High Voltage Direct Box

Tapping Into a Better Direct Sound

By Ed Ivey for Onstage Magazine - All Rights Reserved 4/1/01

My first bass was an old Gibson EB-something. It had this chicken-headed “Vari-Tone” knob that yielded wildly different sounds, from a tinny, single-coil thwack to a sludgy, über-bass woof. It’s hardly surprising that, twenty years later, the Avalon U5 High Voltage Direct Box has me pining for that long-lost four-banger. One good tool can often kindle fond memories of another.

A basic direct box simply takes any high-impedance 1/4-inch instrument signal and converts it to low-impedance XLR output to send to a mixer. Over the last decade, dozens of companies have begun offering powered mono and stereo direct boxes, using tube, solid-state, and hybrid designs. Avalon Design has made top-quality audio gear since the mid-Eighties. Their products include Class A vacuum tube and solid state microphone preamps, tube stereo compressor/EQs, mastering equalizers, opto-compressors, and more. At $595, the U5 is one of their lower-priced items. Nevertheless, it reflects Avalon’s mania for sturdiness and function. It’s expensive as DI’s go, but the U5’s flexibility and features make the unit worth it for the right user. A live performer who uses several instruments with varying outputs will love the U5’s adjustable gain boost and six EQ presets; the studio picker will appreciate the solid-state unit’s quiet and dependable 100 percent discrete Class A circuitry.

There’s More To Life Than Ground Lifts

The U5 is two rack spaces tall, one-half rack space wide, and a foot deep. Avalon’s heavy-duty steel case, attractive brushed aluminum front panel, and hardy stainless-steel hardware insure durability.

The front panel features a boost knob graduated by click-stop détentes in 3 dB steps to a total boosted gain of 30 dB, and a tone knob with six détentes. A high-cut filter switch reduces everything above 8 kHz by 3 dB. A speaker-to-input switch activates the U5’s back-panel speaker signal input; a signal LED triggers at–2 dB for reference. An active-to-thru switch delivers the U5’s post-boost/EQ signal to external devices. There’s also a tone defeat switch.

The back panel has a speaker-in 1/4-inch input for converting amp speaker signal to direct; balanced microphone and line XLR outs, headphones out, ground lift, and modular AC input. Optional rack ears allow for single or double-unit installation—a must if the U5 is to be used live. Every switch emits a “pop” when engaged, but this is a characteristic of DC-coupled solid-state circuits and comes with the territory.

Avalon left out two things some users might miss: a power switch and a global mute function. This means that, when performing live, you must depend on a sound tech to mute your channel if you want to avoid noise.

Instrumentally Effective

The best thing about the U5 is that it has 30 quality dB of boost, mated with six different EQ shapes that can be switched in an instant. A multi-instrumentalist who might use three separate DI’s onstage for fiddle, acoustic guitar, and mandolin—because each instrument has varying output level and sonic characteristics—will love being able to dial up a gain setting, notch in an EQ preset, and be playing in seconds. Variable gain boost is consistent, smooth, and powerful. The U5’s six preset EQ shapes are well-crafted and extremely useful. (Three of the presets are gentle variations on a flat EQ, intended for a variety of acoustic, string, and keyboard instruments; one setting is radically-gutted at about 900 Hz for electric bass guitar; and the other two have a low-end roll-off at about 120 Hz for general electric string instruments.)

The U5 upgraded the sonic quality and EQ on every instrument I tried. My Jay Turser knock-off Beatle bass has an anemic output, but boosting the U5’s gain to about 20 dB and using tone preset 4—which emphasized the low-mids—made the Turser’s normally-nasal tone sound much fuller and rounder, with meaty lows. On the other hand, the piezoelectric output on my Zeta electric upright bass is insanely bottom-heavy. House engineers routinely ask me to roll off my low-end by half or more, often resulting in a loss of warmth. To offset this, I used the U5’s presets 2 and 5, and set a relatively low boost gain. Boom! There it ain’t! No more 100 Hz rolling rumble; I was able to return my amp’s graphic EQ to a less-severe curve, crank my onboard active knobs for more harmonic riches, and my Zeta sounded punchy, focused, and tight.

Out Of The Doghouse

Then there’s my old Czech plywood string bass with passive Fishman piezos; it invites feedback in an almost demonic way. I generally use a Fishman battery-powered outboard preamp to kick the output up, while hammering the mids down on my Peavey amp’s graphic to kill feedback. But when the band cranks up, I often end up grabbing my P-Bass to compete in volume. The U5 might give the old doghouse a fighting chance. Setting the boost up about 70 percent and using EQ preset 2 strengthened my signal significantly, while reining in problematic midrange frequencies. Trying a series of electric and electric-acoustic guitars, both steel and nylon, furthered confirmed the U5’s tonal diversity. In particular, it helped my Harmony arch-top with a low-output vintage DeArmond pickup get appreciably louder than usual before feedback.

Use the Knob, Luke

The Avalon U5 definitely has a place in any studio. It should especially appeal to home recordists who need a variable-gain DI box they can also take on gigs. Players who shift between piezo-equipped acoustic instruments in live performance will find boost and tone settings to compliment almost any axe. The speaker-input feature is also excellent; I sent a Fender Twin’s extension speaker-out to the U5 and discovered deep, creamy low-mids in a Gibson SG’s clean tone that didn’t have the same punch and clarity running in the active-to-thru mode.

The perfect live use for the U5 might be what I call “cheating the soundman”—basically, tailoring your DI signal’s gain and EQ to your own specs before delivering to front of house. A electric string player using a small mixer to manage several instruments can send the mono sum to the U5 and control the direct sound that goes to the house mixer, thus cutting down on extra DI’s and exercising more personal discretion over his or her sound. Engineers are much less likely to monkey with your sound if it arrives in quality shape, and U5 certainly helps make that happen.

Oh, and that old Gibson bass? I smashed it doing a bad imitation of Pete Townsend at an unremarkable punk gig—impressing nobody—back when George, Sr. was president. I sheepishly gave the pieces to a guitar geek the next day, but sometimes I sure do wish I had that “Vari-Tone” switch back.

BIO Ed Ivey recently traveled to southern Mexico in search of the genuine banda sinaolense sound. Send e-mail to por mas informacion sobre este sonido suave!

U5 Specifications

Circuit Topology 100% discrete, high-voltage Class A
Gain Switched 3dB steps, maximum gain +30dB
Input Impedance 3,000,000 ohm unbalanced (single ended)
Maximum Input Level +24dBu unbalanced, 400w speaker input
Output Connectors (2) XLR type, pin 2 hot electronic balanced
Maximum Output Level (Class A) +30dBu DC coupled, balanced 600 ohms (mic and line out)
Headphone Output 0.5w into 600 ohms
Noise 20kHz Unweighted -100dBu minimum gain position
Distortion THD, IMD 0.1% at +10dB
Frequency Response, -/+0.5dB 5Hz to 100kHz
Frequency Response, -3dB 1Hz to 500kHz (input band limited)
High Cut Filter -3dB at 8kHz minimum phase design
Tone Selector Six position rotary switch, all passive filters
AC Power Internal toroidal AC supply
Dimensions 8.5 x 3.5 x 12 in (216 x 88 x 305mm)
Weight 7 lbs (3.2kg)
Rack mount kit (1) RM-1 Single U5 19 inch rack mount kit (holds one half rack unit)
Rack mount kit (2) RM-2 Dual U5 19 inch

2 U5's with RM-2 rackmount kit


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