PRESONUS VXP - User manual

User’s Manual

VXP
MICROPHONE PRE-AMPLIFIER
SMART COMPRESSOR
DE–ESSER
EXPANDER
SEMI–PARAMETRIC EQUALIZER
USER’SMANUAL
Version1.0
1999, PreSonus Audio Electronics, Incorporated.
All rights reserved.

WARRANTY
PreSonus Limited Warranty
PreSonus Audio Electronics Inc. warrants this product to be free of defects in material and
workmanship for a period of one year from the date of original retail purchase. This warranty
is enforceable only by the original retail purchaser. To be protected by this warranty, the
purchaser must complete and return the enclosed warranty card within 14 days of purchase.
During the warranty period PreSonus shall, at its sole and absolute option, either repair or
replace, free of charge, any product that proves to be defective on inspection by PreSonus or
its authorized service representative. To obtain warranty service, the purchaser must first
call or write PreSonus at the address and telephone number printed below to obtain a Return
Authorization Number and instructions of where to return the unit for service. All inquiries
must be accompanied by a description of the problem. All authorized returns must be sent to
the PreSonus repair facility postage prepaid, insured and properly packaged. PreSonus
reserves the right to update any unit returned for repair. PreSonus reserves the right to change
or improve the design of the product at any time without prior notice. This warranty does not
cover claims for damage due to abuse, neglect, alteration or attempted repair by unauthorized
personnel, and is limited to failures arising during normal use that are due to defects in material
or workmanship in the product. Any implied warranties, including implied warranties of
merchantability and fitness for a particular purpose, are limited in duration to the length of this
limited warranty. Some states do not allow limitations on how long an implied warranty lasts,
so the above limitation may not apply to you. In no event will PreSonus be liable for
incidental, consequential or other damages resulting from the breach of any express or implied
warranty, including, among other things, damage to property, damage based on inconvenience
or on loss of use of the product, and, to the extent permitted by law, damages for personal
injury. Some states do not allow the exclusion of limitation of incidental or consequential
damages, so the above limitation or exclusion may not apply to you. This warranty gives you
specific legal rights, and you may also have other rights, which vary form state to state. This
warranty only applies to products sold and used in the United States of America. For
warranty information in all other countries please refer to your local distributor.
PreSonus Audio Electronics, Inc.
7257 Florida Blvd.
Baton Rouge, LA 70806
[phone]
[phone]
www.presonus.com

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1999, PreSonus Audio Electronics, Incorporated. All rights reserved.

TABLE OF CONTENTS
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1Overview
1.1 Introduction 4
1.2 Features 5
2 Controls&Connections
2.1 Front Panel Basic Layout 10
2.2 Mic Preamp Section 14
2.3 Smart Compressor 15
2.4 Expander 16
2.5 De – Esser 17
2.6 Equalizer 17
2.7 Master Section 19
2.8 Back Panel Wire Diagrams 20
2.9 Power Supply 20
3Operation
3.1 Dynamic Microphones 22
3.2 Phantom Powered Microphones 22
3.3 Insertion Points 22
3.4 Using Return as Line-In 22
3.5 96k/24-Bit Digital Output Card 22
4Technical
4.1 Specifications 24

1OVERVIEW
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1.1 INTRODUCTION
Thank you for purchasing the PreSonus VXP Voice Processor with
Microphone Preamplifier – De-Esser – Expander – 4 Band Semi-
Parametric Equalizer. The VXP by PreSonus is the only voice processor
on the market that features a transformer coupled, Class A Mic Pre, Preset
Compressor, De-esser, Expander, 4 band semi-parametric EQ, Peak
Limiter and an optional 96k/24 Bit digital output card. PreSonus Audio
Electronics has designed the VXP utilizing high-grade components to insure
optimum performance for an infinite period of time. We believe the VXP to
be an exceptional sounding unit and an exceptional value. We encourage
you to contact us at 1-800-750-0323 with any questions or comments you
may have regarding your PreSonus equipment. We value your suggestions,
highly. PreSonus Audio Electronics is committed to constant product
improvement. We believe the best way to achieve our goal of constant
product improvement is by listening to the real Experts on our gear, our
valued customers. We appreciate the support you have shown us through
the purchase of this product.
Please pay close attention to how you connect your VXP to your system.
Improper grounding is the most common cause of noise problems found in
studio or “live” sound environments. We would like to suggest that you use
this manual to familiarize yourself with the features, applications and correct
connection procedure for your VXP before trying to hook it up to your
system. Thank you, once again, for buying our product and may we wish
you Good Luck and enjoy your VXP!

OVERVIEW
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1.2 FEATURES
The following information is a summary of your VXP’s features:
vMicrophone Pre-Amplifier. Your VXP contains a Class A
discrete input buffer followed by a dual servo gain stage. This
arrangement results in ultra low noise and wide gain control allowing
the VXP user to boost desirable signal without increasing unwanted
background noise (NO capacitors!).
Ø48 Volt Phantom Power. The VXP has 48V Phantom
power available. This assures optimum performance of your
condenser microphones that require Phantom power and that
the power supplied will be free of noise or distortion.
ØPad. A 20dB pad is available for reducing the in-coming signal
level. This pad provides a more manageable signal from high
output devices giving greater control over the in-coming signal
and a much reduced chance of over-driving the input and
avoiding distortion.
Ø+24dBu Headroom. The VXP mic-pre has +24 dBu of
headroom. This feature gives you a very wide dynamic range
and excellent transient response characteristics.

OVERVIEW
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ØIDSS Control. The VXP offers a very high quality transformer
and features an IDSS control (this control adjusts the drain
current on the input FET amplifier altering the even harmonic
levels of the signal being passed) with an adjustment range of
0% to 100%. The 0% position passes a pure signal. As the
control is rotated to the 100% position, the signal’s even
harmonic series is boosted giving the signal “warmth” very much
like a vacuum tube or similar to the sound of analog tape
saturation. This remarkable effect gives you the sound of a tube
without the headache of uneven performance often encountered
with vacuum tube devices (“no tube to pick-up RF or to age
and become “microphonic”).
ØLED Meter. LED metering provides an accurate reading of
the input level and a fast reference of presence of signal.
vSmart Compressor with Pre-Sets. The VXP is equipped with a
Smart Compressor with 16 Pre-Sets designed especially for
processing voice.
Ø16 Pre-Set Compression Curves. The Compressor section
of the VXP has 16 pre-sets with varying degrees of
compression ranging from multiple settings graded and labeled
“Light”, ”Medium” and “Heavy”. These easy-to-use preset
parameters were derived from pro audio engineers with years
of recording experience to provide VXP owners with a wide
variety of “studio tested and proven” compression settings
uniquely suited for virtually any singing style or vocal
application.
ØIn / Out. The In/Out switch lets you compare the compressed
sound quickly to the uncompressed sound.
vExpander. The VXP’s Expander section utilizes a concentric

OVERVIEW
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control with the outer ring for threshold set and the inner knob for
ratio adjustments. This feature gives you the benefit of seamless
noise reduction through downward expansion ridding the signal of
unwanted background noise. A 4 segment LED meter monitors
the degree of expansion.
vDe - Esser. A variable De-Esser with a range of 800Hz to
8kHz removes unwanted sibilance (hiss or “S” sounds) while
allowing the signal to remain completely natural. The Threshold
control makes setting the De-Esser extremely precise and fine-
tuning a simple process. Above the controller, a 4 segment LED
shows the operation of the De-Esser and how much gain is
reduced to eliminate the sibilance.
v4 Band Semi-Parametric Equalizer. Total tonal control is what
the Equalizer section provides. Low and High Shelving coupled
with Low Mid and High Mid controls with an extremely wide
Frequency band and narrow “Q” will let you fine tune the sound
to suit your taste with exacting precision.
ØLow Shelving. The Low frequency control is fixed at 100
HZ with plus or minus 12 dB giving ample boost or cut at the
frequency.
ØQ Switch. A switchable Q function decreases or increases
the width of the frequency control parameters. The frequency
width is selectable from .5 or by a factor of 2.
ØLow Mid-Range. The Low Mid-Range control is a
concentric control with the outer ring for Level adjustments of
plus or minus 12 dB and the center knob for setting the
frequency(90Hz to 700Hz) of boost or cut.

OVERVIEW
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Ø80Hz. An 80Hz filter is provided for eliminating low frequency
noise. This lets you greatly reduce background noise such as
air conditioners or wind noise with the flick of a switch without
effecting the desired frequencies.
ØIn /Out Switch. An In /Out switch is provided to audition the
signal in an equalized version as compared to a direct
unaffected signal.
ØHigh Mid-Range. High Mid-Range is adjusted by way of a
concentric controller with the outer ring for Level changes of up
to plus or minus 12 dB and the center knob providing
frequency control from 450 Hz(0.45 kHz) up to 5.8 kHz.
ØQ Switch. The High Mid-Range Q allows a widening of the
frequency point by a factor of 0.5 to as narrow as 2 for
pinpoint adjustment of important mid band frequencies that are
the most prevalent frequency in the normal audible range.
ØHigh Shelving. A rotary control for boosting the high
frequencies by as much as 12 dB or cutting them by 12dB is
tuned to 12kHz for accurate recreation of the upper end of the
signal. The shelving contour accentuates the naturalness of the
sound for better adjustment of vocal signals.
vMaster Section
ØPeak Limit. The Peak Limit control adjusts the threshold
point that the output signal is not allowed to cross. This benefits
you by preventing overload of downstream devices such as
DAT’s and Hard Drives where signal overload is completely
unacceptable. This is done without “squashing” the signal in an
audibly apparent way like some peak limiters are prone to do.

OVERVIEW
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ØLevel. The output of the VXP is adjusted by the Level control
and is useful for compensating for gain loss due to compression
or to decrease output signal that boosting frequencies with the
Equalizer section may have caused. The output is variable from
–70 dB to +10 dB.
Power. A BIG RED lighted push-button power switch is located
on the front of the VXP for your convenience.

2 CONTROLS & CONNECTIONS
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2.1 FRONT PANEL BASIC LAYOUT
Notice that the front panel of the VXP is divided into six sections - section
one is the Mic Preamp.
The Mic Preamp section contains:
•Gain Control
•IDSS Control
•+48 Volt Switch
•-20db Pad
•LED Input Meter

CONTROLS & CONNECTIONS
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Compressor Section contains:
•Pre-Set Selector
•Level Control
•Process In/Out Switch
•Gain Reduction Meter

CONTROLS & CONNECTIONS
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Expander Section:
•Threshold Control (Outer Ring)
•Ratio Control(Inner Knob)
•LED Expansion Meter
De-Esser Section:
•Threshold (Outer Ring)

CONTROLS & CONNECTIONS
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•Frequency (Inner Knob)
•Gain Reduction Meter

CONTROLS & CONNECTIONS
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EQ section:
•4 Band Semi-Parametric
•Low Shelving Control
•Low Mid Q Select Switch
•Low Mid Level (Outer Ring)
•Low Mid Frequency Select (Inner Knob)
•80 Hz Filter Switch
•EQ In/Out Switch
•High Mid-Range Level Control(Outer Ring)
•High Mid-Range Frequency Control (Inner Knob)
•High Mid Q Switch
•High Shelving Control

CONTROLS & CONNECTIONS
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Master Section Includes:
•Peak Limiter Control
•Level Control
•Limiter LED Meter
2.2 MIC PREAMP SECTION
GAIN: This control provides 60dB of gain.
IDSS CONTROL: Selects the amount of increase (0% to 100%) applied
to the even harmonic series of the signal being amplified by the VXP. The
effect of manipulating the harmonic distortion is of increasing or decreasing
the apparent “warmth” of the signal. This feature is derived from
manipulating the drain current of the FET input buffer of the Mic Preamp.
Experiment with the IDSS control and see what type of sounds you can get
from your present microphone selection.
+48V: The 48 volts supplied by way of the XLR connector, provides
power for condenser mics and any other devices requiring continuous

CONTROLS & CONNECTIONS
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Phantom power through the XLR input. This power is supplied at a
constant level to prevent any degradation of audio quality.
PIN 1 GND
PIN 2 +48v
PIN 3 +48v
XLR connector wiring for Phantom Power
PAD: Engaging the Pad switch provides -20 decibels of attenuation with
the push of a button. This is a very useful feature for rapidly reducing the
level coming into the VXP and thus preventing the input signal from over-
driving (distorting) the input. This may occur due to high output level from a
microphone or other device. Padding the input serves to provide increased
“headroom” for the operator while lessening the likelihood of an input signal
overload.
2.3 COMPRESSOR
CONTROL: The knob labeled Control selects one of the 16 factory
preset compression curves. The amount of compression available ranges
from Light, Medium, to Heavy. The appropriate setting depends upon your
taste and application.
PRESETS
LIGHT: The five presets contained in the section labeled “Light” have
ratios ranging from 1.1:1 to 1.5:1. These settings are subtle and retain
most of the dynamic range of the input signal with only slight restriction of
the transient characteristics of the signal. These settings are appropriate for
vocals as normally encountered in Ballads that have quiet passages in the

CONTROLS & CONNECTIONS
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verse section with much louder portions of signal typically found in the
chorus sections of a song. The lower ratio settings give greater range within
the performance. These settings are useful for dramatic readings and any
type of spoken word performance.
MEDIUM: Five factory presets with Ratios ranging from 1.6:1 up to 2:1
are found in these settings. Using these presets would be effective when
more control over transients is necessary. Examples for applications where
this might be desired would be program content that is less uniform in
loudness and less variance is needed between the quieter and louder
portions of the signal being processed. A medium tempo song with a
vocalist who generally stays “on” the mic is an example where one of these
settings would be useful. Another vocal application might be a newscaster
or “on-air” talent reading copy for radio or television.
HEAVY: The group of six presets found in this section range from 2.5:1 up
to 8:1. These settings provide the greatest control over signal transient
content. The range within the performance is restricted with these settings
allowing the least divergence from the loudest to the quietest portions on the
signal being processed. These settings are very useful when control is more
important than the dynamics within a performance. A really rockin’ vocal
with the singer “eating the mic” is a type of application where the higher
settings really shine. If you are concerned with losing signal level during a
take or performance, these higher settings can assist you by keeping the
signal more consistent and reduce the need of constantly pushing the fader
up or down just to keep a uniform volume being sent out or recorded. The
engineers at PreSonus have done a remarkable job in designing a function
that is this effective at constraining the signal level, while at the same time,
manages to let the signal remain audibly transparent and sounding relatively
unaffected.
2.4 EXPANDER

CONTROLS & CONNECTIONS
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An Expander is a processing device used to increase the dynamic range of
the signal being processed through it or in the case of down ward
expansion, as in the VXP, to decrease the signal. Expanders can make
quiet sounds quieter and loud sounds louder. Downward expansion
provides a hybrid result, i.e., signals above the Threshold are untouched
while those below the Threshold are attenuated at a ratio set by the Ratio
control. In this application, downward expansion is used for noise
reduction. Setting the Threshold level to just below quietest vocal level and
adjusting the Ratio to 3:1 will cause the Expander to decrease the signal
below the point set by the threshold as soon as the vocal signal stops. This
level decrease will occur at the rate set by the ratio setting, in this case 3:1,
effectively eliminating any unwanted noise from coming through. The
resulting decrease in signal would be down to –30dB if the VXP
Expander’s Threshold had been set to –10 dB. The VXP’s Expander is
designed to operate below the selected Threshold at the amount determined
by the ratio setting selected. If the quietest signal was –10 dB as in the
example, then the decrease that automatically occurs with the –10 dB
threshold setting would be-30 dB at a ratio of 3:1.
2.5 DE-ESSER
A de-esser is a special type of compressor designed to operate only at
predetermined frequencies to reduce the effect of vocal sibilant sounds such
as S’s at the beginning and ending of words, for example. The VXP De-
Esser has a variable threshold range from –40 dB to +20 dB. The
frequency of operation is determined by selecting the most effective
frequency with the Frequency Range controller. It has a range from 800Hz
to 8kHz. Annoying “S” sounds can be completely removed leaving the
desired signal intact with the proper adjustment of the frequency and
threshold controls. The 4 segment LED shows the gain reduction occurring
due to the De-Esser functioning.