JL Audio 300/4v2

Compact and dense four channel amplifier with cast Aluminium end panels and a cast Aluminium heatsink along one edge. All black powder coated with crackle finish. All connections are on one drop with controls and inputs gathered into two-channel clusters. Each channel pair gets a 50Hz to 500Hz crossover with a ten times multiplier switch. Although marked, the knobs are detented or go in notched steps and each is accurately rated as to frequency point. Tables in the back enable you to count detent notches as you rotate the controls and so calculate exactly the frequency point you wish. Optimised to offer steady power across a wide range of voltages and impedances, there are also tables in the manual to explain the optimum ranges for impedance of speaker loads to obtain full undistorted power. Very clean and professional-audio looking in appearance, it has neatly lined-up potentiometers with the panel holes (this is so rare!) and the switches all fit their gaps too. As well as gain and high/low level input switches, there is a 2ch or 4Ch input switch for use with a single set of line out RCAs and you get a switch to choose between 12dB per Octave Butterworth style crossovers, or 24dB per Octave Linkwitz-Riley 24dB slopes as well as the 1x or 10x multiplier switch.
– Class AB with Patented Absolute Symmetry„¢ dual N-Channel MOSFET output design
– 4 x 75w RMS stable from 1.5 to 4 Ohms (11 to 14.5V DC)
– 2 x 150w RMS stable from 3 to 8 Ohms (11 to 14.5V DC)
– Cast Aluminium heatsink and cast end caps with JL branding, brushed Aluminium top and front drop plates steel base
– 4Ga. Power Terminals with Allen headed grub screw bare wire socket connection
– 4Ch RCA input
– Adjustable input sensitivity in two switchable ranges: 200mV to 2V or 800mV to 8.0V
– Stereo & Mono operation
– Frequency response 5Hz to 30kHz (+0dB, -1dB)
– Signal to Noise Ratio >108.5dB
– Channel separation not quoted
– Power, Thermal and low impedance warning LEDS
– Crossovers, one per pair of channels, Highpass or Lowpass, switchable to either 12dB per Octave Butterworth or 24dB per Octave Linkwitz-Riley, 50Hz to 500Hz or x10 by multiplier switch for 500Hz to 5kHz
– Fuse Rating 40A x1 no internal fuse fitted but clear instructions are given in the manual
– HxWxD(mm) 58 x 235 x 340mm
Review by Adam Rayner
I was invited by the CEO of BBG, (JL Audio’s long term UK distributors) to the launch of the original ‘Slash’ amplifier range. Gordon knew that I would be perky enough to get the concept and ask corollary-based questions of the USA folks who came to tell us all about them that made it clear I got it too! I will admit that I do seem to get trotted out for foreign visitors to the various big Japanese companies as well from time to time, perhaps by way of reassuring their superiors that they know the folks in the press who know what they are on about. Either that or else I’m simply cheap as I don’t drink!
That was so long ago that the venue has since had a bypass of the A40 from its front door and gone bust and been demolished. (10 second’s silence for the Master Brewer I had some formative experiences in there.) However, the Big Idea remains and that is a real antithesis of the usual squeeze-it-for-all-the-watts-you-can approach. This is an amplifier that instead of dropping its guts into a low impedance will work across a range of them. It won’t do more watts into two Ohms and yet more into one, until its pips are squeaking. It’s optimised for a reliable amount of output across a slew of real world variations. The whole impedance issue can get a bit complex when you are looking to hook up different speaker arrays in variations of series, parallel and odd impedance combinations, so there are tables of hook up methods, with the best, or optimum ones, highlighted in bold print in the extensive manual.
Said manual is comprehensive and far better than the usual ‘Do not attempt to swallow whole or hit yourself on the head’ silly warnings and basic stuff that most sheets contain. I especially like the fact that the crossover controls may look like knobs (potentiometers) but they are actually precision detented controls that you can count clicks on and be certain that you have an accurately set crossover by frequency figure in Hertz instead of one that’s just about right.
It is a purist’s product and the v2 incarnation is definitely even better than the first. The crossovers can be set to run at 12dB or the far steeper 24dB per Octave slopes, which makes this one of the most comprehensively equipped of all eighteen amplifiers we tried in total. I also really liked the neat multiplier switches they use these in professional audio products and the concept works. In this case it means that the amplifier can accept a lower level signal than most and so will be able to wake up and do its best, even with a weedier input, although at the press of a button it can cope with signals from the hugest line driver in existence. The sheer precision with which the thing is put together reminded me powerfully of the function-breeding-form thing that so much professional equipment seems to exhibit but the sound was the thing that impressed me most.
It was large and powerful and again, seemed fast with those high rise time signals. Unlike most amplifiers which seem to change a little in sonic character as they are driven harder and harder, the deeply cunning power supply technology in this amplifier’s guts that enable it to cope with all the oddity of real world battery voltage fluctuations, also seems to function to feed the actual amplifier circuits with an even amount of oomph throughout. Thus as you wick it up, it just gets louder and doesn’t acquire any toughness or hardness. I fired up the trusty Talk Audio Anniversary edition (blue LEDs) AudioControl SA-3055 RTA/SPL meter to see how much wellie it could muster undistorted and it registered 124.3dB on the microphone.
My notes read, ‘really liked this one, just quality’ which does kind of say it all but the real ability is there in that audible high slew rate (the ability of an amplifier to raise huge signal change voltages rapidly and measured in volts per little bits of seconds) which makes for the rarity of that small ‘ting-ting!’ sound of a triangle or bell tree trill. A tiny bit better than the Tru Technologies Steel 44 but not quite as awesome as the DLS Ultimate A4, then, this is still a true audiophile’s delight and yet clever enough to cope with real world signal inputs and real world crap battery voltages.
It’s where pragmatic meets principled.
The JL Audio 300/4v2 scored well enough for it to garner a hard-to-win Talk Audio Recommended rating. It’s a damn fine piece of kit.
Overall 8.4
Sound Quality 9
Power Output 8
Features 9
Build Quality 10
Value For Money 9