Radial Engineering

PZ-DI - Piezo-Optimized Direct Box

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  • PZ-DI - Piezo-Optimized Direct Box
  • PZ-DI - Piezo-Optimized Direct Box, input/output jacks
  • PZ-DI - Piezo-Optimized Direct Box,  manual
Our Low Price: $279.99

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Radial Engineering has long been known for extremely durable, reliable, great-sounding direct boxes. It's kind of "their thing." They've recently come out with a new model, which specifically addresses the needs of upright bassists like us - and it's equally useful for your upright AND electric bass gigs!

The new Radial PZ-DI is a direct injection (DI) box that is specifically designed to accommodate the unique impedance needs of a piezo-based pickup (which is what most of us have on our basses, be it a Realist, Bass Max, Full Circle, etc.) The ultra-high 10 meg-ohm impedance is used to compensate for the harsh, quacky tone that some piezo pickups exhibit. But they didn't limit it to that - a useful input impedance switch allows you to choose two other settings as well. The 1 meg-ohm position delivers the classic impedance found on most active DI boxes. Amd the 220k-ohm setting warms up the tone of a magnetic pickup to give you the feel and tone as if connected to a tube amplifier. So it's very flexible; bring it to your upright bass jazz gig on Friday night, and your "slab" bass blues job on Saturday!

What is a DI box? It's your primary connection to the sound guy (or gal.) The means for getting your bass into the house sound system. Many amps have them built in - but oftentimes a sound person wants the uncolored sound of your bass fiddle, not a bass sound that's been "fiddled with" (with all the EQ knobs on your amp.) This box takes the feed directly off your pickup, before it hits your stage amp (and its settings) provides a high-impedance matched signal, and sends it to an XLR plug that goes straight to the mixer. There is also a 1/4" pass through jack so you can also send it to your stage amp.

Is it a preamp? Well, it's got the all-important impedance matching, but doesn't have the fancy EQ and other controls that a preamp might. But it does have some very useful tone-improving features, as well as a phase switch for feedback fighting.

For one, it has an adjustable high-pass (low cut) filter, which can allow you to dial out subsonic "flab" in your signal, tightening up your bottom end and reducing rumble. It also has a high-cut filter, which can often cut down on that "clacky-ness" that over-enhances the string sounds of plucking (and scratchiness of bowing.)

To maximize signal handling and reduce distortion, the PZ-DI incorporates an innovative DC to DC switching supply that converts the phantom power to deliver extra headroom. This provides ample dynamic range for acoustic instruments. Should an extra loud source such as an active bass or digital keyboard be encountered, simply activate the -15dB pad to rectify the situation. Other problem solvers include that (previously mentioned) 180 degree polarity reverse (phase) switch to tame hot spots on stage that can cause feedback, and a ground lift switch to help eliminate hum and buzz caused by ground loops.

The unit is only powerable by Phantom Power through the XLR cord, so it's use is specific to the sort of playing situation I mention above. It would be a VERY handy box to carry around in one's gig bag if one was a touring bassist; it could be a very good equalizing factor when you don't know what sort of bass or pickup you might end up with at tonight's gig. But as I mentioned, it's a very flexible bit of kit that can also be used on electric basses, guitars, mandolins, violins, keyboards... the list goes on.


  • Optimized for orchestral instruments on a live stage
  • Adjustable load for piezo and magnetic pickups
  • Variable low-cut filter to control bass resonance
  • 48V phantom powered, does not require batteries


  • Audio circuit type: Proprietary analog circuit with low-noise FET op-amp
  • Frequency response: 20Hz ~ 20kHz
  • Dynamic range: 105dB
  • Equivalent input noise: -98dBu
  • Maximum gain: +4.6dB
  • Total harmonic distortion: 0.02% /td>
  • Input impedance: 10M/1M/220K-Ohms
  • Input impedance with PAD on: 50K-Ohms
  • Output impedance: 200 Ohms - nominalt
  • Input pad: -15dB
  • XLR configuration: AES standard (pin-2 hot)
  • Power: 48V phantom - proprietary digital switching
  • Construction: 14 gauge steel chassis and outer shell, baked enamel finish
  • Size: 2.75" x 4.25" x 1.75" (70 x 108 x 45mm)
  • Weight: 1.2 lb (544 g)
  • FCC approval: Complies with section 15 of the FCC Rules
  • Warranty: Radial 3-year, transferable

Specifications are subject to change without notice.


WARNING: Cancer and/or Reproductive Harm
According to California state law, if you are a resident of California, we
must notify you that this product contains chemicals known to the state
of California to cause cancer, birth defects or other reproductive harm.
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Warranty Information

Standard Warranty:
All products sold by RADIAL come with a 1-year limited warranty. This limited warranty protects you against defects in workmanship. The warranty does not cover any consequential or inconsequential damage or any losses. Specifically, if you have a problem due to defect, you must make the arrangements and cover the costs to return the product to us with a copy of the original sales invoice and we will repair the product and return it to you at our cost. All warranty claims require a return authorization. Contact the RADIAL service department for details.

Transferable 3-Year Warranty:
Some RADIAL products come with a 3-Year Transferable Warranty. This means that if you buy the product and decide to sell it, the warranty can be transferred to the person that buys it, thus providing continuous warranty support and added value. This Transferable Warranty follows the same procedures and limitations outlined in the Standard Warranty. This means that if you sell the product, you must provide the buyer with a copy of your original invoice so that he, in turn, may be able to submit this should a warranty claim be required.

Warranty Limitation:
As with all typical warranties, only manufacturing defects are covered. Furthermore, parts that are subject to wear and tear such as switches, potentiometers and tubes are not covered under this warranty. This, however, does not mean that these will not be repaired or replaced free of charge. We pride ourselves in supporting the products we sell and will often exchange these parts free of charge pending the age of the device. This decision will be undertaken by RADIAL and in no way obliges the company to perform such tasks.
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