHz; Europe: 9 kHz
Bluetooth Profiles	A2DP, AVRCP, HSP, HFP
Bluetooth Range	Up to 30 feet (10 meters)
Supported Audio Formats	MP3, WMA
Media Sources	USB, SD Card, AUX, Bluetooth Streaming, Radio
Preamp Outputs	Front and Rear (RCA pairs)
Frequency Response	20 Hz - 20 kHz
Signal-to-Noise Ratio	60 dB
Audio Output Impedance	4 ohms (speakers)
Preset Memory Stations	30 (6 each for FM1, FM2, FM3, AM1, AM2)
Display	LCD with backlight
Controls	Rotary volume, buttons for source, tuning, preset, mute, etc.
Remote Control	Included (IR)
Detachable Faceplate	Yes
Safety Warnings	Use only with 12V negative ground; replace fuse with same rating; do not disassemble
Maintenance	Clean with soft dry cloth; avoid liquids

Frequently Asked Questions - 638BCK BOSS

How do I pair my phone via Bluetooth?

Ensure the unit is on and the Bluetooth logo is flashing. On your phone, enable Bluetooth and select 'BOSS AUDIO' from the list. Confirm pairing; the logo will stop flashing. Once paired, audio will transfer automatically.

How do I reset the unit to factory defaults?

Use a pointed object (like a pen) to press the RESET button on the front panel. This clears all settings, including presets and Bluetooth pairings.

How do I set the clock?

Press and hold the CLK button until the time flashes. Use the >>| or |<< button to adjust hours and minutes. Press CLK again to save.

Why is there no sound from the speakers?

Check that the unit is powered on and the volume is not muted. Ensure the car ignition is in ACC or ON position. Verify speaker connections and that the fuse is not blown.

How do I store radio presets?

Tune to the desired station. Press and hold one of the preset buttons (1-6) for more than 2 seconds. The station is stored. Repeat for other stations. You have 5 bands (FM1, FM2, FM3, AM1, AM2) each with 6 presets.

Can I play music from a USB flash drive?

Yes, insert a USB flash drive with MP3 or WMA files into the USB port. The unit will automatically switch to USB mode and start playback.

How do I switch between radio and Bluetooth audio?

Press the SRC button repeatedly to cycle through sources: Radio, Bluetooth, USB, SD Card, AUX. Select Bluetooth to stream music from a paired phone.

What should I do if the remote control stops working?

Replace the lithium battery (CR2025 or similar) inside the remote. Ensure there is no obstruction between the remote and the unit's IR sensor. Reset the unit if needed.

How do I adjust the balance and fader?

Press the volume knob repeatedly until 'BAL' appears, then turn the knob to adjust left/right balance. Press again for 'FAD' to adjust front/rear fader. Press and hold to exit.

Is it safe to install the unit myself?

If you have basic car audio installation experience, you can install it. Ensure the car battery is disconnected first. Follow the wiring diagram carefully. For best results, have a professional install it.

USER MANUAL 638BCK BOSS

Precautions....1

Lithium Battery Cell Warnings 1

Take Precaution....1

Installation 2-3

Installation Procedures 2

Installation Opening....2

Wiring Connections....3

Remove of the Main Unit 3

Control Panel Button Locations....4

Operation 4-5

Power / SRC 4

Adjust Menu Options (SRC) 4

Change the Source (SRC) 4

Store/Recall Preset Stations-(1..6) 4

Play/Pause 4

Next/Previous Track....4

Fast Forward/Backward 4

Set the Clock (CLK) 4

Insert SD Card 4

Insert USB 4

Adjust Volume (VOL) 5

Switch Between US and EU Frequency 5

Manual Tuning·(|<<./>>|) 5

Auto Seek Tuning (|<< / >>|) 5

Change Bands (BAND) 5

Automatic Music Search (AMS) 5

Track Search 5

Track/Folder Navigation 5

Mute 5

AUX In Jack 5

Reset System (RESET) 5

Bluetooth Operation....6

Pair and Connect 6

Make a Call 6

Redial Last Dialed Number 6

Answer a Call....6

End a Call 6

Switch Audio Between Car and Phone 6

Adjust Talk Volume....6

Audio Streaming (A2DP)....6

Troubleshooting....7

Specifications 8

Lithium Battery Cell Warnings

• Cell leakage may cause damage to the remote control.
• Do not throw cells into fire, as this may cause an explosion.
- Keep battery cells out of reach of children.

Take Precaution

• To reduce the risk of fire, electric shock, and annoying interference, do not repair yourself. Please refer serving to qualified person.
• Some MP3/WMA files may not be playable.
- Keep lower volumes to concentrate on traffic and road conditions.
• If the battery is disconnected or discharged or changed, the preset memory will be erased and must be reprogrammed.
• Installation of unit is better at a horizontal position, or if it is at an angle, it may be not working at its best situation.
- Be sure to lower the volume before switching off the unit or the ignition key.

Installation Procedures

First complete the electrical connections and then check for correctness.

Installation Opening

This unit can be installed in any dashboard. Having an opening as shown above.

Insert mounting collar into the dashboard and bend the mounting tabs out with a screwdriver.

Make sure that lock lever(※) is flush with the mounting collar (not projecting outward).

Pure technical line drawing of a mechanical component inside a housing (no text or symbols)

• Only use speakers with 4 ohms impedance.
• Do not attach the control panel to the chassis before wiring is complete.
• The maximum current of the auto antenna is 200mA.

Wiring Connections

Removal of the Main Unit

1. Remove the metal strap from the main unit.
2. Remove the plastic trim out from the main unit.
3. Insert a bracket key into the left and right side of the main unit and draw the unit out of the mounting sleeve.

OPERATION

1. POWER/SRC

Press the POWER button to turn on the unit, and long press it again to turn off the unit.

When the unit turn on, short press POWER/SRC button to switch the unit between

RADIO, BT, USB & CARD, AUX IN, modes (if there are USB and SD card inside the unit).

1/. If there is no USB & SD card, then it will be only radio and Aux. When the user

inserts a USB flash drive or SD Card, their respective logos will illuminate on the display.

2-7.(button 1 to 6) PRESET MEMORY BUTTONS In Radio mode

To memorize the frequency, press one of the six preset buttons(1-6) hold for more 2"S, the frequency is successfully stored.

Therefore there are FM1, FM2, FM3, AM1 & AM2, each band can store 6 stations, so total 30 stations can be stored.

To recall the preset memory station, press one of the preset buttons(1-6) plus the BND button for FM1, FM2, FM3. AM1 & AM2.

During USB or SD card mode, press '5/-10' button to go backward 10 tracks.

Press '6/+10' button to jump forward 10 tracks.

During USB or SD card mode, long press '5/-10' button to go back 1 folder.

Long press '6/+10' button to go up 1 folder. You can repeat this function depending on the number of folders. This button will have no function if the USB or SD card has no folders.

8. CLK

Press the CLK button once to display the real time, With time appearing on the display. Press and hold CLK button for more than 2 seconds until the time flashes. You can adjust the HOUR and MINUTE by pressing the >>1 button and 1<< button respectively and press the CLK button to switch the HOUR and MINUTE.

9. USB Port / Micro SD Card Slot

10. VOLUME adjustment

In the radio mode, rotate the volume knob to increase or decrease the volume level of the sound output. Press the volume knob, it will be switching the sequence as follows:

graph LR
    A["Bass"] --> B["Treble"]
    B --> C["Balance"]
    C --> D["Fader"]
    D --> E["EQ off"]
    E --> F["Loc Loud Stereo Vol"]

In the USB or SD card mode, press the volume knob to enter the EQ function that the audio mode in the following order: EQ OFF → FLAT → POP → ROCK → CLASS

At the radio status, press and hold the VOL button to enter switch state of the US(USA) and EU (EUROPE) frequency, then rotate the VOL knob to select US frequency or EU frequency, after selecting US or EU frequency, the system will switch to the selected frequency 3 seconds later.

11.FF(>>|) &12.FB(|<<)

In the radio mode, long press the FF(>>1) or FB(1<<) button for more than 2 seconds, the unit will search the next or previous frequency step by step.

Short press the FF(>>1) or FB(1<<) button, the automatic search will start, it will search upward or downward for the strong signal radio station within the cuttent band. The auto searching will stop until find a station.

13.BND/AMS

In radio mode, short press the BND/AMS button repeatedly to select the one of the radio band: FM 1, FM 2, FM 3, AM1, AM2 in a cycle sequence. When you select a band, the word F1、F2、F3 for FM band, and A1、A2 for AM band will be shown on the LCD display. Press the BND/AMS button for several seconds, the radio searches form the current frequency and check Whening Strength stations will search is finished. stored into the corresponding preset number within the current band. Short press the BND/AMS button to scan each preset station in each band.

14. MUTE

Short press the MUTE button to turn MUTE ON/OFF, when it is on, the MUTE will be flash on the LCD and no sound output. When short press again it will be cancelled.

15. AUX IN JACK

16. RESET

To reset all parameters to factory default values. Use a subject with a sharp point end to thrush the RESET hole.

Pair and Connect

Prior to using the Bluetooth device as a handsfree system for a Bluetooth-enabled mobile phone for the first time, you must pair and connect the two devices as follows:

1. In any mode, prior to pairing and connecting, the BT logo flashes in the LCD indicating that no device is connected. To begin pairing, enable BT mode on your mobile phone.
2. When the phone finds the car audio system, the BOSS AUDIO name will be displayed.
3. Choose the BOSS AUDIO from the device list to pair and connect with the car audio system. Upon confirming, the BT logo will stop flashing.
4. When pairing is complete, the mobile phone audio will automatically transfer to the car audio system whenever a call is made or received, or when the mobile phone plays music.

Make a Call

To make a call, dial the call directly from the paired mobile phone.

Redial Last Dialed Number

Press and hold the button on the control panel to redial the last dialed phone number.

Answer a Call

• When the mobile phone is called, the incoming telephone number displays in the LCD.
• To receive the call, press the button on the control panel.
• To reject the call, press the button on the control panel.

End a Call

To end an active call, press the button.

Switch Audio Between Car and Phone

During a call, press the VOL knob/button to switch the audio source from the car audio system back to your mobile phone.

Adjust Talk Volume

• During a call, use VOL knob or VOL + and VOL - buttons to adjust the volume level.
- Use the MUTE button to mute sound.

Audio Streaming (A2DP)

1. Press the /SRC button to enter BT mode and display media in the LCD.
2. When a mobile device is paired, music played through that device will automatically be heard through the car audio system.
3. Press the >>| or |<< button to play the next or previous song/file on the mobile phone.
4. Press the >|| button to pause or resume music playback.

If you suspect something is wrong immediately switch power off. Do not use the unit in abnormal condition, for example without sound, or with smoke or foul smell, can cause fire or electric shock. Immediately stop using it and call the store where you purchased it. Never try to repair the unit yourself because it is dangerous to do so.

graph TD
    A["General"] --> B["No power or no sound"]
    B --> C["Car's engine switch is not on. Turn your car's key to ACC or ON.<br>Cable is not correctly connected. Check connection.<br>Fuse is burnt. Replace fuse. Check volume or mute on/off."]
    D["Radio"] --> E["A lot of static in broadcast"]
    E --> F["Station or signal is too weak.<br>Select other stations of stronger signal level."]
    G["Preset station is reset"] --> H["Battery cable is not correctly connected.<br>Connect the battery cable to the terminal that is always live."]
    I["USB / SD"] --> J["USB or SD card is connecting but No Sound"]
    J --> K["USB or SD card connection is not good.<br>Take it out and insert again.<br>USB or SD card is damaged or no music file inside.<br>Change to another USB or SD card, or record music inside it."]

General

Power supply Requirement : DC 12V

Maximum power output : 50W X 4CH

Speaker impedance : 4 - 8 Ohm

Unit Dimensions(WxHxD) : 7.0 X 2.0 X 3.8 inch

Weight : 1.54 Lb (0.7 kg)

Fuse : 15 A

RADIO

FM

Frequency Range USA / EUROPE: 87.5 MHz - 107.9 MHz / 87.5 MHz - 108.0MHz

Channel step: 200 KHz / 50 KHz

AM

Frequency Range USA / EUROPE: 530 KHz - 1710 KHz / 522-1620 KHz

Channel step: 10 KHz / 9 KHz

USB/Card

Usable Audio Formats.... MP3/WMA

Pre-amp Output.... Front and Rear

Frequency Response 20 Hz - 20 KHz

S/N Ratio 60dB

BT

BT Profile supports.... A2DP, AVRCP,HSP & HFP profiles

Range of frequency.... 2.4GHz spectrum

USER'S MANUAL

611UAB

BLUETOOTH®-ENABLED | MP3-COMPATIBLE DIGITAL MEDIA AM/FM RECEIVER

BOSS®

AUDIO SYSTEMS

BOSS Audio Systems

3451 Lunar Court • Oxnard, CA 93030

www.bossaudio.com | 805.751.4853

tech support: www.bossaudio.com/support

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