Presonus VXP User Manual
Product Reviews
Electronic Musician, June 2001
PreSonus VXP
By Myles Boisen
In the race to capture a share of your gear budget, many manufacturers have recently
rolled out flashy, high-powered, channel-strip-style processors oriented toward vocal
recording. The most stripped-down hybrid voice processors offer a single microphone
preamp, a compressor, and an equalizer; as you move up the scale, the units typically
provide better components and more features.
Among budget voice processors that cost less than $1,000, what you typically pay for
is a single, proven feature - for example, a good preamp or an acclaimed compressor
- with a mixed bag of mediocre extras thrown in. The single-channel PreSonus VXP
breaks the budget mold by offering a bountiful selection of high-quality, genuinely
useful processing stages, starting with a mic preamp that gives the top contenders a
run for their money.
STRING OF TOOLS
With its thick cool blue aluminum front panel and brushed aluminum knobs, the VXP
matches the look of the company's MP20 stereo mic preamp. The front panel is
divided into six segments according to function and has a big glowing "red eye" pushbutton power switch on the far right.
From left, first up is the mic preamp section, which provides a continuously variable
gain knob with 0 to 60 dB of gain marked in 10 dB steps. Next is the proprietary
IDSS control, which ranges from 0 to 100 percent. According to PreSonus, the IDSS
control allows for manual adjustment of the drain current on the input FET amplifier,
thus increasing even harmonic distortion as IDSS processing is added. That unusual
circuit modification is not intended to produce overload distortion associated with
guitar amps and fuzz boxes but rather to emulate the thickening effect of even-order
harmonic boosting in vacuum tubes.
Just above the gain and IDSS controls is a green eight-segment LED that indicates
preamp gain levels at -28, -14, -9, -3, 0, +3, +9, and +18 dB, with a red LED
assigned to the +18 dB value. There is no polarity-reverse switch, but 48V phantom
PreSonus Audio Electronics | 7257 Florida Blvd, Baton Rouge, LA 70806
T 225.216.7887 F 225.926.8347 | www.presonus.com
Product Reviews
power and a 20 dB attenuation pad are selectable from plastic push-button switches
that glow green when engaged.
The VXP's compressor portion traces its lineage to PreSonus' popular Blue Max
Smart Compressor. But unlike the Blue Max, which offers 15 presets and a manual
setting that allows for control over conventional parameters (ratio, attack time,
release time, and so on), the VXP's compressor provides only 16 presets: 5 Light, 5
Medium, and 6 Heavy. The presets are maximized for vocal applications, but
according to PreSonus, they are useful in other applications as well. The manual
doesn't disclose the individual presets' exact parameters, but it does give ratio ranges
for the three groupings - Light 1.1:1 to 1.5:1, Medium 1.6:1 to 2:1, and Heavy 2.5:1
to 8:1 - as well as general applications.
The compressor's input and output (make-up) gain controls are located on a
concentric, dual-pot control. By letting the signal level's adjustment be above or
below a preset threshold (determined by the compressor preset), the input-gain knob
functions essentially as a threshold control - a rather important point the manual fails
to mention. Input gain can vary from -12 dB to +18 dB; make-up gain is adjustable
from -20 dB to +20 dB. A backlit In/Out switch (bypass) allows for A/B comparison
of compressed and uncompressed signals. An eight-segment meter with green LEDs
indicates gain reduction at -1, -2, -3, -4, -6, -9, -12, and -18 dB.
A downward expander - designed for smooth, tapered fades of background noise - is
simple but surprisingly effective with just two controls on one concentric shaft. The
outer threshold ring adjusts the signal level at which the expander starts to work,
covering the entire dynamic range of most audio between its extremes of "off" (-70
dBu) and maximum of +20 dB. PreSonus thoughtfully gave the expander a ratio
control, which allows continuous manipulation of gated signals' gain reduction, from a
subtle 1:1 setting to the complete muting offered by an infinity:1 ratio. LED
metering is provided at four gain-reduction points: -3, -6, -12, and -24 dB.
A dual-function concentric knob also controls the de-esser. The inner shaft selects
frequency (continuously variable from 800 Hz to 8 kHz) and is targeted at prominent
or overly sibilant esses common in many vocal recordings. The de-esser's threshold
setting (-40 dB to +20 dB or "off") reduces gain only at the offending frequency and
typically passes bass and midrange frequencies untouched so that the de-essed signal
loses its sizzle but not its strength. A four-section meter - with green LEDs at -1, -3,
-6, and -12 dB - indicates the module's frequency-specific gain reduction. The deesser and expander sections do not provide a bypass, but they can be disabled by
setting their respective threshold controls to the clearly marked "off" positions
(counterclockwise for the expander, clockwise for the de-esser).
The VXP's 4-band equalization is implemented as separate high and low shelving
(fixed frequency at 100 Hz and 12 kHz respectively, -12 to +12 dB gain on both) and
PreSonus Audio Electronics | 7257 Florida Blvd, Baton Rouge, LA 70806
T 225.216.7887 F 225.926.8347 | www.presonus.com
Product Reviews
two concentric, semiparametric midrange controls. The low midrange knob covers
three octaves from 90 to 700 Hz, and the high midrange pot spans 450 Hz (marked
as .45 kHz) to 5.8 kHz. Bandwidth for each midrange EQ is selectable with a pushbutton switch, offering Q values of 2.0 or 0.5. A switchable 80 Hz low-cut filter is
included, and the EQ section can be bypassed through an In button.
The VXP's master section comprises a peak-limiter threshold control (brickwall type,
0 to +24 dBu or "off"), a master-level control (-70 to +10 dBu), and an output meter
identical to the eight-segment LED array in the mic preamp section. No meter
indicates gain reduction for the peak limiter.
GOOD CONNECTIONS
The VXP's rear-panel connections are simple: one balanced XLR microphone input,
separate _-inch balanced TRS send-and-receive insert jacks, and XLR and _-inch
output jacks for balanced or unbalanced operation, respectively. The insert return can
bring a line-level signal into the VXP for processing, and the send jack can also be
used when clean output (that is, without channel-strip processing) from the mic
preamp is desired. (The manual doesn't mention where the insert return point is in
the VXP circuit, but through testing I determined that it comes after the mic preamp
and before the compressor and subsequent options.) The line-input level also shows
up on the mic preamp input-level meter.
There is no provision for -10 dBV consumer-level output, though the master gain
control could easily be used to reduce gain to a level appropriate for -10 input
devices. A standard IEC power connector and AC voltage selector are on the rear
panel, as is a bay for the optional VXPD2496 digital-output converter and card
module ($399).
CARD-CARRYING MEMBER
I tested two VXPs: one with the digital card packaged separately and one with the
card already in place. The output card is a stereo converter, meaning that you need
to buy only one card to record digitally from a pair of VXPs. Just the same, I wanted
to try my hand at installing the VXPD2496 in the stock unit. The module was in place
in less than ten minutes, and the only difficulty I had was getting some screws out,
thanks to the VXP's solid construction.
VXP Specifications
Inputs (1) balanced XLR (mic); (2) balanced/unbalanced 1/4" TRS (send and
receive)
Outputs (1) balanced XLR; (1) balanced/unbalanced 1/4" TRS
Power Supply internal
Dimensions 1U 5 7" (D)
Weight 8 lbs.
PreSonus Audio Electronics | 7257 Florida Blvd, Baton Rouge, LA 70806
T 225.216.7887 F 225.926.8347 | www.presonus.com
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