Radial J48 1-channel Active 48v Direct Box

Active 48-volt Phantom-powered Direct Box
Radial J48 1-channel Active 48v Direct Box image 1
Radial J48 1-channel Active 48v Direct Box image 1
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Radial J48 1-channel Active 48v Direct Box
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A Great-sounding Active Direct Box

Over the past quarter century, sound systems have evolved as have the instruments that are now used. The listener has also evolved. CD quality sound is no longer a luxury, but expected. Only now are we beginning to hear and appreciate the advantages of a good direct box. A good DI must provide a wide distortion-free frequency response and the dynamic range to handle today's powerful instruments.

Radial J48 at a Glance:
  • Active 48-Volt phantom powered direct box.
  • Minimal power draw with high rail voltage.
  • Will not choke when driven hard.
  • Low inter-modulation distortion.
  • Innovative merge function.
  • 80Hz highpass roll-off filter reduces mud and increases headroom.

The Radial J48 is an active direct box that has been specifically designed to work around the limited current that is available with 48-Volt phantom power, and do so while delivering the pure and natural sound of the instrument. A unique switch-mode supply steps up the internal rails to allow an input signal of up to 10V without any noticeable distortion.

Will Not Choke When Driven Hard

The single most important development goal of the Radial J48 was increasing the headroom without compromising sound quality. To this end, every possible effort was made to deploy the limited energy resources of phantom power to the audio signal path. To begin, phantom power is converted using a super-efficient digital switch-mode power supply that steps up the internal rail voltage to an impressive 10 volts. This allows one to hit the J48 with as much as 9-Volts without choking! To further increase available horsepower, all non-essential devices such a power-hungry LEDs are turned off when the J48 is in use. A typical LED requires almost as much current as does the complete audio circuit!

Lower Harmonic Distortion

Open up the Radial J48 and you will see huge, over-sized capacitors that provide ample current storage to assure clean, unobstructed power for the signal. With added headroom comes improved performance in all areas: Less than half the phase distortion of competing DIs, significantly lower harmonic distortion and single-digit inter-modulation distortion are all realized. Paying attention to these basic details has the net result of better sound.

Innovative Merge Function

But great sound is not the only innovation: The Radial J48 introduces several new functions that improve functionality and open the doors for greater creativity. The input panel features the usual 1/4" instrument input and thru-put connections. An innovative Merge function converts the thru-put into a second input to sum stereo sources to mono such as stereo keyboards or CD players when mixer input channels may be of short supply. A -15dB pad may also be inserted when confronted with abnormally high signals.

Reduced Hum and Increased Headroom

To reduce low-end rumble and run-away acoustic resonance, an 80Hz highpass roll-off filter is provided. As with any power system whether it is acoustic or electrical in nature, bass always contains significantly more 'RMS power' than high frequencies. This is why low-frequency drivers require anywhere from 10 to 20 times more power in PA system designs than high-frequency tweeters. By gently removing unnecessary lows, the J48's dynamic handling is increased by a full 3dB or twice the power handling. This innovative feature both reduces mud and increases headroom at the same time!

Like all Radial products, the J48 is built to handle the abuse on the road and features a unique welded I-beam construction for years of trouble free performance.

Radial J48 Features:
  • Welded I-beam construction makes it impossible to torque the PC board. This virtually eliminates cold solder joints - the No.1 cause of system failure in the field.
  • An innovative 'slide-in-place' XLR trace makes it possible to use I-Beam girder construction.
  • A digital switching power supply steps-up the internal rail voltage to 9-Volts. The J48 will not choke like other DI's when hit with large transients.
  • A military-grade PC board is employed for maximum wear and tear in abusive environments. Welded steel standoffs ensure the PC board will not shift.
  • A -15dB pad allows super hot inputs such as that from a CD player to be connected and balanced for long runs.
  • Momentary 48V Check LED will flash once when the 80Hz filter is depressed to tell you phantom power is present.
  • The Merge function turns the input & thru into 'left & right' inputs to mono mix at the XLR output. This handy function saves valuable inputs on the mixer!
  • The input is connected to the instrument.
  • The thru-put is connected to the instrument amplifier. The J48 has a high input impedance to reduce loading.
  • Our book-end design creates a protective zone around the switches & connectors for best protection!
  • A heavy-duty baked enamel finish for excellent durability and great looks for years! 100% 14-gauge steel construction.
  • The 600 Ohm balanced XLR out is mic level to properly match concert splitters - will drive 1000 feet without appreciable noise.
  • A polarity reverse switch flips the polarity from the AES standard Pin-2 to Pin-3 on the XLR and is used when combining sounds that may be out of phase.
  • An 80Hz low-cut (highpass) filter gently reduces excessive bass for more headroom and clarity. Eliminates run-away resonant feedback from acoustics!
  • The ground-lift disconnects the ground path to the transformer at the XLR output. This is used when a ground path is made at the input side such as with a keyboard.
  • A no-slip full bottom pad reduces mechanical vibration, improves electrical isolation and keeps the J48 from moving around on busy stages!
The Radial J48 is a great sounding active direct box!

Tech Specs

Type Active DI
Channels 1
Inputs 1 x 1/4"
Outputs 1 x XLR, 1 x 1/4" thru
Height 2"
Depth 5"
Width 3.3"
Weight 1.55 lbs.
Manufacturer Part Number R800 3001

Customer Reviews

Based on 10 reviews
Write your review

Believe the Hype..amazing for recording

I have a wonderful UA solo 610 running into an Antelope Zen Studio. Great sounds, but man, i've always had an issue with hum and buzz. I use some Collings Electrics (humbucker and P90 versions) but always had some hum. i tried this to help. I usually run my guitar into the Solo 610 and have the clean signal go into my Zen and then use the through on the Solo 610 go through effects into the Zen as a colored signal. I've never had luck with the through on the Solo, its loud, lots of hum and buzz. Even with ground lift..buzz/noise/static...too much I plugged the J48 in, used the through output and direct...hit the ground lift and wow, in all seriousness, i couldn't believe what happened. 100% noise gone. I have a furman power conditionar rack unit and it wasn't until i got the JDI (and the active DI as well for my guitar) that i really heard my gear sing. I use the J48 into my Solo610, its just insane how good it sounds now. The ground lift on the Solo never solved my issues, but this box did. I never really 'got' the whole thing about DI boxes, but this thing just solved so many issues. Sound quality of my pre-amps are dramatically improved. Believe the hype.

Wait, What?

Part of me wants to gush all about this J48, but here are the simple facts: I was using a cheap $20 DI box for my Taylor 618e (new version) with the Taylor Expression2 system, and I had to EQ the pants off the channel on our PreSonus StudioLive 32.4.2.AI desk at church (not name-dropping gear, just want to portray that I'm using decent components front to back). Then one of teh channels died so I started researching DI Boxes. This active J48 kept coming up as the winner for acoustic guitars rather than line-level keyboards (keyboards work fine but also do with a passive box). Seemed nuts to drop 200 bucks on a DI box, but when I saw that Tommy Emmanuel used to use this before switching to the line-out on the AER amp, I knew it was worth a try. Outcome: I now run the EQ F-L-A-T on the PreSonus board, and only slight cut the bass knob on the guitar, the treble knob stays flat also! I also leave the volume on the Taylor at center detent and just use the excellent XMAX pre in the board to get my signal in the mix. Unbelievable, I am so happy with the sound now, I thought the Taylor system was lousy, turns out my junky DI box was the issue. You can't rip this J48 out of my hands now, what a fool I was to think all DI boxes were the same. Final note: I do mostly fingerstyle and the Expression 2 system with a PRO DI box sounds very very good. Strumming can still be a bit boxy, but a slight cut around 300 should fix that. If you are using a rosewood acoustic then you'll need to cut more, this new maple Taylor is gorgeous in that respect, much less boxy tone. Nonetheless, if you have a pro instrument going to a pro system, a cheap DI is wasting your time. J48 all the way.

Absolute Life-Saver

I have always intended to re-amp my guitars so I can focus on getting a good take separately from worrying about microphone placement, etc. In doing so, I've been using the Radial X-Amp reamp box with a couple extremely nice preamps. I have a Great River and a Crane Song Syren in a 500 series lunchbox. Both have a "Hi-Z" input which I thought would be perfect on guitar. Both of these preamps are an absolute joy when a mic-level signal is used. However, using the Hi-Z input for a guitar is a nightmare. The headroom is practically nonexistent, causing them to distort very quickly unless the gain is set very low (the output from the pre not very hot as a result). And when you do leave enough space by keeping the signal from the guitar low, the reamped sound is thin and brittle sounding, the sound of the amp via the X-Amp and the guitar direct to amp absolutely night and day. In fact the DI on the 18i20 audio interface (no external pre in use) sounded better than the Hi-Z input on these $800+ preamps..! I bought this box praying it would solve the problem and it absolutely has. I now use the J48->whatever preamp and then reamp through the X-Amp. The result is that the reamped guitar signal sounds nearly identical to the guitar direct to amp, almost impossible to distinguish and definitely of a quality worth mic'ing. J48->Great River 500->X-Amp being my favorite signal chain, the thing works like an absolute dream and saved my reamping setup.

Radial J48 Review

When you need a road worthy, dependable, clean, interference resistant Direct Box, the Radial J48 hits the mark in every way. This box requires 48v phantom power, but it uses that circuitry to provide a strong clean signal all the way back to the mix station as well as feeding on-stage amplification an unaltered signal path. Pricey but worth every penny. I recommend. Steve D. DAWPRO Studios
Music background: Studio Owner/Operator/Engineer

The New Standard

Excellent DI for both recording and live. I do not like mentioning other names of products when comparing. But for all its worth the way this DI is built along with its capabilities its no wonder why this box isn't the industry standard.
Music background: Musician

Sweetwater Advice

Mark Magdich

The J48 Active Direct Box is absolutely amazing. I use it during a full-blown acoustic set with a 12-string. It's rich, has a lot of great output, and built like a tank (for all of you out there that know the kind of beating your gear takes when you are an active musician). Most of all, you can drive it to an extreme! Excellent choice and investment!

Dave Brow

This is THE DI to have! Excellent on bass, keyboards, and guitar. Get two, one for each ear!
See also: Direct Input Boxes, Radial, Radial Direct Boxes