Radial ProDI 1-channel Passive Instrument Direct Box

Passive Mono Direct Box with Custom Transformer and Rugged I-beam Construction
Radial ProDI 1-channel Passive Instrument Direct Box image 1
Radial ProDI 1-channel Passive Instrument Direct Box image 1
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Radial ProDI 1-channel Passive Instrument Direct Box
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High-quality Direct Box from Radial!

The Radial ProDI is a high-quality, passive mono direct box that's perfect for use with acoustic guitars, bass guitars, electric pianos, and synthesizers. The ProDI's custom transformer helps to deliver the highest performance possible, virtually eliminating issues with noise. And, as with all Radial DI boxes, the ProDI is incredibly reliable and easy to use — just plug in your mono instrument and instantly eliminate ground loops, while enjoying a rich, full sound. If you need the same excellent quality in a stereo version, Radial also offers the ProD2 stereo version.

Raidal ProDI Passive Mono Direct Box at a Glance:
  • Full-range passive direct box
  • Custom isolation transformer eliminates noise
  • Really easy to use
  • Built like a tank

Passive vs. Active DI
The Radial ProDI and ProD2 (stereo version) are full-range passive direct boxes. Active direct boxes employ electronic circuits to change the impedance from hi-Z to lo-Z and balance the signal. Passive DIs instead employ a simple passive transformer to do the work. Active DIs require batteries, 48V phantom-power or external power supplies to power their circuits, while passive transformer-equipped direct boxes do not require any power to perform their task. The advantage of a transformer over typical active circuits can be summarized as "a great device to reduce system noise" in a sound system. To accomplish the task of noise elimination, the Radial ProDI and ProD2 features first-class transformers and require no batteries or power supply.

Custom Isolation Transformer
The Radial ProDI is equipped with a custom-made audio transformer, which provides exceptional signal handling without saturation. More importantly, the ProDI's custom transformer has extremely low phase distortion in the critical bass and mid regions. The ProDI's transformer provides 100% isolation, to eliminate hum- and noise-causing ground loops, while maintaining signal integrity. Inside the ProDI you'll also find isolated XLR connectors, to eliminate chassis ground potential, as well as a military-spec PC board, with a full surface ground plane to reduce susceptibility to RF noise. The result is exceptional clarity and definition, at an attractive price point.

Really Easy to Use
The best feature of the ProDI is "plug and play" ease of use. All you do is connect the instrument to the 1/4" inputs, the 1/4" through jack to the stage amplifier(s) or mixer and the XLR output to the mixing console and you are done. Any distortion? Hit the -15dB pad. Any noise? Just depress the ground lift switch. You will find that with acoustic guitars and basses, the natural tone of the instrument will shine through with a smooth and musical rendering. For electrically powered devices, such as keyboards, the ProDI will immediately eliminate troublesome ground loops while delivering solid dynamics, with a full rich sound.

Solid Construction
Look inside a ProDI and you'll find the build quality and components to be of only the highest professional standards. Radial's proven construction methods and materials ensure years of trouble-free service — able to withstand the rigors of the most demanding, high-use professional environments. Radial pioneered the use of its innovative "book cover" design, which provides a protective zone around the switches and connectors that keep the components safe. The 14-gauge welded I-beam inner chassis and 14-gauge outer shell found in the ProD2 and ProDI greatly reduce the possibility of torque stresses being applied to the PC board. Stress on circuit boards causes broken and intermittent solder joints, a common cause of failure in commercial rental and other high-use environments. A full bottom no-slip rubber pad works double-duty by providing protection from electrical shock and making sure these DI's stay put.

Radial ProDI Passive Mono Direct Box Features:
  • Full-range, passive direct box
  • Isolation transformer eliminates noise
  • Very low harmonic and phase distortion
  • Compact and rugged design
  • Ideal for live sound and studio.
  • Isolated XLR connector eliminates chassis ground potential
  • Custom audio transformer on input provides 100% isolation to eliminate hum- and noise-causing ground loops, while maintaining signal integrity.
  • Military-spec PC board, with full surface ground plane to reduce susceptibility to RF noise
  • High-grade switches — long life, high cycle for reliable performance
  • 14-gauge steel welded I-beam construction makes it virtually impossible to torque the PC board
  • -15dB pad reduces the level going in from loud sources that could overload the circuit and cause distortion
  • Book-end design creates a protective zone around the switches & connectors, indestructible 14-gauge steel construction
  • Full no-slip rubber bottom pad provides mechanical isolation, electrical insulation and prevents unit from sliding around
  • Balanced male XLR output connector, AES standard with pin-1 ground and pin-2 hot
  • Lift switch lifts the ground to pin-1 on both channels.
  • Heavy-duty baked enamel finish for excellent durability
The Radial ProDI offers superb performance, at an affordable price — ideally suited for use with acoustic guitar, bass, and keyboards!

Tech Specs

Type Passive DI
Channels 1
Inputs 1 x 1/4"
Outputs 1 x XLR, 1 x 1/4" thru
Height 1.75"
Width 2.75"
Depth 4.25"
Weight 1.2 lbs.
Manufacturer Part Number R800 1100

Customer Reviews

Based on 34 reviews
Write your review

Fixed our problem!!

Now that we are using these for our acoustic guitars, the sound is awesome and we have eliminated the squealing problem when we tried to push the volume.
Music background: Church musician

Tone Unveiled

Let's face it, a DI box is not the sexiest thing you can buy. They usually get buried under a pile of cables or stuffed in a rack. A they're pretty much all the same, right? Especially passive DIs...there's just not that much going on inside them. At least, that's been my thinking for years. I've had a couple of Whirlwind Commander DIs I've been using since the 80's. They've never failed me, and I though they sounded pretty good. And at the time I bought 'em, they were pretty much the darlings of passive DIs. Fast forward to 2014. I had been loaning a band mate one of those Commanders for sometime, and had need for it back. He told me to order him a replacement and swap 'em out. After having previous experience with Radial gear, knowing that it's built like a tank, and seeing them on pretty much every major tour out there I felt good about using the ProDI. When it came it, I was impressed with the fit, finish, and heft of the box. The ground life and attenuation switches felt solid, as did the 1/4" connections. This thing could probably survive getting run over by a fork lift (note: I take no responsibility if you decide to test that theory). We got it installed in the bass rack, and at the next gig line checked it through the PA. Holy smokes!!!! Where did that bottom octave come from? I swear, it was like disengaging a high pass filter somewhere in the signal chain...we had never heard low end coming off the bass like that before. And not a sloppy, loose low end. Smooth, tight, defined...just the way it should be. Just goes to show you how much the transformer in a passive DI affects the tone. This was just night and day. Do yourself a favor next time you need a passive DI...spend a few extra bucks and spring for the ProDI. It's the best tone for the buck out there!
Music background: Guitarist, Bassist, FOH Engineer

You definetely get what you pay for

I used to use a Behringer DI100 as in some other stores, its got a good reviews. But recently I had to buy another DI box for an active bass guitar, and then i realized how bad was the performance of the DI100. You can get cheaper DI's in the market. But I have learned that it is wise to spend a little bit more money and get better products like this one. It is a very simple DI box, with no fancy stuff like the Radial JDI. But it will definitely do its job with an amazing quality, without having to break the bank. It is very easy to use, and your musicians will love it. You will not get disappointed.
Music background: Religious Live sound Engineer


Thanks to the wonderful delivery guy who left the package in front of my garage door, it got ran over...and it held up and still worked perfect. How's that for durability? Oh yeah, it sounds awesome!!!
Music background: live sound engineer

Awesome DI

I've used direct boxes before, both in live and studio applications. Usually it's been bass or acoustic guitar. I recently had the need to put a DI on my pedal board since my newest electric guitar has a piezo bridge in it. All I can say is I don't need to take an acoustic guitar with me to gigs any more. The ProDI is built like a TANK, too! The housing is 14 gauge press-broken steel. Run over it with your car, I dare you. You can't hurt it! Easily the VERY BEST DI under $100. Possibly the best DI under $200
Music background: Recording and Live Sound Engineer, Pro Musician

Sweetwater Advice

Simon Picazo

This is the best DI under $100, period. You will be amazed by the clean, powerful, noise-free signal it produces and kick yourself for not getting one sooner. Don't invest thousands in instruments and recording equipment and then skimp on a vital link in your chain. Houses of worship in particular have gobbled these up because at this price they can afford to outfit the whole worship band!
See also: Direct Input Boxes, Radial, Radial Direct Boxes