Phil Jones is a professional audio engineer and bass player who has been in business for over 4 decades now. He noticed that traditional bass amplifiers were built on old principles but these were not really effective. Being a world class HiFi speaker designer himself, he started PJB with the intention of applying the same technology and design that was used in that exclusive HiFi speaker world to produce bass amps that would be effective, affordable and reliable.
From the beginning, PJB's most innovative feature was the use of small speakers proving that, if done right, these are far more effective than larger ones. Of course a lot of research went into this and multiple tests were performed to check the beaviour of the speakers, the use of PWM amplifiers and specially designed cabinets.
All PJB amps produce a clear and undistorted sound as well as a very deep and focused low end that is usually hard to belive it comes form such a small amp.
This is the DOUBLE FOUR combo and here's the description by PJB themselves:
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The DOUBLE FOUR is the pinnacle of micro bass amps. With new driver design, acoustic loading and the latest digital amplifier technology, this tiny bass combo may be designed as a practice amp but continues to amaze everyone with the great PJB signature bass tone. From a cabinet with size of a jewel box, this seems to defy the laws of physics.
- Driver and Amplifier Technologies
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Driver and Amplifier Technologies Pushing our expertise of using smaller drivers to get the ultimate bass sound, we applied our vast experience to an even smaller, “Neo Power”4 inch driver built with precision of a Swiss watch. This 4” baby is able to cope with the extreme signals coming in from an amplified bass guitar. By using our extensive R&D facility which includes the largest anechoic chamber in the bass guitar amplifier industry, and the KLIPPEL transducer measurement system, we were able to develop the perfect 4 inch transducer for our purpose. We analyzed the neodymium magnetic system, the cone behaviors at all frequencies in 3D representation, cone suspension and frame, until we achieved our goal. We then looked at the acoustic loading using the acoustic simulation software and calculated exactly the full power cone displacement at every frequency.
Each one of these 4” speaker is fed with its own Pulse Width Modulation PWM amplifier. PWM amplifiers are extremely efficient compared to the traditional analog solid state amplifiers, converting electrical energy to power using on the speakers instead of wasting it on hot. Since the amp is running at lower working temperature, the DOUBLE FOUR will give years of service long after other amps have faded away. By using dual amplifiers one for each speaker, the bass control is greatly improved since the damping factor ( the amplifier’s ability to put on the “brakes” to stop the speaker cone from overshoot ) is doubled. The end result? A bass tone that is well controlled, punchy, tight and never muddy or bloomy.
- Enclosure Technology
- To maximize its tiny cabinet enclosure, we designed a custom Rectangular Auxiliary Low Frequency Radiator (RALFR®). RALFR® is a pneumatically coupled radiator loaded to the rear of the two 4 inch speakers that operates at the lowest bass frequencies only. It augments the output of the loudspeakers at frequencies from 30 to 150 Hz. It also reduces the cone excursion of the speakers, so power handling is greatly improved. The cabinet is also heavily braced internally and lined with acoustic damping materials. This damping prevents cabinet coloration that can interfere with the true sound of your instrument. Now, what you hear from the DOUBLE FOUR is the most realistic amplification of your instrument.