PJB BG-80 Double Four Plus Combo Amplifier Owner’s Manual

: June 1, 2024
: PJB

Table of Contents

PJB BG-80 Double Four Plus Combo Amplifier
Product Information
READ THIS FIRST
OVERVIEW OF THE DOUBLE FOUR PLUS
PANEL OVERVIEW
OPERATION & POSITIONING
TRANSPORTING AND STORING THE DOUBLE FOUE PLUS
SPECIFICATIONS
SERVICE/WARRANTY INFORMATION
Contact
References
Read User Manual Online (PDF format)
Download This Manual (PDF format)

PJB BG-80 Double Four Plus Combo Amplifier

PJB-BG-80-Double-Four-Plus-Combo-Amplifier-product

Product Information

Specifications

Model: DOUBLE FOUR PLUS (BG-80)
Type: Combo Amplifier
Input Jacks: Auxiliary Input, Instrument Input
Controls: Auxiliary Input Level, Bluetooth Input Level, Mute/Active/Passive Selector, Level Input Control, Bass/Mid/High EQ Controls, Master Volume Control, Line Out Control
Output: Line Out, Headphone Jack
Power: DC IN 20V

Frequently Asked Questions

Q: How do I connect my instrument to the amplifier?
- A: Use the Instrument Input Jack to connect your passive or active instrument.
Q: Can I use Bluetooth devices with this amplifier?
- A: Yes, you can connect Bluetooth-enabled devices by adjusting the Bluetooth input level and following pairing instructions.
Q: How do I optimize the sound quality through headphones?
- A: Use high-quality stereo headphones with the Headphone Jack for the best sound experience.

Thank you for purchasing the PJB DOUBLE FOUR PLUS BG-80. A great deal of dedication and passion went into designing and building this no-compromise, high performance combo amplifier. It was conceived to be a dedicated amplifier for the “connoisseur” bassist. Reading and following this manual will enable you to get the best performance from the amp and ensure its longevity.

READ THIS FIRST

Before using the DOUBLE FOUR PLUS, please read ALL the instructions.
On receipt of product, check for any signs of physical damage arising from shipping. If any damage is visible, contact your retailer.
Do not install this equipment in a conﬁned or building-in space such as a bookcase or similar unit. The amp should remain in well ventilation conditions at an open site. The ventilation should not be impeded by covering the ventilation openings with items such as newspaper, tablecloths, curtains, etc.
WARNING: Only use attachments/accessories speciﬁed or provided by the manufacturer.
WARNING: To reduce the risk of ﬁre or electric shock, do not expose the amp to rain or moisture. The amp shall not be exposed to dripping or splashing. Objects ﬁlled with liquids such as a coﬀee cup shall not be placed on top of the amp.
When not in use and during movement, please take care of the power cord, e.g. tie up the power cord with cable tie. It shall be free from sharp edges which can cause abrasion of the power cord. When put into use again, please make sure the power cord being not damaged. If any damages found, please replace it with one s peciﬁed by the manufacturer or with the same speciﬁcations as the original one.
Correct Disposal of this product. This marking indicates that this product should not be disposed with other household wastes throughout the EU. To prevent possible harm to the environment or human health from uncontrolled waste disposal, recycle it responsibly to promote the sustainable reuse of material resources. To return your used device,please use the return and collection systems or contact the retailer where the product was purchased. They can take this product for environmental safe recycling.

OVERVIEW OF THE DOUBLE FOUR PLUS

The DOUBLE FOUR PLUS is a single channel bass amplifier that has an auxiliary input for iPad/iPod, smart phone or drum machine. It features 3 band EQ that is perfectly tailored for bass guitar, a stereo headphone out jack and a line out for recording, it can also play music with the Bluetooth(V5.1 with Qualcomm® aptX™ HD) function. It is ideal for all kinds of basses, and can handle the open B string on a 5-string bass with ease.

The Enclosure

It is well known that big speakers are capable of reproducing true fundamental bass frequencies. But as you decrease the physical size of a speaker, the bass response will fade away. This is the reason why
Violins are small and Double Basses are big!

So how do you get a big bass sound from a small speaker cabinet? With our know-how of using smaller drivers to get the ultimate bass sound, we applied our vast experience to an even smaller driver which is just 4 inches across. Built with Swiss watch precision, it can cope with the extreme signals from an amplified bass guitar. Using our extensive R&D facilities which include the largest anechoic chamber in the bass guitar amplifier industry and the KLIPPEL transducer measurement system (it uses lasers!), we were able to develop the perfect 4-inch loudspeaker. We analyzed the cone behavior at all frequencies in 3D representation, cone suspension and frame, etc. until we achieved a transducer beyond what anyone would have ever thought possible. Then we looked at the acoustic loading using the acoustic simulation software and calculated the total power cone displacement at every frequency.

We designed a custom Rectangular Auxiliary Low Frequency Radiator (RALFR®). That is a pneumatically coupled radiator loaded to the rear of the two 4-inch speakers that operates at the lowest bass frequency only. It augments the output of the loudspeakers at frequencies from 30 to 150 Hz. It also reduces the cone excursion of the speakers, allowing greater power handling. The proprietary PJB “long-throw” 4-inch speakers have a full frequency range to the highest audio frequencies. Not only does this give greater clarity and transparency to your instrument, but also a high-fidelity sound to any backing track fed into the auxiliary input. The cabinet may be as small as a shoe box, but it is built to the same high quality as all PJB cabinets, What you hear from the DOUBLE FOUR PLUS is the closest to the original sound of the instrument. The sound is huge for its size and it is unbelievable that all the sound from your bass is just coming out of such a tiny jewel.

AMPLIFIER FEATURES

Digital Amplifier with 90Watts (2x45W) 1% THD
Switchable high gain input OR low gain stage with mute function
Independent level control and mute function to both Aux and Bluetooth input
One stereo input for Drum machines or iPod/Smartphone players
3-Band EQ
Line Output for recording or driving another amplifier
Bluetooth 5.1 with Qualcomm® aptX™ HD codec
Use under any AC voltage worldwide. (90~240V)
DC input (USB Type-C port) connection supports Portable charger of USB PD (Power Delivery) Protocol.

PANEL OVERVIEW

PJB-BG-80-Double-Four-Plus-Combo-Amplifier-fig-2

Auxiliary Input Jack(3.5mm stereo)
- This is a stereo mini jack that can receive any signal from iPod, iPad, smart phones or drum machines.
Auxiliary Input Level
- Rotate: increase or decrease the AUX input level.
- Press: mute/unmute AUX input.
Auxiliary Mode Indicator
- Orange light steady lit: AUX input is mute.
- Light oﬀ: normal playing state.
Bluetooth Input Level
- Rotate: increase or decrease the Bluetooth input level.
- Press: mute/unmute Bluetooth input.
- Press and hold: disconnect Bluetooth.
Bluetooth Mode Indicator
- Blue light ﬂashes: wait for pairing.
- Blue light steady lit: connected.
- Orange light steady lit: Bluetooth input is mute.
Instrument Input Jack
- This is a high-impedance input and is designed for all passive and active instruments.
Mute/ Active/ Passive selector switch
- Mute: mute the input stage; when switched on, the clip LED will light up in green.
- Low: lower sensitivity input setting for guitars with onboard electronics.
- High: higher sensitivity and high impedance input for passive guitars.
Clip Light
- When the power ampliﬁer is overloaded and causes distortion, the clip light will light up in red. When the ampliﬁer is mute, the LED will light up in yellow.
Level Input Control
- The signal size of the input level will be aﬀected by diﬀerent instruments, players and playing styles. And the input level can be adjusted to avoid the overload indicator from lighting up during the vigorous playing. This optimizes the best signal-to-noise ratio between AMP and instrument and will give you the full extent of the ampliﬁers’ tone and power.
Bass EQ Control
- Boosting or cutting this will have a signiﬁcant eﬀect on the tone.
Mid EQ Control
- Boosting or cutting mid-range.
High EQ Control
- Boosting or cutting treble.
Master Volume Control
- This controls the volume of Speakers and Headphone output.
Headphone Jack
- You can use all kinds of stereo headphones through this jack but you will only hear good sound if your headphones are high-quality.
Line Out Control
- Adjust the output signal for Line Out.
Line Out
- It can be used for driving a second ampliﬁer or loudspeaker.
Power Switch
- Blue light steady lit: power on.
1. Note: For Safety, we advise you to unplug the power supply from the AC power if you do not intend to use the DOUBLE FOUR PLUS for long periods.
2. Before switching on the product, set the VOLUME, LEVEL, LINE OUT VOL. to the minimum.
Power Indicator
- Blue light ﬂashes: although it is connected successfully to a PD protocol, the power is not turned on.
- Blue light steady lit: it is successfully connected to an AC power and power is turned on.
Type-C Port
DC input (USB Type-C port) connection supports Portable charger of USB PD (Power Delivery) Protocol.
This port is only used for power input but not for power supply.
Supports USB PD Protocol (20V/3A and above)
After it is successfully connected to a PD Portable charger, the power indicator will ﬂash during the shutdown. The product is ready for use.
When the power of the Portable charger is lower than 10%, it may cause the sound to cut oﬀ or be intermi?ed.
The maximum power output of the power source and speakers:
DC 20V/3A/Speaker: 2×25W Max.
DC 20V/5A/Speaker: 2×40W Max.
The discharge time when using the power bank via Type-C (for reference):

  * About 8 hours continue working with a 20000mAh power bank output 20V/3A.
  * About 5 hours continue working with a 20000mAh power bank output 20V/5A.

AC Input Socket
- Connect to your AC power . (90~240V)
- Connect to a grounded outlet in accordance with the input power voltage and frequency speciﬁed below the power inlet.

OPERATION & POSITIONING

TURN THE VOLUME DOWN on the DOUBLE FOUR PLUS before plugging in your instrument. You may notice the clip light blinks once on turn on. This is normal and the ampliﬁer is operating correctly. It is just a character of the circuit.

Positioning the DOUBLE FOUR PLUS for Best Sound

Generally, playing in diﬀerent venues will cause your bass to sound diﬀerently. This is partially due to the acoustics of the hall inﬂuencing the low-frequency waves that are coming from your speaker. Bass waves are large and room dimensions heavily inﬂuence them when the walls reﬂect the sound waves, causing them to collide by adding together or canceling each other out. This causes some fundamental notes (the ones you feel more than hear) to ring out louder than others and some notes not to be heard at all.

Below is an indication of what fundamental bass frequencies are, showing open string’s approximate frequencies and acoustic wavelength:

B string / 31Hz / 36 feet
E string / 41Hz / 27 feet
A string / 55Hz / 20 feet
D string / 73Hz / 15 feet
G string / 98Hz / 11 feet
C string / 130Hz / 9 feet

This may give you some indication of the offending notes (frequencies) that may be booming or resonating louder or quieter than others. For example, if your speakers are five feet away from the wall, the open A string may sound weak. That could be because the path length of the reflected sound off the wall from your speaker is exactly corresponding to half a wavelength on the open A string causing that particular note to cancel out.

The position where the DOUBLE FOUR PLUS is placed will ultimately affect your low-frequency limit. For best results, place the DOUBLE FOUR PLUS on the floor. Placing it on objects off the floor will cause it to sound thin and lack bass punch. Placing the DOUBLE FOUR PLUS next to a wall will reinforce the lower notes. Placing it in a room corner will further enhance the low notes. Room size makes a big difference in how deep the bass will sound. The further the distance to the listener the weaker the bass will be. This is due to the physics of acoustics not the unit itself.

Unfortunately for bass players, low frequencies are always very difficult to control with room acoustics. The reproduced wavelengths of the notes you are playing often correspond to the room dimensions, in which case the reflected sound off the walls interferes with the sound from the speaker as you get further away from it.

Getting the most from your DOUBLE FOUR PLUS

It is important to understand this is a quite different amplifier from the conventional analog amp. The controls transmit information to two internal microcomputers: one for the pre-amp and the other for the power amp.

This information is processed as EQ changes or level changes, so it takes a short time for the computers to act on changes to EQ and volume controls. This is known as latency and if you change control while playing simultaneously, you will notice a low delay as the changes are processed. It is simply the character of the processor and not the fault of the unit.

All amplifiers will be affected by the room they are in and it can make a huge difference to the sound where you place your amplifier. If you place the amp on a table far from any wall, this will give you the least bass (low frequency) output. Walls, Floors and Ceilings work like a mirror to the amplifier because the sound wave is reflected and it will magnify the sound. So placing the unit on a floor and close to a room corner will give you the most bass output. You should experiment to choose the best placement for the optimal sound.

Speakers are a bit like shoes, new ones are never as comfortable as old ones and in time speakers will “soften” up. The sound will become warmer and fuller in time and it’s required to play for a break-in period to get the amp to perform its best. This can also be done just by playing music through the AUX input instead of playing.

TRANSPORTING AND STORING THE DOUBLE FOUE PLUS

When transporting in a vehicle, it is recommended that you use an external case or heavy-duty cover to prevent it from being damaged by falling over or other objects falling on it.

Storing:

Keep in a dry location preferably at room temperature.
Do not store in temperatures below -20℃or above 40℃.
Do not allow it to get wet. If this occurs, never turn it on in this condition.
Do not leave the DOUBLE FOUR PLUS permanently connected to a power source.

SPECIFICATIONS

Amplifier

Amplifier Type: Full Digital with DSP
Power Output: 90 Watts(2x45W) 1% THD
Signal to Noise Ratio: ≥85dB（A）（EQ off, Volume on Full）

Impedance

Input: ≥270KΩ / 22pF

Speaker

2×PJB 4-inch Full Range Speaker
1× Rectangular Auxiliary Low Frequency Radiator.
Usable Frequency Response: 40Hz to 17KHz

Levels

Hight Input: 120mV-2 V
Low Input: 400mV-3V
Aux Input: 200mV (MAX)
Bluetooth Input: 300mFFS

EQ Center Frequencies

Bass Shelf 100Hz, +/- 15dB
Mid 1KHz Bandwidth 120Hz-10Kz, +/- 15dB
Treble Shelf 10KHz, +/- 15dB

Included Parts

6ft AC Power Cord, 5.5ft Audio Cord.
Dimensions (W×H×D): 13×8×8.5 inch (329×203×215 mm)
Weight: 11.3 lbs / 5.1kg

SERVICE/WARRANTY INFORMATION

The DOUBLE FOUR PLUS carries a 2-year limited warranty on parts and labor. Products must be purchased from an authorized PJB dealer.
Buyer must complete and return the enclosed warranty card within 15 days of purchase, or register online by www.pjbworld.com.

This warranty covers defect in materials or workmanship that occurs in normal use. Within warranty period PJB or its local distributor will repair or replace the defect unit free of labor and parts charge. It is the buyer’s responsibility to use the unit strictly according to instructions writtien in the owner’s manual. This warranty is not transferable; it is provided to original owner only.

Damage /defects caused by the following conditions are not covered by this warranty:

Improper handling, neglect or failure to operate the unit in compliance with the instructions given in user manual.
Connection or operation in any way that does not comply with the technical or safely regulations applicable in the country where the product is used.
Speakers are not covered for damages caused by incorrect connection, or when powered beyond the limit described in the user manual. Manufacturing defects are typically detected during early usage.
Repairs or modificafions by anyone other than authorized PJB service agent.
Damages/defects caused by force majeure or any other condifion that is beyond the control of PJB.

IMPORTANT:

In all warranty issues your first line of communication should be to the retailer you purchased from, even if you have purchased product from an online source.
When a local distributor is available, customer who prefers to purchase across country online maybe required to pay shipping charges to retailer in order to obtain service.

Warranty policies differ in countries outside of USA. Please check with local distributors for warranty information in your region. Register first with your local distributor if available will give you better and quicker service when needed.

For further questions, please contact your local distributors, or PJB by email info@philjonespuresound.com.