Radial Engineering J48 Active Direct Box Review

Howdy!

I have reviewed the Radial Engineering Firefly and JDI direct boxes before and had nothing but praise for them, but they have a lot of other great products in their line-up, including the J48 active direct box.

Radial Engineering builds an impressive collection of products, including my favorite direct box, the aforementioned Firefly. Their stuff is comes dear, as they use quality components and their boxes are built with workers earning first-world wages in Canada.

First off – why would you need a direct box? If you want to send your instrument’s signal directly to the mixing board, a direct box will allow you to do this with a minimal increase in outside noise as well as reducing signal loss. It does this by converting a high impedance signal to a low impedance signal, as well as balancing this signal.

If the impedance is lowered, it will travel over long lengths of cable with less signal loss. Unfortunately, low impedance signals are more susceptible to noise created by magnetic fields – and just think of all of the magnetic fields created on stage by the amplifiers and lights. Old-school landline telephones also send low impedance signals over ridiculous lengths of wire with virtually no added noise. How do they do it?

They use balanced lines, which I am sure you have heard of if you have ever messed around with sound equipment. Balanced line split the signal into two equal parts, with one part in phase and the other part purposely inverted (out-of-phase). There is also a magnetic shield, which makes up the third pin of your standard XLR cable. Outside noise that passes through the shield is picked up equally by both wires. When the two signals come back together, the out of phase signal is brought back into phase along with the noise it has collected. The original signal is now in phase and the noise goes out of phase with its counterpart and cancels itself out.

So, a direct box (or DI box) takes care of all of this in one little component: It converts the high output impedance of the pickup to a low impedance signal and convert the unbalanced connection to a balance the line. Then you can plug it straight into a microphone line input and put your sound into the hands of the guy running the board. I hope you trust him…

This was all done with no added power, and a transformer was used to accomplish this task. Active DI boxes came out about 30 years ago because it was found that passive boxes did not work as well with high-output active basses, onboard preamps and keyboards. These units use batteries or phantom power (48V) without an expensive balancing transformer to provide the same results.

The Radial Engineering J48 active direct box is a bit more spendy than other simple direct boxes on the market, but it uses the phantom power to run a balancing transformer and has a military-grade printed circuit boards so that it ends up being a durable piece of equipment that works very well and should last for the rest of your career.

Looking at the unit, it is about the same size as an effect pedal (5 ½ x 3 x 2 1.2 inches), and it has a 14-gauge solid steel chassis painted in a lovely deep blue with neatly screen- printed graphics. It is shaped sort of like a hardcover book, so the steel wraps around and protects the switches from being torn off if you drop it or as it bangs around in your road case, There is a rubber pad on the bottom to help isolate it and to keep it from moving around.

The input panel has the usual 1/4-inch instrument input and traditional thru-put (to send your signal on to an amplifier). There is a merge switch that changes the thru-put jack into a second input, thus allowing a stereo signal to be summed into a mono signal. The instructions printed on top if the box, in case you forget how it is supposed to work. There is also a -15dB pad switch in case you have an exceptionally hot input, and an LED for the 48V phantom power check.

On the other side, the output panel has a balanced 600-ohm XLR connector with a hot pin 2 hot per AES specifications. There is a polarity reverse switch to toggle pin 2 and pin 3 to allow interface with older non-AES compliant equipment. The ground lift disconnects the pin 1 to allow for input and output isolation. The LOW CUT switch is an 80Hz high-pass filter that minimizes resonant feedback with acoustic instruments. This switch also headroom by eliminating unneeded bass frequencies.

In the real world, it does all of this exactly like it is supposed to. After you get it set up and plugged in you can forget it is there and get down to the business of making music. It is really nice to have a product that does exactly what the company says it will. It specs out with a 20Hz to 30kHz frequency range and it is quiet and perfectly isolated and with no added distortion you can count on your signal getting to the board just the way that you created it. You can use it to run straight into the board or into the snake with no fear of overloading the system.

I have tried it out with really high output basses (Alembic, Sadowsky, MusicMan Bongo, and Kubicki Factor) as well as a variety of keyboards and acoustic guitars with active preamps, and all of them worked spectacularly with the J48. They sounded exactly the same as they did when run directly into an amplifier, and I am completely hooked.

All of this quality and performance do not come cheaply. The Radial Engineering J48 active direct box has a list price of $220 and a street price of $199. It is worth every penny, and you should have one in your gig bag! Mahalo!