Radial PZ Deluxe and Firefly Review

AG 240 December 2012 Cover

by Doug Young

A direct box (DI) is one of those essential pieces of gear that don’t get as much respect as the more glamorous parts of a guitarist’s signal chain. At their most basic, DIs perform a simple task: converting a high-impedance unbalanced guitar signal to a low-impedance balanced signal suitable for connecting to a PA system. However, by adding a little more functionality, a DI box can become the heart of your system, processing and routing your signal to multiple inputs (such as an amp and PA) while maintaining a pristine overall sound. Canada’s Radial Engineering is known for its high-quality line of DIs, which range from simple passive transformer-based devices like the ProDI to full-featured preamps like the Tonebone PZ-Pre. We took a look at two new active Radial DIs that offer features of interest to acoustic guitarists, the PZ Deluxe and the Firefly Tube DI.

PZ Deluxe

The PZ Deluxe is essentially a single-channel version of the popular Radial Tonebone PZ-Pre, with a slightly simplified feature set. The unit packs an impressive amount of functionality into a small, easy-to-use package. Plug your guitar into the 1/4-inch mono input, and the PZ Deluxe produces a low-impedance balanced XLR output suitable for a mixing board, as well as outputs that can route your signal to an amp and a tuner. A recessed switch allows you to match the input impedance to various pickups—high impedance (10 megohms) for passive piezo pickups or low impedance (6.8 kilohms) for active or magnetic pickups. When the high-impedance mode is activated, the PZ Deluxe also increases the input sensitivity to accommodate the lower output of most passive piezo pickups.

Moving beyond the basic DI functionality, the PZ Deluxe offers a set of features for shaping and controlling your sound, including a three-band EQ with a sweepable midrange, volume control, a two-position low-cut filter, and individual phase switches for the XLR and amp outputs. The unit has two footswitches: a mute (useful for tuning or switching instruments) and a boost control. The boost switch can increase your signal by up to 13 dB, based on the setting of a recessed control, which is more than enough extra volume to lift your guitar above the band for a solo.

I found the EQ controls to be very effective, with the sweepable midrange control being especially powerful. Having separate 180-degree polarity switches for the PA and amp outputs not only helps fight feedback but also allows you to make sure the PA and your stage amplifier are in phase. The PZ Deluxe also has a low-cut filter with three positions: flat, slight cut, and larger cut. The medium position seems suited for rolling off low-end mud without greatly affecting the tone of a guitar, while the most extreme setting audibly reduces the amount of bass on a standard-tuned guitar.

I tried the PZ Deluxe with a variety of pickups, including an active D-Tar Wavelength undersaddle transducer, Taylor Expression System, passive L.R. Baggs M1 magnetic pickup, and passive K&K Mini soundboard transducers. In all cases, the sound was pristine, robust, and warm, and the EQ proved very effective at dialing in a good tone from each. The preamp remained remarkably quiet even with the boost switch engaged. Although the input impedance switch had little noticeable effect with most of these pickups, choosing the right setting proved critically important when using the passive K&K pickup—the sound was thin and brittle with the low impedance setting, but full and warm with the higher impedance.

SPECS: Preamp/DI. Class A FET preamp. Controls for gain and three-band EQ (with sweepable midrange). Low-cut and phase invert switches. Footswitches for mute and gain boost. Balanced XLR output. 1/4-inch unbalanced and tuner outputs. Switchable low (6.8 kilohms) and high (10 megohms) input impedance. 600-ohm output impedance. 20 Hz-18 kHz frequency response. 6.1 x 3.8 x 2.1 inches. 1.75 lb. 15-volt DC external power supply. Made in Canada.

PRICE: $250 list/$199 street.

MAKER: Radial Engineering: (604) 942-1001; radialeng.com

Firefly Tube DI

In addition to the basic function of a DI— converting a guitar’s high-impedance unbalanced output to a low-impedance balanced signal—many players feel that the transformers used in a DI’s circuitry also add warmth to their sound. The Radial Firefly is a transformer-based DI that goes one step further by adding a tube amplification stage. Like transformers, tubes are often credited with adding a sense of warmth to the sound, and the Firefly combines the benefits of both.

The brightly colored Firefly is a relatively large, heavy box with a hefty external power supply. The unit has a pair of unbalanced 1/4-inch inputs, which can be used to connect two instruments, although only one input can be used at a time. Each input has a trim control, and you can switch between inputs by pressing a switch on the front panel or with an optional footswitch (which can also be used to mute the signal), making the Firefly useful for those who need to switch between multiple instruments. An effects insert allows you to add effects devices that can be applied to both inputs.

On the output side, the Firefly has a balanced XLR for connecting to a PA or recording console, an unbalanced 1/4-inch auxiliary output that can drive a stage amplifier, and a tuner output. A master volume control affects both the XLR and 1/4-inch amplifier output, and both outputs can be muted with an optional external footswitch. The Firefly also has phase-reverse and ground-lift switches, and a pre/post switch controls whether the amplifier output comes before or after the tube circuitry. The only EQ control is a variable low-cut filter that, when fully engaged, rolls off frequencies below about 500 Hz, reaching -25 dB at 100 Hz.

One unusual feature of the Firefly is the "drag" section. By default, the Firefly’s input impedance is 4 megohms, suitable for passive piezo pickups as well as active pickups. However, with the drag switch activated, you can continuously vary the input impedance from 22 kilohms to 500 kilohms. This feature is useful for dialing in the best tone from passive magnetic pickups, which tend to react and sound differently depending on their input impedance.

Testing the Firefly with the same array of pickups I used with the PZ Deluxe, I again got a pleasing tone from each pickup. The Firefly produced a warm, beefy sound that would be especially useful when recording with a pickup and delivered a strong signal to both the XLR and amp outputs. The low-cut filter was useful for cleaning up the low end of the signal and could be used to tame a boomy guitar. The effect of the drag control was subtle with the pickups I tried, but it could potentially be an important feature for some.

SPECS:  Dual input (switchable) DI featuring a Class A FET front end, coupled with a 12AX7 tube drive circuit. Balanced XLR, unbalanced, and tuner outputs. Effects insert. Level control. Trim controls for each input. Mute switch with optional remote footswitch. 22-500 kilohms variable input impedance, switchable to 3.9 megohms fixed impedance. 150-ohm output impedance. 20 Hz-20 kHz frequency response. Rack-mountable with optional kit. 5.25 x 8.25 x 1.75 inches. 3.95 lb. 16-volt external power supply. Made in Canada.

PRICE: $700 list/$599 street.

MAKER: Radial Engineering: (604) 942-1001; radialeng.com

Tubes or Solid State?

The PZ Deluxe and Firefly both provide clear, pristine tone and handle the essential task of interfacing a guitar with a mixing board, as well as routing the signal to a tuner and stage amplifier. Both DIs feature exceptionally rugged construction that should hold up onstage, in the studio, or on the road, and provide worry-free performance. Beyond that, each unit offers somewhat complementary functionality that addresses different needs. The PZ Deluxe feature set should be familiar to guitarists used to working with preamps. With its flexible routing, support for passive and active pickups, and adjustable boost and mute switches, it would make a great central hub for any live rig, and the powerful EQ section allows you to create a wide range of tones.

The Firefly also offers useful features for the stage—especially the multiple switchable inputs—and should be especially welcome in the studio, where its transformer output and tube circuitry promises to warm up the sound of any pickup, while the continuously variable input impedance can help fine tune the sound of passive magnetic acoustic pickups.

Which DI is right for you will depend on whether you want the subtle warming effect of the Firefly’s transformer and tube or the flexible tone shaping of the PZ Deluxe’s EQ section.

Excerpted from Acoustic Guitar December 2012

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