Speck MicPre 5.0 Reference Manual

MicPre 5.0

Microphone Preamp & Mix Node

Reference Manual

Warranty

ii

Speck Electronics products are warranted to the original owner to be free of
defects in material or workmanship.

This warranty does not apply to any product subject to accident, misuse, neglect
or failure to comply with normal maintenance procedures or if the serial number
has been defaced, altered, or removed; nor will Speck Electronics accept
responsibility for damages resulting from improper installation, alteration or
unauthorized parts or repairs. If the product is modified by the customer without
permission, the customer agrees to pay for parts and labor necessary to remove
the modification before repair. The cause of the defect is in the sole judgment of
Speck Electronics.

Should a defect develop within one year of purchase from Speck Electronics or
an authorized dealer, Speck Electronics will supply the part or parts necessary at
no charge. Labor is covered in this warranty for a period of one year. Outside
service, repairs or pickups are not covered under this warranty.

Any item returned for warranty repair should be sent, if possible, in the original
packing container, prepaid to Speck Electronics, 341 E. Alvarado Street,
Fallbrook, California, 92028. If in our opinion the packing container is
improper for return shipping, we reserve the right to supply a new container at a
minimal charge.

In the interest of improving Speck products; designs and specifications are
subject to change without notice. It should be mentioned that if a change is
necessary for any reason, we make every effort to document
that change and send an "update notice" to all customers at no charge.

Notice

Edition

Speck Electronics makes no warranty of any kind with regard to this material,
including, but not limited to, the implied warranties of merchantability and
fitness for a particular purpose. Speck Electronics shall not be liable for errors
contained herein or for incidental consequential damages in connection with the
furnishing, performance, or use of this material.

This document contains proprietary information which is protected by copyright.
All rights are reserved. No part of this document may be photocopied,
reproduced, or translated into another language without the prior written consent
of Speck Electronics.

The information contained in this document is subject to change without notice.

All trademarks are the property of their respective owners.

First Printing - September 2002

Speck Electronics
341 East Alvarado Street
Fallbrook, California 92028
USA
760-723-4281
www.speck.com

Contents

Chapter 1 Introduction

Chapter 2 Installation

General .................................................................................

Standard Accessories ............................................................

Optional Accessories ............................................................

Operator Safety Summary .......................................................

Power source ........................................................................

Grounding the product .........................................................

Removing the cover .............................................................

General .................................................................................

Unpacking and inspection ....................................................

Environmental considerations ..............................................

Electrical grounding safety ..................................................

Mechanical installation ........................................................

Physical placement of adjacent equipment ..........................

Cleaning ...............................................................................

Repacking for shipment .......................................................

Basic connections to the MicPre 5.0 ........................................

The Input / Output connectors .............................................

Insert jacks ...........................................................................

Mixoutput jacks ...................................................................

Wiring the MP 5.0 to unbalanced inputs...............................

Mix Link Connector .............................................................

Connecting the MP 5.0 to the ASC Equalizer .............................

Interfacing two MP 5.0's..............................................................

Interfacing more than two MP 5.0's.............................................

Interfacing two MP 5.0's for M-S operation................................

iii

1
2
2
2
2
2
3

5
5
5
5
6
6
7
7
8
8
8
8
9
9
10
11
12
13

Chapter 3 Operation

General..................................................................................

Default control settings .........................................................

Signal flow diagram..............................................................

Front Panel Controls ................................................................

Gain switch............................................................................

Trim control ..........................................................................

Mic/DI select switch .............................................................

D.I. input jack .......................................................................

20dB Pad...............................................................................

48V Phantom switch .............................................................

Phase switch..........................................................................

Output select switch..............................................................

High Pass Filter control ........................................................

Filter bypass switch...............................................................

VU Meter ..............................................................................

Power indicator .....................................................................

Mix Level control .................................................................

Mix Pan control.....................................................................

Mix Mute switch ...................................................................

15
15
15
16
16
16
16
16
16
17
17
17
17
18
18
18
19
19
19

iv

Chapter 4 Wiring and Other

Rear Panel .................................................................................

Microphone input ..................................................................

Preamp output ......................................................................

O.S.P. switch .........................................................................

Insert jacks ...........................................................................

Pre Out-B / Line In jacks .....................................................

Mix output jacks ...................................................................

Mix Link connector ..............................................................

Aux DC output .....................................................................

Power switch ........................................................................

AC power inlet......................................................................

Fuse .......................................................................................

Specifications..............................................................................

General .................................................................................

Start simple ..........................................................................

Audio Cable ................................................................................

Connectors ...........................................................................

AC Distribution and safety .........................................................

Proper AC grounding ...........................................................

Quality AC system ...............................................................

AC distribution .....................................................................

Clock noise and AC .............................................................

Safety earth connection ........................................................

Audio earth ...........................................................................

Proper audio grounding and shielding ........................................

EMI and RFI ...............................................................................

Sources of EMI ....................................................................

Reducing EMI ......................................................................

20
20
20
21
22
23
23
24
24
24
24
24
25

26
26
26
26
27
27
27
27
27
27
28
28
28
29
29

v

Chapter 1 Introduction Section 1

Introduction

MicPre 5.0 - Microphone Preamp and Mix Node

General

Thank you for purchasing our MicPre 5.0 microphone
preamplifier. The MicPre 5.0 has operational features that are easy
to understand and you should be up and running in no time. If you
are unfamiliar with audio equipment or audio signal flow, it is
recommended that you read this manual. If you have any
questions regarding the MicPre 5.0 or any Speck product, do not
hesitate to contact Speck Electronics. Our phone number is
[phone].

The MicPre 5.0 is a complete single channel microphone preamp
that offers features and flexibility for use in recording, live sound
or any application that requires a high quality microphone preamp.

„ In this manual the MicPre 5.0 will also be referred to

as the MP 5.0.

The signal path consists of a matched discrete transistor front-end,
premium IC's, and transformer output stage. With the push of a
button, the MP 5.0 can change from a "Transformer-Balanced"
output to a "Active-Balanced" output.

The MP 5.0 also includes a mix section that makes it perfect for
DAW's and remote recording. With an optional interface cable, the
mix section of the MP 5.0 can linked with additional MP 5.0’s to
form a fully integrated mix section.

The compact ½ rack format of the MP5.0 can easily be rack
mounted and combined with the Speck Model ASC equalizer to
create a highly functional outboard channel strip.

The MicPre 5.0 is available in 2 versions; The Model MP5.0-NA
designed to operate with 100 and 120 VAC power, and the Model
MP5.0-EU that is designed to operate with 220, 230 or 240 VAC
power.

Chapter 1 Introduction Section 2

Standard accessories

Optional accessories

The MP5.0 is supplied with the following list of accessories:

Operations Manual

Power cord (NA version only)

(4) rubber bumpers - used for table top mounting or

stacking multiple units.

(2) 6-32 x ½” machine screws - supplied to mount the
MP 5.0 to an optional rack shelf.

The following is a list of optional accessories that are available

from the factory or your Speck dealer:

Mix link interface cables - to interface additional
MP 5.0’s.

2 unit cable - P/N MP50-Link2
4 unit cable - P/N MP50-Link4
6 unit cable - P/N MP50-Link6
8 unit cable - P/N MP50-Link8

Operator Saftey

Summary

Power Source

Grounding the product

M-S interface cable - a 12” cable used to connect two
MP5.0’s for use in a M-S micing configuration.

P/N MP50-MS

D.C. interface cable - Used to supply power to the
Model ASC equalizer.

P/N ASC-DCI

1U rack tray - may be used to rack mount two
MP 5.0’s or one MP 5.0 and one Model ASC equalizer.

The MP 5.0 is intended to operate from an AC power source that

does not apply more than 120 Volts RMS (Model MP5.0-NA) or

240 Volts RMS (Model MP5.0-EU) between the supply

conductors. Always make certain that power cord matches the

operating voltage shown on the rear panel above the power switch.

To avoid electrical shock, plug the power cord into a properly

wired receptacle. The ground pin of the power cord is internally

connected to the chassis. For safety reasons, do not lift the

ground on the power plug by using a ground lift adapter.

The MicPre 5.0 should never be exposed to rain or moisture.

Chapter 1 Introduction Section 3

Do not remove the cover

To avoid personal injury, do not remove the top cover of the
MP 5.0 and never operate the MP 5.0 without the cover properly
installed.

The MP 5.0 with its internal power supply contains voltages that
can cause serious injury or death. Refer all repairs to a qualified
service technician, or directly to Speck Electronics.

Chapter 1 Introduction Section 4

~ This page left intentionally blank ~

Chapter 2 Installation Section 5

Installation

General

Unpacking and inspection

Environmental considerations

The following information should give you the basics on how to
install the MP 5.0. The proper installation of the MP 5.0 as part of
a larger system requires a clear understanding of audio wiring, AC
distribution, grounding, and shielding techniques.

When the MP 5.0 is being installed into a larger system it may be
necessary to retain the services of someone experienced in these
matters.

The MP 5.0 is delivered in a special, protective shipping container
and was carefully inspected both mechanically and electrically
before shipment. It should be physically free of mars and scratches
and in perfect electrical order upon receipt. To confirm this, the
product should be inspected for physical damage that may have
occurred in transit. Any damage should be reported to your
delivery company as soon as possible.

If installed in an equipment rack that also contains heat producing
equipment, adequate ventilation should be provided. This will
prolong component life and maximize operational stability.

Electrical grounding safety

To insure adequate airflow around the unit and to prevent
overheating, we recommend leaving a 1U blank panel above and
below the MP 5.0 and do not obstruct the air vents on the side.

While the internal circuitry of the MP 5.0 is fully shielded by the
steel chassis, installation should nevertheless be planned to avoid
locating it immediately adjacent to power amplifiers, power
supplies, or any source of low frequency electromagnetic
emissions.

Merely affixing the MP 5.0 into an equipment rack is no guarantee
that the product is making a reliable ground connection. The
mounting rails in the equipment rack should never be depended
upon for a ground connection. To protect operating personnel, the
National Electrical Manufacturers Association (NEMA)
recommends that rack cabinets be grounded.

Upon loss of a protective ground connection, all accessible
conductive parts, including knobs and controls that may appear to
be insulating, can render an electric shock.

Chapter 2 Installation Section 6

To avoid electrical shock, plug the MP 5.0 into a properly wired
receptacle. The ground pin of the power cord is internally
connected to the chassis. For safety reasons, do not lift the

ground on the power plug by using a ground lift adapter.

Mechanical installation

The location of the MP 5.0 should be such that the operator has a
clear, unobstructed view of the front panel from his/her normal
operating position. The unit should also be within easy reach of
the operators normal position in order to facilitate the use of the
front panel controls

The ½ rack form factor of the MP 5.0 allows a single unit to be
mounted on a table top with the (4) rubber bumpers supplied with
the unit, multiple units stacked, or two units mounted side-by-side
on a 1U rack shelf manufactured by Middle Atlantic Products
(Model UTR1).

When attaching the MP 5.0 to the rack shelf, it should be secured
with the (2) 6-32 x ½” machine screws supplied with the unit. Do
not use screws that are longer than ½” in length as they could
damage the internal circuit board. When the MP 5.0 or multiple
MP 5.0’s are mounted to the rack shelf, they may be installed into
any 19" wide equipment rack that uses standard E.I.A. universal
spacing.

Physical placement of

adjacent equipment

Any device that emits a high EMI (Electro Magnetic Interference)
or RFI (Radio Frequency Interference) energy field should be
treated with suspicion. EMI is considered any unwanted signal
which adversely affects the operation of the MP 5.0 or the audio
system. This subject is discussed in Chapter 4.

Electronic equipment such as power amplifiers, power supplies,
video monitors, computers, certain synths and samplers must be
located away from the MP 5.0 and its associated audio cables. It
may be necessary to alter the positions of certain equipment that
you feel would cause buzzes or hums in the audio system.

Chapter 2 Installation Section 7

Cleaning

Repacking for shipment

The front panel is a high quality painted surface and the panel
lettering is applied using a silkscreen printing technique.

To clean the front panel, wipe the surface gently using a soft lint­free cloth to avoid scratching the panel or markings. Paper towels
are not recommended. Commercially available window cleaner
solutions may be used; however, the solution should be applied to
the cloth and not the panel to avoid the seepage of liquid to the
inside of the enclosure.

If the MP 5.0 is to be shipped to Speck Electronics for service or
repair, attach a tag to the product identifying the owner and
indicating the service or repair to be accomplished. Include the
model number and serial number of the product. Place the product
in the original container if available. If the original container in
not available, a suitable one can be purchased from Speck
Electronics.

If the original container is not used, wrap the product in heavy
plastic before placing in an inner container. Use plenty of packing
material around all sides of the product and protect panel faces
with cardboard strips. Mark shipping container with "Delicate
Instrument" or "Fragile", and insure the shipment for the proper
amount.

Note: Speck Electronics cannot be responsible for equipment that
arrives damaged or uninsured.

Chapter 2 Installation Section 8

Basic connections

to the MicPre 5.0

Input / Output connectors

Insert jacks

PRE OUT-B

INSERT SEND

MIX RIGHT

3

speck

electronics

O.S.P.

NORMAL

DIRECT

MicPre 5.0

OUTPUT

S/N

INPUT

2

1

AUX DC OUT

MIX LINK

6

4

LINE IN

OR

INSERT RTN

MIX LEFT

5

The XL mic input and XL pre output are the primary connections
to the MP 5.0. The XL microphone input (1) is designed to receive
a signal from any low impedance balanced microphone. The
preamp output (2) is a line level output and is switchable from
"Transformer-Balanced" or "Active-Balanced" output.

The Insert Send (3) and Insert Return (4) jacks provides line
level interstage access to connect a limiter or equalizer. Any
device interfaced to these jacks will be processed after the main
preamp gain stage and before the high pass filter section. The
processed signal is available at the main XL output, the left and
right mix outputs and the left/right output terminals on the mix link
connector.

Mix output jacks

Wiring the MP 5.0

to unbalanced inputs

The active-balanced TRS insert jacks serve a secondary function
on the MP 5.0. The Insert Send may be used as an additional
balanced Pre Out-B (3) and the Insert Return may be used as an
auxiliary Line In (4).

The active-balanced TRS left and right Mix Outputs (5) provide a
low impedance source for connection to the input of any balanced
line input.

The output circuits of the MP 5.0 were designed for balanced lines
and should only be connected to balanced inputs. If that is not
possible and it is necessary to connect to an unbalanced input, care
must be taken not to connect the low (-) terminal to ground.
If the low (-) terminal of these outputs are connected to ground, the
result will be a high level of audio distortion.

Chapter 2 Installation Section 9

If wiring the XL Pre Out for unbalanced operation, the cable
should be wired according to the diagram shown below in
Figure 1.

Do not

connect pin 3

2

1

3

Shield

Shield

To MP 5.0 XL output

To MP 5.0 output jack

Mix Link Connector

To unbalanced input

Figure 1. Unbalanced wiring for XL output

If wiring the Insert Send (Pre Out-B) or Mix Outs for unbalanced
operation, the cable should be wired according to the diagram
shown below in Figure 2.

Do not connect

ring terminal

Shield

To unbalanced input

Figure 2. Unbalanced wiring for TRS outputs

The Mix Link connector (6) is a RJ45 modular jack that allows the
mix section of the MP 5.0 to be combined with additional
MP 5.0's. The terminals on the mix link connector include the
left/right mix outputs and the left/right summing inputs.

A selection of standard and custom interface cables used to link the
MP 5.0’s are available from Speck Electronics or may be
assembled using standard 8 pin RJ45 modular plugs and 4
conductor cable.

The Pin-outs for the mix link connector are shown below in
Figure 3.

PIN 1PIN 1
PIN 2PIN 2
PIN 3PIN 3
PIN 4PIN 4
PIN 5PIN 5
PIN 6PIN 6
PIN 6PIN 6
PIN 8PIN 8

Mix Out - LeftMix Out - Left
Mix Out - RightMix Out - Right
GroundGround

GroundGround
Sum In - RightSum In - Right
Sum In- LeftSum In- Left

Figure 3. Pin-outs for mix link connector

1

8

Chapter 2 Installation Section 10

Connecting the MP 5.0

to the Model ASC EQ

With only a few simple connections, the MP 5.0 can be combined with
the Speck Electronics "Model ASC" 4 band equalizer to form a single
channel strip.

The following illustration shows how to interface the ASC equalizer to
the insert send/return jacks of the MP5.0 and how to power the ASC
from the Aux DC power source of the MP 5.0.

If you use the optional ASC-DCI cable, do not use the ASC power
module for the installation.

Connect one end of the ASC-DCI interface cable (green mark - face up)
to the connection marked “Aux DC Out” on the MP5.0. Connect the
other end of the interface cable (green mark - face up) to the connection
marked “Aux DC I/O” on the ASC. The plugs and respective connectors
are keyed so they will fit in only one direction.

speck

electronics

Fallbrook, California

Do not connect

the ASC

power module

POWER

USE WITH PS-4
POWER MODULE

Model ASC - 4 Band Equalizer

S/N

OUTPUT TRANSFORMER OPTION

AUX DC I/O

USE WITH SPECK
PRODUCTS ONLY

OUTPUT

GND

LIFT

RISK OF ELECTRICAL SHOCK - DO NOT

BAL. ¼

BAL. XLR

UNBAL.¼

HIGH

PIN 2

TIP

LOW

PIN 3

RING

PIN 1

SLEEVE

GND

INPUT

TIP

SLEEVE

CAUTION

OPEN OR EXPOSE TO RAIN OR MOISTURE.

115V (.2A)

230V (.1A)

AUX DC OUT

MIX LINK

LINE IN

INSERT RTN

MIX LEFT

PRE OUT-B

OR

INSERT SEND

MIX RIGHT

speck
electronics

O.S.P.

NORMAL

DIRECT

OUTPUT

MicPre 5.0

S/N

INPUT

ASC-DCI cable

Chapter 2 Installation Section 11

Linking two MP 5.0's

With only a simple connection, the mix sections of two MP 5.0's can be
summed together and operate like a multichannel mixer.

To link two MP 5.0's, an optional MP50-LINK2 mix link cable is
required. This link cable has RJ-45 modular plugs on both ends. One end
has a "clear" colored plug and the other end has a "red" plug. The MP 5.0
that receives the "red" plug is the unit that will become the master.

The illustration below shows how to link two MP 5.0's.

RISK OF ELECTRICAL SHOCK - DO NOT

CAUTION

OPEN OR EXPOSE TO RAIN OR MOISTURE.

115V (.2A)

230V (.1A)

AUX DC OUT

MIX LINK

LINE IN

INSERT RTN

MIX LEFT

PRE OUT-B

OR

INSERT SEND

MIX RIGHT

speck

electronics

O.S.P.

NORMAL

DIRECT

MicPre 5.0

OUTPUT

S/N

INPUT

CAUTION

Clear Red

MP50-LINK2 cable

RISK OF ELECTRICAL SHOCK - DO NOT

OPEN OR EXPOSE TO RAIN OR MOISTURE.

AUX DC OUT

115V (.2A)

230V (.1A)

MIX LINK

LINE IN

INSERT RTN

MIX LEFT

PRE OUT-B

OR

INSERT SEND

MIX RIGHT

To line inputs on a mixer,

DAT, or A/D converters

speck

electronics

O.S.P.

NORMAL

DIRECT

MicPre 5.0

OUTPUT

S/N

INPUT

Chapter 2 Installation Section 12

Linking more

than two MP 5.0's

With only a simple connection, three or more MP 5.0’s can be summed
together and operate like a multichannel mixer.

To link the MP 5.0's, an optional mix link cable is required. This link
cable has as many as eight RJ-45 modular plugs wired in a "daisy chain"
configuration. All of the plugs are a "clear" color except for a "red"
colored plug at one end. The MP 5.0 that receives the "red" plug is the
unit that will become the master.

The illustration below shows how to link multiple MP 5.0's.

RISK OF ELECTRICAL SHOCK - DO NOT

CAUTION

OPEN OR EXPOSE TO RAIN OR MOISTURE.

115V (.2A)

230V (.1A)

AUX DC OUT

MIX LINK

LINE IN

INSERT RTN

MIX LEFT

PRE OUT-B

OR

INSERT SEND

MIX RIGHT

speck

electronics

O.S.P.

NORMAL

DIRECT

MicPre 5.0

OUTPUT

S/N

INPUT

CAUTION

ClearClear

MP50-LINK6 cable

RISK OF ELECTRICAL SHOCK - DO NOT

CAUTION

OPEN OR EXPOSE TO RAIN OR MOISTURE.

115V (.2A)

230V (.1A)

AUX DC OUT

MIX LINK

LINE IN

INSERT RTN

MIX LEFT

PRE OUT-B

OR

INSERT SEND

MIX RIGHT

speck

electronics

O.S.P.

NORMAL

DIRECT

MicPre 5.0

OUTPUT

S/N

INPUT

CAUTION

Clear Red

RISK OF ELECTRICAL SHOCK - DO NOT

OPEN OR EXPOSE TO RAIN OR MOISTURE.

AUX DC OUT

115V (.2A)

230V (.1A)

MIX LINK

RISK OF ELECTRICAL SHOCK - DO NOT

OPEN OR EXPOSE TO RAIN OR MOISTURE.

AUX DC OUT

115V (.2A)

230V (.1A)

MIX LINK

LINE IN

INSERT RTN

MIX LEFT

LINE IN

INSERT RTN

MIX LEFT

PRE OUT-B

OR

INSERT SEND

PRE OUT-B

OR

INSERT SEND

MIX RIGHT

MIX RIGHT

speck

electronics

O.S.P.

NORMAL

DIRECT

MicPre 5.0

OUTPUT

To additional MP 5.0's

speck

electronics

O.S.P.

NORMAL

DIRECT

MicPre 5.0

OUTPUT

S/N

INPUT

ClearClear

S/N

INPUT

To line inputs on a mixer,

DAT, or A/D converters

Chapter 2 Installation Section 13

Interfacing two MP 5.0's

for M-S operation

With only a simple connection, two MP 5.0’s can be linked together for
M-S (Mid-Side) micing.

To link MP 5.0's for M-S micing, an optional link cable is required. This
link cable has a RJ-45 modular plug on one end, and a TRS ¼" plug at
the other end. The MP 5.0 that receives the RJ-45 modular plug is this
unit that will become the master.

The illustration below shows how to link two MP 5.0's.

RISK OF ELECTRICAL SHOCK - DO NOT

CAUTION

OPEN OR EXPOSE TO RAIN OR MOISTURE.

115V (.2A)

230V (.1A)

AUX DC OUT

MIX LINK

LINE IN

INSERT RTN

MIX LEFT

PRE OUT-B

OR

INSERT SEND

MIX RIGHT

speck

electronics

O.S.P.

NORMAL

DIRECT

MicPre 5.0

OUTPUT

Side

RISK OF ELECTRICAL SHOCK - DO NOT

S/N

INPUT

CAUTION

OPEN OR EXPOSE TO RAIN OR MOISTURE.

115V (.2A)

230V (.1A)

AUX DC OUT

MIX LINK

LINE IN

INSERT RTN

MIX LEFT

PRE OUT-B

OR

INSERT SEND

MIX RIGHT

speck

electronics

O.S.P.

NORMAL

DIRECT

MicPre 5.0

OUTPUT

Mid

S/N

INPUT

MP50-MS cable

To line inputs on a mixer,

DAT, or A/D converters

Chapter 2 Installation Section 14

~ This page left intentionally blank ~

Chapter 3 Operation Section 15

Operation

General

Default Control Settings

In this section we hope to give you basic information on the
operation of the MicPre 5.0 and adequately describe its controls,
switches, and connectors.

The information in this section of the manual is intended to help
with the technical process when using your MP 5.0. Words alone
could not adequately describe how to adjust the controls for every
situation you might encounter with the MP 5.0. You should
experiment with settings and micing techniques to achieve the best
results for any particular situation. Your ears should be your best
gauge of how to adjust the settings on the MP 5.0 to make the
sound fit your requirements.

Before any attempt is made to operate the MP 5.0, it would be a
good idea to set all the controls to their neutral positions. This
gives you a reference point to work from when adjusting controls
and switches. The Gain, HP filter, and Mix level controls should
be set to their full counter-clockwise setting. The Trim and Mix
Pan controls should be set to their “0” center detented position. All
pushbutton switches should be set to the "Out" position.

When any future reference is made to the controls or switches of
the MP 5.0, is will be assumed that they have been set to their
neutral positions.

Signal flow diagram

Use this signal flow diagram shown below (Figure 4) as a
reference when reading the descriptions of the controls and
connectors that follow in this chapter.

Figure 4. MicPre 5.0 signal flow diagram

Chapter 3 Operation Section 16

Front Panel Controls

1. Gain switch

2. Trim control

3. Mic/DI select

4. D.I. input jack

5. 20dB Pad

This 11 position rotary switch adjusts the mic gain in 5dB steps
from +10dB to +60dB. When the Mic/DI switch is selected for
D.I., the gain range is from -10dB to +40dB in 5 dB steps.

The trim control provides -10dB to +10dB of continuous
adjustment with a center detent of 0dB. A total gain of 70 dB is
available when the Gain adjust is set to 60, the Trim is set to +10,
and the -20 Pad is disabled.

This switch will select the microphone Input on the rear panel or
the ¼” D.I. input jack on the front panel. A yellow LED indicates
the operation of the D.I. input jack.

This Direct Input (D.I.)

1 2

jack will accept a

35

balanced or unbalanced
input signal and is
selected when the
Mic/DI switch is
depressed. This input

35

Gain

Gain

40

40

30

30

25

25

20

20

15

15

10

10

45

45

50

50

55

55

60

60

Trim

Trim

0

0

_

_

+

+

10

10

10

10

may be used for
electric guitar, bass, or
keyboards.

D.I.

D.I.

MIC

D.I.

D.I.

-20

-20

4 3 5 6

48V

48V

When this switch is
depressed, the
microphone input signal is reduced by 20dB. The D.I. input is
unaffected by this switch.

Application: There may be occasions when the minimum gain
settings (10 on the gain switch and -10 on the trim) is just not low
enough. This can happen when the mic is producing a very high
output.

Chapter 3 Operation Section 17

6. 48V Phantom

Important information

regarding phantom power

The phantom switch supplies a DC voltage of +48 volts to pins 2
and 3 of the XL mic input connector for powered microphones that
do not use their own external power supply. A red LED indicates
the operation of the phantom power.

Before using the +48 Phantom power switch, always follow
these rules:

uAlways check the user guide that comes with your

microphone regarding the use of phantom power. There is a
potential to damage your microphone if instructions are not
followed. In fact, most ribbon microphones can be
permanently damaged with 48V phantom power.

uAlways connect your powered microphone to the XL input

before depressing the phantom power switch.

uAlways be mindful that any audio gear that connects to the

output of the mic preamp (mixer, etc.) should be muted
before enabling the phantom power switch. When the
phantom power switch is depressed, it not only applies +48
volts to the powered microphone, but also induces a small
voltage into the mic preamp. This small voltage has the
potential, when amplified, to cause a very loud "thump" that
can damage a power amp and speakers.

7. Phase switch

8. Output select switch

9. HP frequency control

This switch reverses the polarity of the mic
input or D.I. input signal by 180 degrees. A red
LED indicates the operation of the phase
switch.

This switch will select either a "transformer­balanced" output or "active-balanced" output
for the main XL pre output. The selection of
this switch does not affect the Pre Out-B or the
Mix Outputs.

High Pass Filter Section

This High Pass filter section includes a variable
frequency control and a bypass switch. The HP
filter is helpful at eliminating unwanted low
frequency noise or just contouring the audio
band to roll off low frequency information.

This control adjusts the frequency from 30Hz
(Full CCW) to 250Hz (Full CW) with a slope of
12dB/octave.

Phase

Phase

Output

XFMR

ACTIVE

ACTIVE

50

30

30

140

BYPASS

250

250

7

8

9

210

10

Chapter 3 Operation Section 18

10. Filter bypass switch

11. VU Meter

12. Power indicator

This switch is used to enable or disable the High Pass filter circuit.
In the “out” position, this switch completely bypasses all filter
circuitry. When this switch is depressed, the HP filter is enabled.
A yellow LED indicates the operation of the High Pass filter.

This 10-segment VU (volume units)
meter will indicate the relative output
level of the mic preamp signal and is
sensitive from -15dB to +12dB in 3dB

-12

-15

0

-3

-6

3

-9

6

9

12

increments. A meter reading of zero VU
reflects a preamp output level of +4dBu,
the industry professional standard.

speck

speck

electronics

electronics

This VU meter circuit was designed to
approximate the ballistics of a "Taut
Band" analog style VU meter.

This LED will illuminate green when the power is applied to the
MP 5.0.

11

12

The Mix Section

The mix section of the MicPre 5.0 provides a separate left and
right mix output with level, pan and mute. The source of the mix
level may be the mic input, the DI input, or any line level signal
that is connected to the line in jack on the rear panel. The mix
section feeds the left and right mix outputs on the rear panel as
well as the left/right terminals on the mix link connector. The
adjustment to the mix section does not affect the signal at the main
XL output or the Pre Out-B.

With only a simple interface cable, this mix section, or “Mix
Node” can be linked with any number of MP 5.0's to form a fully
integrated mix section. In many situations such as desktop or
location recording, this expandable feature of the MP 5.0 can
eliminate the need for a separate audio mixer.

Chapter 3 Operation Section 19

13. Mix level control

14. Mix pan control

15. Mix mute switch

This control adjusts the level being

14

sent to the mix outputs. The
operation of this control does not
affect the signal at the main XL
output connector.

Level0Level

C

C

Pan

Pan

R

R

L

L

The pan control allows the mix
signal to be panned anywhere in the

MUTE

stereo perspective.

Depressing this switch removes the

13

MUTE

8

15

mix signal from the left/right mix
output and the left/right terminals of
the mix link connector.

Muting the mix section will not affect the signal at the XL pre
output, the Pre Out-B, or any signal returning into the left/right
summing input terminals of the mix link connector. A green LED
indicates the operation of the mute switch.

Chapter 3 Operation Section 20

Rear Panel

16. Microphone input

17. Preamp output

This microphone input XL connector is used to connect a low
impedance microphone.
The mic input is selected
with the Mic/DI switch on
the front panel. Before
connecting your

speck

electronics

MicPre 5.0

S/N

microphone, it is
recommended to set the
Gain to the 10dB setting

O.S.P.

33

and the 48V phantom
power switch to the off

NORMAL

DIRECT

OUTPUT

INPUT

position. The mic input XL
connector is wired as

18

17

shown below in Figure 5.

HIGHHIGH
LOWLOW

GROUNDGROUND

Figure 5. Mic input wiring

PIN 2PIN 2
PIN 3PIN 3
PIN 1PIN 1

This is the main output of the preamp. This XL output may be
“Transformer-Balanced” or “Active-Balanced” depending on the
switch setting on the front panel. The pre out XL connector is
wired as shown below in Figure 6.

121 2

16

Wiring the MP 5.0

to unbalanced inputs

connect pin 3

To MP 5.0 XL output

HIGHHIGH

LOWLOW

GROUNDGROUND

PIN 2PIN 2
PIN 3PIN 3
PIN 1PIN 1

Figure 6. Pre output wiring

Do not use the XL preamp output with an unbalanced input. When
wiring unbalanced cables and connectors, care must be taken not
to connect the low terminal (pin 3) to ground.

Any unbalanced XL plug interfaced to this connector should be
wired according to the diagram shown below in Figure 7.

Do not

2

1

3

Shield

Figure 7. Unbalanced wiring for XL output

Shield

To unbalanced input

Chapter 3 Operation Section 21

18. O.S.P.

(Output Signal Path)

The Output Signal Path (O.S.P) switch gives you the choice of two
paths for the signals originating at the mic or D.I. inputs and
exiting at the XL preamp output.

When set to the “Normal” position, the mic or D.I. signal will pass
through the main preamp stage, the insert send and return jacks,
and high pass filter section before passing to the XL output
connector. The "Normal" signal path is shown with the bold line in
the flow chart below (Figure 8).

Figure 9. Output signal path (O.S.P.) "Normal" setting

When the O.S.P. switch is set to the “direct” position, the mic or
D.I. signal passes only through the main preamp stage before
passing to the pre output XL connector. The “Direct” switch setting
bypasses the insert send and return jacks and the filter section. The
"Direct" signal path is shown with the bold line in the flow chart
below (Figure 9).

Figure 9. Output signal path (O.S.P.) "Direct" setting

Chapter 3 Operation Section 22

19. Insert Send and
Insert Return jacks

Wiring the MP 5.0

to unbalanced inputs

The MP 5.0 provides balanced TRS insert send and return jacks for
line level interstage access after the mic preamp stage and before
the high pass filter section.

The insert jacks may be used to connect limiters or equalizers. The
Insert Send jacks are wired as shown below in Figure 10.

HIGHHIGH

LOWLOW

GROUNDGROUND

Figure 10. Wiring for insert send and return jacks

TIPTIP

RINGRING

SLEEVESLEEVE

Do not use the Insert Send (Pre Out-B) with an unbalanced input.
When wiring unbalanced cables and connectors, care must be
taken not to connect the low terminal (ring) to ground.

Any unbalanced ¼" plug interfaced to this jack should be wired
according to the diagram shown below in Figure 11.

Do not connect

ring terminal

Shield

To MP 5.0 output jack

20. Pre Out-B and
Line In jacks

To unbalanced input

Figure 11. Unbalanced wiring for TRS outputs

The insert send and insert return serve a
dual purpose on the MP 5.0. The insert
send may be used as Pre Out-B. This

19 & 20

LINE IN

PRE OUT-B

signal is identical to the main pre out
except it is "active-balanced" and is not
affected by the Xfmr/Active switch on

INSERT RTN

OR

INSERT SEND

the front panel.

The insert return may be used as a

MIX LEFT

MIX RIGHT

balanced Line In for routing a signal to
the mix section.

21

Split Signal Path

The MP 5.0 has the ability to split into two discrete signal paths;
A mic or D.I. to the main XL output, and a line in signal to the
left/right mix outputs. The O.S.P. switch must be set to the
"Direct" position to use a split signal path on the MP 5.0.

Chapter 3 Operation Section 23

The signal flow diagram below (Figure 12) shows two separate
signal paths with the "mic to pre out" shown in a dashed line and
the "line in to mix out" as a solid bold line.

"Line In to Mix Out" signal path
"Mic input to Pre Out" signal path

21. Mix output jacks

Wiring the MP 5.0

to unbalanced inputs

Figure 12. Flow diagram for split signal path

These "Active-Balanced" TRS jacks are the left and right outputs
for the mix section. The signal present at these jacks are adjusted
by the mix level and pan controls on the front panel.

The mix outputs are available for interface to the input of an
external console, HDR, DAW, etc. The mix out jacks are wired as
shown below in Figure 13.

HIGHHIGH

LOWLOW

GROUNDGROUND

Figure 13. Wiring for mix output jacks

TIPTIP

RINGRING

SLEEVESLEEVE

Do not use the mix out jacks with an unbalanced input. When
wiring unbalanced cables and connectors, care must be taken not
to connect the low terminal (ring) to ground.

Any unbalanced ¼" plug interfaced to this jack should be wired
according to the diagram shown below in Figure 14.

To MP 5.0 output jack

Do not connect

ring terminal

Shield

To unbalanced input

Figure 14. Unbalanced wiring for TRS outputs

Chapter 3 Operation Section 24

22. Mix link connector

23. Aux DC output connector

The mix link connector
allows the mix section of
the MP 5.0 to be
combined with any
number of MP 5.0's to

RISK OF ELECTRICAL SHOCK - DO NOT

CAUTION

OPEN OR EXPOSE TO RAIN OR MOISTURE.

115V (.2A)

230V (.1A)

AUX DC OUT

form a fully integrated
mix section. The mix
link connector can also
be used to connect two

MIX LINK

MP 5.0's for M-S (mid­side) micing.

26

25 24 22

Refer to page 8 for mix
link pin-outs and pages 9 through 12 for examples of MP 5.0
interfaces.

This connector is available to provide a source of dual regulated
DC voltage to the Speck ASC equalizer and future Speck products.
An optional DC interface cable (p/n ASC-DCI) and instructions for
connection are available from Speck.

13 2

GroundGround

+16 VDC+16 VDC

-16 VDC-16 VDC

PIN 1PIN 1
PIN 2PIN 2
PIN 3PIN 3

23

24. Power switch

25. AC power inlet

26. Fuse

Figure 15. Pin-outs for Aux DC out

This power switch applies AC (mains) power to the MP 5.0. An
LED on the front panel will illuminate when the power is “On”.

This AC (mains) power inlet accepts a standard IEC power cord.
Before connecting the power cord, make certain that power cord
matches the operating voltage shown on the rear panel above the
power switch.

The 120 volt model (Model MP5.0-NA) is designed to operate
from 100 or 120 volts, 50/60Hz. The 230 volt model (Model
MP5.0-EU) is designed to operate from 220, 230, or 240 volts,
50/60Hz.

The ground pin of the power cord is internally connected to the
chassis. For safety reasons, do not lift the ground on the power

plug by using a ground lift adapter.

The AC power inlet has integral fuse holder that uses a
5mm x 20mm slow blow type fuse. To avoid the risk of fire,
always replace the fuse with the correct value fuse as marked on
the rear panel; .2 amp for the 120V model, or .1 amp for the 230V
model.

Chapter 3 Operation Section 25

Specifications

Gain Range (Mic)

70 dB total

Gain Range (D.I.)

THD+n

(Gain +40, Output +12dBu)

Noise EIN (22Hz-22kHz)

(150 ohm load, 60dB gain)

Freqency Response

Mic input impedence

D.I. input impedence

Maximum input level

Max. output level (10k load)

+10 to +60dB in 5dB steps

-10/+10 variable trim

-20 to +40 dB in 5 dB steps

.002% nominal

-126 dBu

10Hz-200kHz (+0/-3dB)

4.6k ohms

50k ohms

+18dBu (without pad)
+30dBu (with 20dB pad in)

+28dBu at active outputs
+24dBu at transformer output

HP Filter

Phantom Power

Dimensions

Weight

Power Requirements

30Hz-250Hz (12dB/octave)

+48V regulated

HxWxD=1.75" x 8.5" x 8.00"
(44mm x 216mm x 203mm)

5 Lbs. (2.27kg)

100-120 VAC 50-60Hz
220-240 VAC 50-60Hz

Chapter 4 Wiring and Other 26

Wiring & Other

General

Start simple

The following information is not specific to the operation of the
MicPre 5.0, but rather general information regarding the “care and
feeding” of an audio system.

A general discussion about AC, AC grounding, audio grounding,
EMI, and quality wiring is discussed in this section. These
subjects are very often overlooked or misunderstood, and should
be given consideration when interfacing your equipment to any
audio product.

A “quality” installation is essential when wiring any audio system.
When the time comes to actually interconnect your equipment,
proceed slowly. Interfacing the many pieces of electronic
equipment to your MP 5.0 and audio system should be a logical,
methodical process.

Start by connecting only your headphones or monitor power amp
to the mixer, and then add one line signal to the mixer at a time;
carefully listening and monitoring your progress. If a problem
arises, such as a buzz, hum, intermittent signal, or nonexistent
signal, stop at that point and solve the problem before proceeding.

Audio Cable

Connectors

Due to the high performance of the MP 5.0, it is recommended that
you use only the highest quality audio cable. A high quality cable
by definition, is a cable that provides good mechanical strength,
high microphonic noise immunity, high frequency response, low
crosstalk and 100% shielding ability. All audio cable used with the
MP 5.0 should be a 3 conductor foil shield type (2 inner conductors
and a shield drain conductor). It is not recommended that the 2
conductor "off the shelf cables" be used.

All wire and cable interfaced to the MP 5.0 should be terminated
with high quality connectors. A 1/4" plug or XL connector should
make a positive connection to its respective mating jack and
provide adequate strain relief to its cable. All connectors should
also have a metal shell to provide 100% shield for exposed
conductors.

Feel free to check with Speck Electronics for recommendation
when selecting cable and connectors.

Chapter 4 Wiring and Other 27

AC Distribution

and Safety

Proper AC grounding

Quality AC system

AC distribution

When you are evaluating voltage and current requirements for your
audio system, it is important that your MP 5.0 and/or audio system
does not exceed the capacity of your AC service. You should make
certain that the earth (green) wire for the AC system makes a
reliable earth connection, and determine as best as possible that the
AC system is free of noise that could generate unwanted audible
sounds or cause problems in microprocessor based equipment.

When using a larger rack system it is recommended that a
dedicated and isolated AC service be provided. This service
should have its own AC wires, isolated receptacle, and breaker and
not be shared with other unrelated equipment.

Even with an isolated AC system, it may still be necessary to make
use of surge protectors, line filters, isolation transformers, or all of
the above. Power conditioners should be selected with care, since
they sometimes generate undesirable switching noises in audio
systems.

When connecting many pieces of electronic equipment to an AC
system it is important that the AC is properly distributed. It is
better to connect all plugs to a common AC source than to have AC
receptacles in different locations.

When installing a large audio system, it may be necessary to
consult a qualified electrician that is familiar with the specialized
style of electrical wiring required for recording studios.

Clock noise and AC

Safety earth connection

Clock noise is one of the greatest enemies of the audio racks AC
system. If a computer or any microprocessor based device (most
samplers and effects are) emits or somehow couples its clock
signal with the neutral or earth of its own power cable, it will
contaminate your AC system and carry the clock noise into other
equipment; almost always with undesirable results.

The AC earth connection exists to protect you, your equipment and
possibly your building from an electrical disaster. In a properly
wired system, if a 120 volt AC wire were to break within your
equipment's chassis, it should make contact with the Safety Earth
Wire that is connected to the chassis, and blow the fuse or trip the
circuit breaker until the problem has been corrected.

Chapter 4 Wiring and Other 28

Given the same circumstances, if the AC safety ground has been
defeated with a ground lift or the AC service is incorrectly wired,
the equipment's chassis and quite possibly everything attached in
that rack would be "live" with 120 volts.

Audio earth

Proper Grounding

and shielding

In an electronics context, an earth provides a path for unwanted
EMI noise to be carried away from your audio equipment. If you
disable your earth with a ground lift or do not have a reliable earth
connection, the unwanted noise (EMI or RFI), will find an
electrical path of least resistance. That will most likely be your
audio equipment and would result in unwanted buzzes or hums.

In order for any audio signal to get from “Point A” to “Point B”
requires a cable with a minimum of 2 conductors. One conductor
is the hot, or high, or whatever you are familiar with; the other
conductor is the ground or common. Additionally, all audio wires
must be protected from environmental occurrences such as EMI
(Electro Magnetic Interference) and RFI (Radio Frequency
Interference) with an outer shield. An outer shield protects the 2
inner conductors from outside interference, and prevents that cable
from inducing its signal onto adjacent audio cables.

One common misconception is that the shield of a cable should act
as the common. This may be acceptable for guitar cords or semi­professional applications, but not for professional applications. The
audio signals must be carried only by the 2 inner conductors and
the shield must act only to cover these 2 conductors without
transmitting the signal from one location to another. It is
recommended that the shield be attached to the common (ground)
at one connector's end, and the shield not be connected at the other
connector's end. It is recommended that all shields be connected at
the mixer end, and the shields not be connected at the other ends
(synths, effects, power amps, etc.).

If a patchbay is utilized in your mixing system, the rules for
shielding change. With a patchbay, normally all shields are
connected at the patchbay jacks, and not connected at the mixer or
external audio equipment.

Chapter 4 Wiring and Other 29

EMI and RFI

The occurrence of EMI (Electro Magnetic Interference) and RFI
(Radio Frequency Interference) in a contemporary studio system
should be of great concern and not overlooked when installing the
MP 5.0. EMI is defined as any unwanted signal which adversely
affects the operation of the MP 5.0 or your audio system.

Stated simply, the undesirable effects of EMI may be perceived as
a low frequency smooth sounding 60Hz hum; a low frequency
"edgy" sounding 120Hz buzz; or a higher frequency "whine"
caused by the timing circuits in microprocessor based devices.
Almost every electronic device generates some amount of EMI
emissions. These emissions can be transmitted as electromagnetic
radiation or simply conducted though audio cables and power
cords. In the same respect, most electronic devices are also very
susceptible to the EMI emissions generated by other electronic
devices.

Sources of EMI

Reducing EMI

There are natural and man made sources of EMI that you can't do
anything about. These sources include radio, TV, and radar
transmitters, as well as motors, lights, and computers. Even the
Sun and atmospheric conditions can be contributors to noise that
you experience in your audio system.

There are generally 3 elements that must be present for EMI to
exist. These include the source of the EMI (conducted or radiated),
the propagation medium by which EMI is transmitted (directly on
the cables or through the air), and the receptor that suffers the
adverse affects of EMI. If any of these 3 elements are eliminated
or reduced, the EMI interference will be eliminated or reduced.

The more electronic equipment operating within a studio or
equipment rack, the higher the EMI emissions. The more audio
cable and low level audio equipment that exists within the same
proximity, the greater possibility of unwanted noise. The result of
EMI in an audio system manifests itself as a buzz, hum, whine, or
all three.

The most common EMI occurrence in an audio system is radiated
emissions from microprocessors in computeres, samplers, and
magnetic field sources from transformers and power supplies.