Focusrite ISA428 MkII User manual

User Guide
focusrite.com
FA0438-03
Four channel mic pre and optional A-D card with Dante
ISA428
MkII

2
CONTENTS
About this User Guide .....................................................................3
INTRODUCTION ..............................................................................4
ISA 428 MKII CONTROLS AND FEATURES ....................................................5
Front Panel ................................................................................5
Input Channel Controls ....................................................................5
Input Selection..........................................................................5
Mic Input Gain ..........................................................................5
Line Input Gain .........................................................................5
Instrument Input........................................................................6
Z In (Input Impedance)...................................................................6
+48V ...................................................................................6
Phase ..................................................................................6
Filter...................................................................................6
Insert ..................................................................................6
Channel Meters............................................................................7
A-D Card Clock and Sync Switches.........................................................7
Rear Panel ................................................................................8
AC Mains Inlet ..........................................................................8
Channel Mic Inputs......................................................................8
Channel Line Inputs .....................................................................8
Channel Outputs ........................................................................8
A-D Inputs 5–8..........................................................................8
Channel Insert Sends & Returns .........................................................8
A-D Option Card Slot ....................................................................8
A-D Option Card ...........................................................................9
PHYSICAL CHARACTERISTICS ..............................................................10
Power Requirements .....................................................................10
APPENDICES ................................................................................ 11
1. Connector Pinouts...................................................................... 11
2. Preamp Input Impedance ..............................................................13
3. Pro Tools Interfacing ...................................................................15
PERFORMANCE AND SPECIFICATIONS .....................................................16
Focusrite Pro Warranty and Service ......................................................18

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About this User Guide
This user guide applies to the ISA 428 MkII mic pre. It provides information about installing and using
the unit, and how it can be connected into your system.
Also included is information relating to the optional ISA ADN8 A-D interface card, which will allow
audio from the Mic pre to be added to a Dante network.
If you feel that additional information might be of assistance, be sure to consult the site:
pro.focusrite.com/technical-support, which contains a comprehensive collection of common
technical support queries.
Pro Tools® and Pro Tools | HDTM are trademarks or registered trademarks of Avid Technology, Inc. or its subsidiaries
in the United States and/or other countries.
Dante® and Audinate® are registered trademark of Audinate Pty Ltd.
Box Contents
• ISA 428 MkII unit
• AC power lead
• Safety information cut sheet

4
INTRODUCTION
Thank you for purchasing the Focusrite ISA 428 MkII.
The ISA 428 MkII is a high quality four channel microphone preamplier, which can be used to record
microphone, line-level or instrument sources. Microphones and line-level sources are connected via
the rear panel, whilst instrument inputs can be plugged directly into the front panel jack sockets.
The front panel also features gain and other settings such as phantom power and impedance for
each of the analogue inputs. LED metering is provided on each channel in dBFS, to indicate when the
level is reaching the digital clipping point.
To maintain pristine Focusrite quality in the digital domain, an Analogue-to-Digital interface card
may be tted into the option slot on the rear panel. This provides access to a Dante network and
features AES3, S/PDIF and ADAT signals.
With the A-D card installed, the internal/external clock sample rate and sync source can be selected
using the switches on the front panel.

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ISA 428 MKII CONTROLS AND FEATURES
Front Panel
Applies +48V phantom power to the
mic input XLR
Inverts polarity (Phase) of the
selected input
Input Trim pot Mic/Line: 0 +20 dB
Instrument: +10 +40 dB
Applies the variable-frequency high-
pass Filter to the selected input
Filter frequency pot
Z In selects the input impedance for
the Mic and Instrument inputs
Switches the external Insert
return into the channel path
Input source selection
Selects the high (30-60 dB) mic
gain range for the Gain switch
10 dB stepped Mic/Line Gain switch
Mic: 0-30 / 30-60 Line: -20 +10
Input Channel Controls
Input Selection
Each press of the Input button steps through the three available input sources: Mic/Line/Instrument.
Mic Input Gain
The Gain switch adjusts the mic gain in three 10 dB steps. Its range is either 0–30 dB or 30–60 dB
when the 30–60 switch is pressed. An additional 0–20 dB of continuous gain adjustment is available
using the Trim control.
To avoid an excessive jump in level, It is recommended that the stepped Gain switch is turned to minimum before
pressing the 30-60 switch.
Before starting a recording, or if used for PA work, set the Trim control to near its centre position.This will allow for
some gradual gain adjustment up or down without the use of the stepped control.
Line Input Gain
The Gain switch adjusts the gain between -20 dB and +10 dB in 10 dB steps. Continuous gain
adjustment of up to 20 dB can be added using the Trim control.
Input channels
Power
switch
Instrument
inputs
LED
meters
A-D option card:
clock and sync
selection

6
Channel Controls...
Instrument Input
The Instrument inputs are accessed via standard 1/4” mono jacks on the front panel. The level is set
using the Trim control only and is continuously adjustable from +10 dB to +40 dB.
Refer to the appendix on page 11 for connector pinouts.
Z In (Input Impedance)
With Mic input selected, pressing the Z In button steps through the four
transformer preamp input impedance options. The values are shown in the
table.
For additional information on impedance selection see Appendix 2, “Preamp Input
Impedance” on page 13.
With Instrument input selected, pressing the switch toggles between High
and Low impedance settings, as shown in the lower table.
The Line input impedance is xed at 10 kΩ and is not affected by the Z In
switch.
+48V
Pressing the +48V button applies phantom power to the Mic input XLR.
This switch does not affect the Line or Instrument inputs.
If you are unsure whether your microphone requires phantom power please refer to its handbook. Certain
microphones (most notably ribbon and unbalanced mics) could be damaged by applying phantom power.
Phase
Pressing Phase inverts the polarity of the selected input. This can be useful when multiple mics are
used in close proximity (ie., on a drum kit).
Filter
Pressing the Filter button inserts the 18 dB/octave high-pass lter into channel path; it is applied
to whichever input is selected. The High Pass Filter control allows the roll-off frequency to be set
within the range 16 Hz to 420 Hz.
The lter is useful for removing any unwanted low frequencies, eg., rumble transmitted through oor mounted
mic stands, etc.
Insert
Pressing Insert places the Insert Return signal into the channel path before the Output connector,
allowing the inclusion of external effects units.
The Insert Send is always available and is post the input Gain and Filter controls.
Low 600 Ω
ISA 110 1.4 kΩ
Med 2.4 kΩ
High 6.8 kΩ
Low 470 kΩ
High 2.4 MΩ
Mic Impedance
Instrument Impedance

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Channel Meters
The front panel LED meter groups 1–4 and 5–8 display the audio level at two
different locations:
• Meters 1–4 display the signal level at the channel outputs.
The channel outputs are also routed to inputs 1-4 of the A-D option card.
• Meters 5–8 display the signal levels received at A-D Input connectors 5–8
The LED meters, therefore, always indicate the input levels at the A-D option card
prior to conversion.
The meter scales are in dBFS, ie., the level in dB, relative to maximum output
(reached when the red ‘0’ LED illuminates). ‘0’ indicates a level of 22 dBu which
corresponds to the maximum input level of the A-D card.
A-D Card Clock and Sync Switches
Clock select
Allows the user to select the internal sample frequency: 44.1kHz, 48kHz, 88.2kHz,
96kHz, 176.4kHz, or 192kHz.
Ext
Allows the ISA ADN8 A-D card to follow an external Word Clock source. Press the switch
to toggle between standard and Dante clock.
Lock LED
Indicates that the unit is successfully synchronised to the external Word Clock.

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AC Mains Inlet
Standard IEC receptacle for AC mains. ISA 428 MkII features a ‘Universal’ PSU, enabling it to operate
on any supply voltage between 100 V and 240 V AC.
Channel Mic Inputs
Four latching XLR-3 female connectors.
Channel Line Inputs
Four balanced 1/4” TRS jack sockets.
Channel Outputs
Four XLR-3 male connectors. The outputs are connected to inputs 1–4 of the A-D option card.
A-D Inputs 5–8
XLR-3 female analogue inputs to channels 5–8 of the A-D option card.
These inputs have no function without the optional A-D card installed – however, LED meters 5–8 will still
indicate the incoming signal levels.
Channel Insert Sends & Returns
Analogue sends and returns on XLR-3 male and female connectors.
The return signal can be added into a channel path by pressing the front panel Insert switch.
A-D Option Card Slot
Slot for ISA ADN8 analogue to digital conversion card. See the following page for card details.
The card allows the audio outputs from the ISA 428 MkII, plus the four additional external inputs, to
be added to a Dante network. It also provides AES3, S/PDIF and ADAT signals.
See Appendix 1 on page 11 for connector pinouts.
Rear Panel
Mic inputsLine inputs
Insert Sends
& Returns
Channel
Outputs
Mains
inlet
A-D external
inputs 5-8
Slot for A-D
option card

9
A-D Option Card
The optional ISA ADN8 A-D card can be retrotted to an ISA 428 MkII at any time. Engineering
experience is not required as the card can easily be installed by the user.
Note that the ISA 428 MkII does not support the earlier ISA 8-Channel A-D card.
Once tted, conguration of the card is carried out over the network using either RedNet Control or
the Dante Controller software application.
The tting instructions and network software applications are included with the A-D card option.
Word Clock – Input
Allows the card to be synchronised to an external Word Clock source via the BNC connector.
Word Clock – Output
Provides an output of the external Word Clock source connected at the “Word Clock In” BNC connector
or, transmits the internal sample frequency of the A-D card.
• When the ISA 428 MkII is following other units within a larger digital system, the Word Clock
Out connector can be used to pass on the Word Clock signal to the next device.
• When the unit is not following another device and is in Internal Clock mode, the Word Clock
Out connector outputs the sample frequency selected on the ISA 428 MkII front panel.
Primary Network Port
Latching RJ45 connector for the Dante network. Use standard Cat 5e or Cat 6 network cable to
connect the ISA ADN8 to a local Ethernet switch which is connected to the Dante network. Adjacent
to each network socket are LEDs which illuminate to indicate a valid network connection and network
activity.
Secondary Network Port
Can be used as the Secondary Dante network connection where two independent Ethernet links are
being used (Redundant mode), or an additional port on an integral network switch on the primary
network (Switched mode).
ADAT 1 and 2
Two ADAT optical outputs using standard Toslink connectors. Provides 8 channels at 96kHz (using
S/MUX II). The ADAT channel count halves with every doubling of Sample Rate.
AES3 Outputs 1-8
Eight AES3 outputs on DB25 connector. The connector is wired to the Tascam digital standard.
See Appendix 1 on page 11 for the connector pinouts.

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Case dimensions are illustrated in the diagram above.
ISA 428 MkII requires 2U of vertical rack space. Allow an additional 75mm of rack depth behind the
unit to allow for cables. ISA 428 MkII weighs 7.05 kg and for installations in a xed environment (eg.,
a studio rack), the front-panel rack mountings* will provide adequate support. However, if the unit
is to be used in a mobile situation (eg., ight-cased for touring, etc.), it is recommended that side
support rails or shelves are used within the rack.
*Always use M6 bolts and cage nuts specically designed for 19” equipment racks. An Internet search using the
phrase “M6 cage nuts“ will reveal suitable components.
Cooling vents are provided at each side; ensure that when mounted in a rack these vents are
not obstructed. Do not mount the unit immediately above any other equipment which generates
signicant heat, for example, a power amplier.
Note.The maximum operating environmental temperature is 40°C / 104°F.
Power Requirements
ISA 428 MkII is mains powered and incorporates a ‘Universal’ power supply which can operate on
any AC mains voltage from 100 V to 240 V. The AC connection is via a standard 3-pin IEC connector
on the rear panel.
A mating IEC cable is supplied with each unit – this should be terminated with a mains plug of the
correct type for your country.
Power consumption for ISA 428 MkII is 35 W.
Please note that there are no fuses or other user-replaceable components of any type in any unit.
Please refer all servicing issues to the Customer Support Team (see “Customer Support and Unit Servicing”
on page 18).
PHYSICAL CHARACTERISTICS
465.0mm / 18.3”
325.0mm / 12.8”
63.6mm / 2.5”