Speck EQF 810 Reference Manual

EQF 810

Audio Equalizer

Reference Manual

speck electronics

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

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.

Speck Electronic
341 East Alvarado Street

Fallbrook, California 92028
USA
1+760-723-4281
www.speck.com

Contents

Chapter 1 Introduction

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

Standard accessories ....................................................

Operator safety summary ...................................................

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

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

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

iii

1
2
2
2
2
3

Chapter 2 Installation

Chapter 3 Operation

Chapter 4 Wiring
and Other

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

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

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

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

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

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

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

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

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

Basic Theory of Equalizers ...............................................

Low-pass filter.............................................................

High-pass filter ............................................................

Bandpass filter.............................................................

Default control setting........................................................

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

Output select ...............................................................

Variable filters.............................................................

L - Low band controls ..................................................

L/M - Low/Mid band controls........................................

M - Mid band controls..................................................

H - High band controls .................................................

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

Input connectors ..........................................................

Output Cconnectors .....................................................

A.C. power inlet ..........................................................

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

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

Main voltage selector switch .........................................

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

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 ......................................................................

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Chapter 1 Introduction Section 1

Introduction

General

Thank you for purchasing our EQF 810 Equalizer. The EQF 810 has
operational features that are easy to understand and you should be up
and running in no time. If you have any questions regarding the
EQF 810 or any Speck product, do not hesitate to contact Speck
Electronics.

Speck Electronics
341 E. Alvarado Street
Fallbrook, CA 92028
Phone [phone]
email [e-mail]

The EQF 810 is a four band parametric equalizer and two variable
filters housed in a 1/2 rack space chassis that covers the audio spectrum
from a low 20Hz all the way up to 25kHz. It is well suited in audio
applications for professional recording, sound contracting, touring, or
any application where equalization is required.

Connect the EQF 810 to virtually any line level source: balanced,
unbalanced, or mixer inserts. The EQF 810 has high headroom that will
handle balanced signals up to +28dBu.

The EQF 810 design uses I.C. operational amplifiers for the active
electronics. All equalizer bands use state variable filter topologies and
the variable filters use a 2nd order Butterworth design. The line inputs
are active-balanced and the outputs are switchable between active­balanced or Jensen Transformer-balanced.

The EQF 810 is available in 2 versions;

• The Model EQF 810-NA designed to operate with 100 and 120

VAC mains power.

• The Model EQF 810-EU that is designed to operate with 220, 230

or 240 VAC mains power.

Chapter 1 Introduction Section 2

Standard accessories

Operator Safety

Summary

Power source

The EQF 810 is supplied with the following list of accessories:

• Operations Manual

• Power cord (North American version only)

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

multiple units.

• (3) 6-32 x ½” machine screws - supplied to mount the EQF 810

to an optional rack shelf.

The EQF 810 is intended to operate from an AC power source that
does not apply more than 120 Volts RMS (Model EQF 810-NA) or
240 Volts RMS (Model EQF 810-EU) between the supply conductors.
Always make certain that the power cord matches the operating
voltage shown on the rear panel.

Do not remove

covers or panels

To avoid personal injury, do not remove the top cover of the EQF 810
and never operate without the cover panel properly installed. If it
becomes necessary to remove the cover panel for service or to change
the mains operating voltage, always disconnect the power cable
before proceeding.

The EQF 810, 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 3

Specifications

Input Level

Output Level:

(Active Balanced)
(Transformer Balanced)

Input Impedance 30K Ohms

Output Impedance

(Active Balanced)
(Transformer Balanced)

Output Distortion(THD+n)
22Hz to 22KHz @ +4dBu

(Active Balanced)
(Transformer Balanced)

Frequency Response

Test Conditions:

AP balanced +4dBu signal connected to input.
All Boost/Cut controls set to “0”
LP and HP filters enable switches set “out”
4 Band EQ enable switch set “in”
Shelf switches set “out”
AP analyzer connected at output

Normal

+4 dBu

Normal

+4 dBu
+4 dBu

Maximum

+28dbu

Maximum

+28dbu
+24dBu

60 Ohms
600 Ohms

.0016%
.0025%

Measured at active balanced output

Measured at transformer output

Residual Noise Measurement

Test Conditions:

AP balanced signal connected to input.
AP Generator set “Off”
All Boost/Cut controls set to “0”
LP filter, HP filters, and Equalizer enable switches set “in”
Shelf switches set “out”
Transformer - Active output switch set “out”

AP analyzer connected at output

Residual Noise Measurement

(10Hz-80kHz)

Power requirements 9 Watts

Dimensions HxWxD = 8.6" x 1.75" x 11"

5Hz(-0.25dB) to 68kHz(-0.5dB)

2Hz(-.25dB) to 149kHz(-3dB)

10Hz(-0.25dB) to 68kHz(-0.5dB)

10Hz(-.25dB) to 148kHz(-3dB)

-89 dBu

(218mm x 44mm x 280mm)

Shipping weight Approximately 7 lbs (3.2Kg)

ALL MEASUREMENTS WERE PERFORMED WITH AN AUDIO PRECISION TEST SET .

Chapter 1 Introduction Section 4

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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 EQF 810. The proper installation of the EQF 810 as part of a larger
system requires a clear understanding of audio wiring, AC distribution,
grounding, and shielding techniques.

When the EQF 810 is being installed into a larger system, it may be
necessary to retain the services of someone experienced in these
matters.

The EQF 810 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 dealer or 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.

To insure adequate airflow around the unit and to prevent overheating,
do not obstruct the air vents on the side and top.

While the internal circuitry of the EQF 810 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.

Chapter 2 Installation Section 6

Grounding the product

Mechanical installation

The ground pin of the power cord and power inlet are internally
connected to the chassis. To avoid electrical shock, plug the EQF 810
into a properly wired AC receptacle. For safety reasons, do not lift the

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

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.

The location of the EQF 810 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 EQF 810 allows a single unit to be
mounted on a table top with the (4) rubber bumpers (supplied), multiple
units stacked, or two units mounted side-by-side on a 1U rack shelf.

1 rack space (1U) rack shelves are manufactured by:

Physical placement of

adjacent equipment

• Middle Atlantic Products, Model UTR1

• Raxxess, Model UNS1.

When attaching the EQF 810 to the rack shelf, it should be secured with
(3) 6-32 x ½” machine screws (supplied). Do not use screws that are
longer than ½” in length as they could damage the internal circuit
board. When a single or multiple EQF 810’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.

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 EQF 810 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 should be located
away from the EQF 810 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 and rear panels are a high quality painted surface and the
panel lettering is applied using a silkscreen printing technique.

To clean the front or rear panel, wipe the surface gently using a soft
lint-free 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.

The following information is provided as a general guide for
repackaging your EQF 810 for shipment. If you have any questions,
contact Speck Electronics at [phone].

If the product is to be shipped to Speck Electronics for service or repair,
contact Speck Electronics for a Return Merchandise Form. When we
receive the completed form, a RMA number and shipping instructions
will be issued. Place the product in the original container if available.

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

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Chapter 3 Operation Section 9

Operation

General

Basic Theory

of Equalizers

Low-pass filter

We hope to give you basic information on the operation of the EQF 810
and adequately describe its controls, switches, and connectors.

The information in this manual is intended to help with the technical
process when using your equalizer. Words alone could not adequately
describe how to adjust the controls of an equalizer. Your ears should be
your best gauge of how to adjust the equalizer controls to make the
sound fit your requirements.

A parametric equalizer falls into the generic category called a “filter.”
A filter is an electronics circuit that allows signals of certain frequencies
to be transmitted through a system, while preventing the transmission
of other frequency ranges.

There are 3 basic types of passive or active filters; low-pass, high-pass,
and bandpass.

A low-pass filter is a circuit that passes all low frequency signals and
rejects high frequency signals. The crossover point that low
frequencies pass through can be either fixed at a specific point or
variable.

High-pass filter

Bandpass filter

A high-pass filter is a circuit that passes all high frequency signals and
rejects low frequency signals. The crossover point that high
frequencies pass through can be either fixed at a specific point or
variable.

A bandpass filter is a circuit that will pass only a fixed frequency band
and reject signals above and below the selected band.

A parametric equalizer is a very elaborate bandpass filter that offers the
ability to control the filter's basic parameters - hence the term
“Parametric Equalizer.” These controllable parameters are the
bandpass center frequency, the amplitude of the bandpass frequency,
and the width of the bandpass frequency. These previously mentioned
parameters as found on audio parametric equalizers are commonly
known as the sweep control, boost/cut control, and bandwidth (Q)
adjust respectively.

The EQF 810 equalizer utilizes all the previously mentioned parametric
controls.

Chapter 3 Operation Section 10

Default Control Settings

Before any attempt is made to operate the EQF 810, 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.

All “Frequency Sweep” and “Bandwidth” controls should be set to their
full counter-clockwise setting. All “Boost/Cut” 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
EQF 810, will be assumed that they have been set to their neutral
positions.

Chapter 3 Operation Section 11

FRONT PANEL CONTROLS

1. Output Select

VARIABLE FILTERS

2. High Pass Frequency

3. High Pass Filter Enable

This switch will select either a “Transformer­Balanced” or “Active-Balanced” output for the XLR
and 1/4” TRS outputs.

A dual colored LED will illuminate indicating that the
EQF 810 is powered and active. When the output
switch is set to the “XFMR” position, the LED will
indicate green. This LED will change from green to
red when the switch is depressed to the “ACTIVE”
position.

This control adjusts the frequency of the HP filter from 20Hz (Full
CCW) to 250Hz (Full CW) with a slope of 12dB/octave for the low

range selection or 100Hz to 1.2kHz when the 5X select switch is
enabled.

This switch is used to enable or disable the High
Pass filter circuit. In the “out” position, this switch

5

completely bypasses the HP filter circuitry. When
this switch is depressed, the HP filter is enabled.
A green LED indicates the operation of the filter.

1

6

4. High Pass X5 select

This switch selects the frequency range of the high
pass filter. In the “out” position, the low range of
20Hz-250Hz is selected. When depressed, this
switch selects a range of 100Hz-1.2kHz. A yellow
LED illuminates indicating that the 5X frequency
multiplier has been enabled.

5. Low Pass Frequency

This control adjusts the frequency of the LP filter
from 150Hz (Full CCW) to 25kHz (Full CW) with
a slope of 12dB/octave.

6. Low Pass Filter Enable

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

3

4

2

Chapter 3 Operation Section 12

7. Equalizer bypass switch

L (Low) BAND

8. Low frequency sweep

9. Low boost/cut

This switch is used to enable or disable the 4 band equalization circuit.
In the “out” position, all equalizer bands are bypassed. When in the
bypass position, the active balanced input stage, the active balanced
output stage, and the transformer remains operational. This allows the
levels to match when comparing the equalized signal to the unequalized
signal. A green LED indicates the operation of the equalizer.

The low frequency sweep control is used in conjunction with the low
boost/cut control and provides continuous
adjustment of the center frequency from 20Hz
(fully counterclockwise) to 400Hz (fully

8

clockwise). The Bandwidth (Q) of the low band
is fixed at 1 octave (Q=1.0)

The boost/cut control provides a reciprocal
volume adjustment of the selected frequency
control. This means that whatever frequency is
“boosted” with the boost/cut adjusted from its
center position clockwise, an identical but
opposite result is achieved when that same
frequency selection is “cut” from its center
position counterclockwise. Once the desired
frequency has been selected with the low

7

frequency sweep control, that frequency may be
continuously accentuated or attenuated (boost or
cut) from 0 to +15dB or -15dB. 0dB (flat) is obtained when this control
is set to its center detented position.

10

9

10. Peak/Shelf Switch

This switch changes the low frequency band from a peak/dip curve (as
shown in Figure 1a) to shelving curve (as shown in Figure 1b).
.

Fig. 1a. Shelving Curve

Fig. 1b. Peak/Dip Curve

Chapter 3 Operation Section 13

L/M (Low/Mid) BAND

11. Low/Mid frequency sweep

12. Low/Mid X10 select

13. Low/Mid Boost and cut

14. Low/Mid bandwidth adjust

The low/mid frequency sweep control is used in conjunction with its
respective boost/cut control and provides continuous adjustment of the
center frequency from 40Hz (fully counterclockwise) to 800Hz (fully
clockwise) for the low range selection or 400Hz (fully
counterclockwise) to 8kHz (fully clockwise) for the mid range
selection.

This switch selects the frequency range of the Low/Mid band. In the
“out” position, the low range of 40Hz-800Hz is selected. When
depressed, this switch selects the mid band of 400Hz-8kHz. A yellow
LED illuminates indicating that the 10X frequency multiplier has been
enabled.

This control provides 15dB of bell shaped
boost or cut for the Low/Mid band frequency

11

14

range, and is used in conjunction with the
Low/Mid frequency sweep adjust. 0dB (flat)
is obtained when this control is set to its
center detented position.

For the Low/Mid band, a continuously
adjustable bandwidth control is provided.
This control sets the width of the frequency
that has been selected on the Low/Mid
sweep control. When set fully CCW, the
bandwidth is a wide 2.25 octaves (Q=.45).
When set fully CW, the bandwidth narrows
to .22 octave (Q=4.4). The center position

12

13

is approximately .4 octaves (Q=2.4).

In addition to the ability to contour low band audio, the low frequency
controls may be used to reduce or eliminate low frequency hum or
buzz. Low hum is typically 60Hz, whereas buzz is typically 120Hz and
240Hz. If there is a hum or buzz on an audio track, the low sweep
control and associated boost/cut control can be used to remove this.

To reduce 60Hz hum, start by setting the bandwidth control to its fully
(CW) position, the low frequency sweep control to its fully
counterclockwise (CCW) position; this is about 40Hz. Turn the
Boost/Cut control fully CCW. Return to the frequency sweep control,
and turn clockwise a little until the 60Hz hum has been reduced. This
setting is the 60Hz point. Now go back to the Boost/Cut control and
adjust as necessary.

In some extreme cases, it may be necessary to use both the low band
and the Low/Mid band of equalization in order to remove the
undesirable affects of 60Hz or 120Hz hum.

Chapter 3 Operation Section 14

M (Mid) BAND

15. Mid frequency sweep

16. Mid boost/cut

17. Mid bandwidth adjust

The mid frequency sweep control is used
in conjunction with the mid boost/cut
control and provides continuous

15

adjustment of the center frequency from
400Hz (fully counterclockwise) to 10KHz
(fully clockwise).

This control provides 15dB of bell shaped
boost or cut for the Mid band (400Hz to
10kHz) frequency range, and is used in
conjunction with the high frequency sweep
adjust. 0dB (flat) is obtained when this
control is set to its center detented
position.

17

For the Mid band, a continuously adjustable bandwidth control is
provided. This control sets the width of the frequency that has been
selected on the Mid sweep control. When set fully CCW, the
bandwidth is a wide 2.25 octaves (Q=.45). When set fully CW, the
bandwidth narrows to .22 octave (Q=4.4). The center position is
approximately .4 octaves (Q=2.4).

16

H (High) BAND

18. High frequency sweep

The high frequency sweep control is used in
conjunction with the high boost/cut control
and provides continuous adjustment of the
center frequency from 1.5kHz (fully
counterclockwise) to 25kHz (fully
clockwise). The Bandwidth (Q) of the High
band is fixed at 1 octave (Q=1.0)

.

18

20

19

Chapter 3 Operation Section 15

19. High boost/cut

20. Peak/Shelf Switch

This control provides 15dB of bell shaped boost or cut for the high
frequency range (1.5kHz to 25kHz), and is used in conjunction with the
high frequency sweep adjust. 0dB (flat) is obtained when this control is
set to its center detented position.

In addition to the ability to contour high band audio, the high band
controls can reduce hiss that is present on low frequency information. If
there is high frequency hiss or digital noise on a kick drum or bass
track, the high sweep control may be set to its higher clockwise setting
(16kHz-25kHz) and its associated boost/cut control “cut” a few dB's.
As long as you don't dramatically change the sound of the low
frequency audio, this could remove a little noise. Every little bit
improves the overall quality of your sound.

This switch changes the high frequency band from a peak/dip curve (as
shown in Figure 2a) to shelving curve (as shown in Figure 2b).

Fig. 2a. Shelving Curve

Fig. 2b. Peak/Dip Curve

Chapter 3 Operation Section 16

REAR PANEL

21. Input Connectors

22. Output Connectors

22

21

Two types of input connectors are available on the EQF 810: a 1/4”
TRS balanced jack and a female XLR connector. These inputs are
internally wired in parallel and identical in every aspect except for the
connector.

The input 1/4” TRS and XLR should not be used at the same time.

The 1/4” jack will accept a balanced TRS plug or a unbalanced mono
TS plug. For unbalanced operation a standard mono plug should be
used.

The output of the EQF 810 has a balanced 1/4” jack and male XLR
connector. These outputs are internally wired in parallel and there is no
operational difference between one or the other. The outputs can be

either “Transformer-Balanced” or “Active-Balanced” depending on the
position of the “Output Select Switch” on the front panel.

The 1/4” TRS and XLR may be used at the same time.

The pin configuration for all XLR connectors are:

The pin configuration for all ¼” TRS jacks are:

HIGH

LOW

GROUND

HIGH

LOW

GROUND

PIN 2
PIN 3
PIN 1

TIP

RING

SLEEVE

Chapter 3 Operation Section 17

24

23. A.C. Power inlet

24. Fuse

23

25

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

The EQF 810 power supply operates at mains voltages of 100-120 for
the Model EQF 810-NA or 220-240 for Model EQF 810-EU. The
mains voltage is set at the factory and marked accordingly on the rear
panel.

The ground (Earth) pin of the power inlet is internally connected to the
chassis. For safety reasons, do not lift the ground (Earth) 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 (T) type fuse. To avoid the risk of fire, always replace the
fuse with the correct value fuse as marked on the rear panel; .750 amp
for the 120V model, or .375 amp for the 230V model.

25. Power Switch

This ON/OFF power switch applies AC (mains) power to the EQF 810.

100 VAC

.750 Amp .750 Amp .375 Amp .375 Amp

120 VAC 220 VAC 230 VAC 240 VAC

Fuse Chart

.375 Amp

Figure 3.

Chapter 3 Operation Section 18

26. Mains Voltage
Selector Switch

If it becomes necessary to change the mains voltage, there is a voltage
selector switch inside the EQF 810. The cover must be removed to gain
access to the selector switch.

Always remove the power cord from the power inlet (#23) before
changing the 115/230 voltage selector.

Take the cover off by removing (6) phillips screws on the sides of the
cover, and remove (5) phillips screws on the back of the cover. Do not
remove any other internal mounting screws.

Take the cover off and you will see a slide switch mounted on the green
circuit board as shown in Figure 4. Beside the switch (#26) are
markings in white letters: 115-------230.

If your mains voltage is 100VAC or 120VAC, set the voltage selector
switch to the “115” position.

If your mains voltage is 220VAC, 230VAC or 240VAC, set the voltage
selector switch to the “230” position.

Replace the cover and change the fuse according to the chart shown in
Figure 3, on Page 17.

It is recommended that you
remove the factory marking in
the small square box below the
serial number with a solvent
and re-mark the box so it

26

indicates the proper operating
voltage.

Figure 4

Chapter 4 Wiring and Other 19

Wiring and Other

General

Start simple

The following information is not specific to the operation of the
EQF 810, 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
product 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 EQF 810, 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 EQF 810
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 EQF 810 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 recommendations when
selecting cable and connectors.

Chapter 4 Wiring and Other 20

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 equalizer 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

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.

Safety earth connection

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. 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 (220,
230, 240 in Europe)

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Electronics earth

Proper Audio

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,” it
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.

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 EQF 810.
EMI is defined as any unwanted signal which adversely affects the
operation of 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.

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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 computers, samplers, and magnetic
field sources from transformers and power supplies.