Wednesday, June 19, 2013

Radial Engineering JDI Direct Box Review


I rained down praise upon the Radial Engineering Firefly direct box last month, but they have a lot of other great products in their line-up, including the JDI passive direct box.

Radial Engineering builds an impressive collection of products, including one of my direct boxes, 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 by running the board.

The Radial Engineering JDI is a bit more spendy than other simple direct boxes on the market, but it is 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, and it has a solid steel chassis, painted in a lovely green hue 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.

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 speaker switch is a second -30dB pad that can be used in with the -15dB input pad to allow the JDI to be connected in parallel with a speaker. This function includes a speaker emulation filter circuit. And lets the sound guy can tap the post-distortion signal, and

Unseen by human eyes, inside the JDI is a Jensen JT-DBE transformer, which is used as its main driver. The Jensen has magnetic memory, thus eliminating phase distortion. 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.

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.

As this is a passive device (no battery or phantom power required), the JDI is perfect for hot devices such as active or self-powered instruments, including acoustic guitars and basses with built-in battery-powered preamps, and AC-powered equipment such as drum machines, DJ mixers, and keyboards. These types of devices can overload active boxes, making them sound thin and shrill. The JDI can handle any of these things without distorting.

All of this quality and performance do not come cheaply. The Radial Engineering JDI passive 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!


1 comment:

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