PRESONUS EUREKA - SCHEMA User manual

EUREKA
MICROPHONE PREAMPLIFIER
COMPRESSOR
PARAMETRIC EQUALIZER
USER’S MANUAL
version 1.0
?2003, 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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?2003, PreSonus Audio Electronics, Incorporated. All rights reserved.

TABLE OF CONTENTS
3
1 Overview
1.1 Introduction 4
1.2 Features 4
2 Controls & Connections
2.1 Front Panel Basic Layout 7
2.2 Preamplifier 9
2.3 Compressor 10
2.4 Equalizer 12
2.5 Master 13
2.6 Back Panel 13
2.7 Power Supply 14
3 Operation
3.1 Microphones 15
3.2 Send and Return 15
3.3 192k/24-Bit Digital Output Card 16
3.4 Application Settings 17
4 Technical
3.5 Specifications 22

1OVERVIEW
4
1.1INTRODUCTION
Thank you for purchasing the PreSonus EUREKA. PreSonus Audio Electronics has
designed the EUREKA utilizing high-grade components to insure optimum
performance for an infinite period of time. We believe the EUREKA 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. PreSonus Audio Electronics is committed to constant product
improvement, and we value your suggestions highly. We believe the best way to
achieve our goal of constant product improvement is by listening to the real experts,
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 EUREKA 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 EUREKA 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 EUREKA!
1.2 FEATURES
The following information is a summary of your EUREKA’s features:
Microphone Pre-Amplifier.Your EUREKA 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 EUREKA user to boost desirable signal
without increasing unwanted background noise.
?48 Volt Phantom Power. The EUREKA 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.
?Pad. A 20dB pad is available for reducing the in-coming signal level. This
pad provides a more manageable signal from high output devices giving

OVERVIEW
5
greater control over the in-coming signal and a much reduced chance of
over-driving the input and avoiding distortion.
?+22dBu Headroom. The EUREKA mic-pre has +22 dBu of headroom.
This feature gives you wide dynamic range and excellent transient response
characteristics.
?Saturation Control. The EUREKA offers a very high quality transformer and
features an SATURATION 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”).
?Variable Microphone Input Impedance.This feature enables you to “tune”
your microphone –by matching the output impedance of your microphone
with your microphone preamplifier. This works especially well for ribbon
microphones. Changing the input impedance is also effective for dynamic
and condenser microphones and can be the perfect solution for a given
recording application.
?Phase Reverse. Use the phase reverse switch to combat phase
cancellation with other open microphones.
Full Featured Compressor with High Pass Filter. The EUREKA is
equipped with a Compressor with a high pass side chain filter designed
especially for frequency specific processing.
?Soft Knee Compression. Soft Knee Compression causes the
compression to set in gradually producing a more musical response
?Bypass. The Bypass switch lets you compare the compressed
sound quickly to the uncompressed sound.

OVERVIEW
6
3-Band Parametric Equalizer. Total tonal control is what the Equalizer
section provides. The EQ will let you fine tune the sound to suit your taste with
exacting precision.
?Bypass Switch. A bypass switch is provided to audition the signal in an
equalized version as compared to a direct unaffected signal.
?Variable Q. Adjusts the width of the frequency band between wide and
narrow during equalization.
?EQ?COMP. Switches the order of the signal chain putting EQ before the
Compressor.
Master Section
?Gain Reduction to Meter. Shows gain reduction on the meter implemented
by the compressor.
?Level. The output of the EUREKA 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–80 dB to +10 dB.
?VU Meter. The VU meter provides an accurate reading of the output level
and a reference of signal presence. It can also be switched to monitor gain
reduction when using the compressor.

2 CONTROLS & CONNECTIONS
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2.1 FRONT PANEL BASIC LAYOUT
Thefront panel of the EUREKA is divided into four sections–Preamplifier,
Compressor, Equalizer and Master.
Preamplifiersection:
?Gain Control
?Impedance Control
?Saturation Control
?+48 Volt Switch
?-20db Pad
?Phase Reverse Button
?80Hz Filter
?Line Input Select Button
?LED Input Meter

CONTROLS & CONNECTIONS
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Compressor Section:
?Level Control (Attack, Release, Ratio, Threshold, Gain)
?Soft Knee Switch
?Bypass Switch
?Hi-pass Sidechain Filter
Equalizer Section:
?3 Band Parametric
?80 Hz Filter Switch
?Bypass Switch
Master Section:
?Level Control
?Gain Reduction to Meter Button

CONTROLS & CONNECTIONS
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2.2 PREAMPLIFIER
GAIN: Provides +52dB of gain for the microphone input and +44dB of gain for the
instrument input.
IMPEDANCE SELECTOR: Selects the amount of resistance that is applied to the
microphone input. This selector allows you to match (or intentionally mismatch)the
input impedance of the Eureka with the impedance of your microphone. As the
Eureka’s impedance is lowered, different filtering effects can result delivering a
tailored sound for a particular application.
SATURATION CONTROL: Selects the amount of increase (0% to100%) applied to
the even harmonic series of the signal being amplified by the EUREKA. 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 SATURATION control
and see what type of sounds you can get from your present microphone selection.
LINE: Selects the line input on the back as the input in use.When using the Line
input, the microphone preamplifier stageis bypassed and thus the GAIN,
IMPEDANCE and SATURATE controls are inactive.
+48V: The 48 volts supplied by way of the XLR connector, provides power for
condenser mics and any other devices requiring continuous phantom power through
the XLR input. This power is supplied at a constant level to prevent any degradation

CONTROLS & CONNECTIONS
10
of audio quality.
XLR connector wiring forPhantom Power
Pin 1= GND Pin 2= +48V Pin3= +48V
PAD: Engaging the Pad switch provides -20dB of attenuation with the push of a
button. This is a very useful feature for rapidly reducing the level coming into the
EUREKA 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 input signal overload.
80Hz: The 80Hz button is a low-end roll-off filter. When pushed in, the 80Hz button
causes all frequencies below 80Hz to beattenuated (dropped) by 12dB. This filter can
be handy in live and studio applications. For example, the 80Hz filter can help to
reduce the “boominess” or “muddiness” of a vocaland improve the overall clarity.
Ø (Phase Reverse): Reverses the polarity of the signal. Use the phase reverse
when recording with more than one open microphone to combat phase cancellation
between microphones.
INSTRUMENT:¼” TS connector. When an instrument is plugged into the instrument
input, the microphone preamplifier is bypassed and the Eureka becomes an active
instrument preamplifier.
2.3COMPRESSOR

CONTROLS & CONNECTIONS
11
THRESHOLD:Sets the level at which compression begins. The below and
above LED’s over the Threshold knob indicate whether the input signal is
below or above the Threshold setting. When the signal is above the
Threshold setting, it becomes ‘eligible’ for compression. Basically, as you
turn the Threshold knob counter-clockwise, the input signal is compressed.
(If you have a ratio setting of greater than 1:1.)
RATIO:Sets the compression slope. This is defined as the output level
versus the input level. For example, if you have the Ratio set to 2:1, any
signal level above the Threshold setting will be compressed at a
compression ratio of 2:1. This simple means that that for every 1dB of level
increase into the compressor, the output will only increase ½ dB, thus
producing a compression Gain reduction of 0.5 db. As you increase the
Ratio, the compressor gradually becomes a limiter. A limiter is defined as a
processor that limits the level of signal to the setting of the Threshold. For
example, if you have the Threshold knob set at 0 dB, and the Ratio turned
fully clockwise, the Compressor acts as a Limiter at 0 dB. This means the
signal will be limited to an output of 0 dB regardless of the input signal.
ATTACK:Sets the speed at which the compressor ‘acts’ on the input signal.
A slow attack time (fully clockwise) allows the beginning envelope of a signal
(commonly referred to as the initial transient) to pass through the
compressor uncompressed, whereas a fast attack time (fully
counterclockwise) immediately subjects the signal to the Ratio and
Threshold settings of the compressor.
RELEASE:Sets the length of time the compressor takes to return the Gain
reduction back to zero (no gain reduction). Very short Release times can
produce a very choppy or ‘jittery’ sound, especially in low frequency
instruments such as bass guitar. Very long Release times can result in an
overly compressed signal, sometimes referred to as ‘squashing’ the sound.
All ranges of Release can be useful at different times however and you
should experiment to become familiar with the different sound possibilities.
(Refer to the applications section of this manual for some ideas.)
SOFT:selects Soft Knee and Hard Knee compression curves. When this
button is pushed in, Soft knee compression curves are used, otherwise hard
knee compression curves are used. With Hard knee compression, the gain
reduction applied to the signal occurs as soon as the signal exceeds the
level set by the threshold. With Soft knee compression, the onset of gain

CONTROLS & CONNECTIONS
12
reduction occurs gradually after the signal has exceeded the Threshold,
producing a more musical response (to some folks).
2.4EQUALIZER
The EQ is divided into three sections or bands (Low, Mid and High) Each band has
the following controls:
GAIN: Controls the amount of cut or boost of the corresponding frequency.Each gain
control offers +/-10dB of attenuation.
FREQUENCY: Selects the center frequency of equalization.If the gain is set to 0, this
control will have no effect.
Q (Bandwidth): Controls the width of the frequency being adjusted. Q is defined as
the ratio of the center frequency divided by bandwidth. If the gain is set to 0, this
control will have no effect.The Q on the Eureka ranges from 0.4 (wide) to 2.0
(narrow). In octaves the Q on the Eureka ranges from 3 octaves to 2/3 octaves.
BYPASS: When pushed in, the EQ is no longer equalizing the signal.

CONTROLS & CONNECTIONS
13
2.5MASTER
MASTER (LEVEL): This control adjusts the output level of the EUREKA. It functions
as a master fader for the entire processing strip. It is useful for adjusting the overall
output level up or down to match the optimum input level of a recorder, mixer, etc.
GR TO METER: When pushed the VU meter reads Gain Reduction of the
Compressor. When not pushed, the VU meter reads output level.
2.4 BACK PANEL BASICLAYOUT

CONTROLS & CONNECTIONS
14
Connectors
All Input and Output connectors are servo balanced. XLRor ¼” TRS with the following
wiring standard:
XLR/TRS
PIN 1 / Sleeve GND
PIN 2/ Tip High (+)
PIN 3/ Ring Low (-)
INSERT: Return and Send connectorsare provided for use in conjunction with
audio processdevices such as reverbs, delays, de-essers, etc.
NOTE: The LINE IN jack does not work unless the LINE button on the front of the unit
is pushed in.
2.7 POWER SUPPLY

CONTROLS & CONNECTIONS
15
The Power Jack on your EUREKA accepts a standard IEC cord like those found on
most computers and professional recorders.
The Power button on the Eureka is located next to the Power Jack.
Note: The input power voltage is set at the factory to correspond with the country in
which it was shipped..

3 OPERATION
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3.1 MICROPHONES
The Eureka works great with all types of microphones including dynamic, ribbon and
condenser microphones. Dynamic microphones and ribbon microphones are
generally lower output devices and require no external power source. Condenser
microphones are generally more sensitive than dynamic and ribbon microphones and
typically require external 48V phantom power.
Microphone Input Impedance
You can adjust the input impedance on the Eureka to match or “tune” a particular
microphone to achieve a desired sound. Most microphone preamplifiers have a fixed
microphone input impedance of 1000 to 2000 ohms. The Eureka has five different
impedance values to select from: 50, 150, 600, 1500 and 2500.
Refer to your microphone specifications to find the microphone output impedance and
experiment with matching the Eureka’s input impedance with the microphone’s output
impedance. As the impedance on the Eureka is lowered, a resistive load is put on
the microphone. This will not damage a microphone. However lowering or raising the
impedance can create subtle coloring and filtering effects and can be a perfect
solution for a particular application.
3.2SEND ANDRETURN
The EUREKA features ¼” TRS balanced Send and Return jacks. These connectors
allow the use of external processors such as reverbs, de-essers, limiters, EQ’s, etc.
Simply connect the send jack, balanced or unbalanced to the input of the external
processor. Then connect the EUREKA’s return jack to the output of the external

OPERATION
17
processor. The signal is now routed out of the EUREKA, into the external processor,
then back into the EUREKA. The final, processed signal will be available at the
EUREKA output connector. The Send and Return signal will be inserted after the
microphone preamplifier, before the compressor.
3.3 192K/24-BIT DIGITAL OUTPUT CARD (OPTIONAL)
A 192K/24-BIT Digital Output Card is available as an option for the
PreSonus EUREKA. It has AES/EBU and SPDIF output connectors, as well
as, an auxiliary ¼” TRS analog Line input connector. The card has a
selectable sample rate of 192kHz, 96kHz, 48kHz and 44.1kHz. The A/D
converters provide psycho-acoustic dithering for improved BIT resolution
when conversion from 24-BIT to 16-BIT sampling is necessary. The ¼” TRS
Line input will provide the benefit of allowing two EUREKA‘s to share one
Digital Output Card and in so doing, share both sides of the A/D converter.

OPERATION
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3.4APPLICATION SETTINGS
The following are application settings to get you started in using your Eureka. Feel
free to experiment by pushing any and all buttonsand turning knobs to their extreme
values -remember there are no rules when creating music. Let your imagination and
ear guide and direct the way you set your Eureka.
Note that the application settings do not include the main preamplifier controls:
GAIN, IMPEDANCE and SATURATE. Set these preamplifier controls with the
compressor and EQ in bypass for initial levels and tonal quality. Use the 80Hz hi-
pass filter to roll off low frequency rumble and muddiness.
Once you get a sound that you like, go back to the IMPEDANCE and SATURATE
controls to further tailor your sound.
1. Vocal
CompressorSettings
Thresh Ratio Gain Soft Bypass Attack Release SC-HP
-18 6+2In Out Mid Mid 10
EqualizerSettings
LOW MID HIGH
EQ>Comp QGain Freq QGain Freq QGain Freq
Out n/a 0n/a Mid +22.2k Wide +420k

OPERATION
19
2. Acoustic Guitar
Compressorsettings
Thresh Ratio Gain Soft Bypass Attack Release SC-HP
-20 3+2In Out Mid Fast 10
Equalizersettings
LOW MID HIGH
EQ>Comp QGain Freq QGain Freq QGain Freq
Out n/a 0n/a Nar -23k Wide +3 18.5k
Nar=NarrowQ
3. Electric Guitar
Compressorsettings
Thresh Ratio Gain Soft Bypass Attack ReleaseSC-HP
-18 51In Out Fast Mid 10
Equalizersettings
LOW MID HIGH
EQ>Comp QGain Freq QGain Freq QGain Freq