products -
The industry standard for signal processing
The legendary Forte recording console,
still regarded by many as the most
sonically impressive analogue console
ever created.
The last word in quality from the first name in audio
Mention the name “Focusrite” to anyone in the music recording
industry and you are likely to observe immediate recognition and
appreciation of the high sonic values that recording professionals
attribute to our products. After all, they have become permanent
fixtures in most of the top recording studios the world over, as well
as finding pride of place in the personal studios of many leading
engineers and producers.
The Focusrite brand was established in
1985 and quickly became recognised as
the source of the best outboard
equalisers, compressors and microphone
preamplifiers money could buy. Focusrite
set the trend for the use of these
outboard devices in the world’s finest
studios with the realisation that even the
most technically sophisticated recording
consoles lacked the sonic qualities of
boutique outboard processors. The
design heritage was built around the ISA
110, a microphone preamplifier and
equaliser module designed initially for the
custom console at AIR Studios, London.
This classic transformer-based design has
been the cornerstone of all the classic
Focusrite products.
The extended bandwidth and low
distortion characteristics of the ISA and
Red range created the ultimate
Microphone interface and helped to bring
out the best in both the microphone and
the performer. The circuit implementation
harked back to the Hi/Lo controls on the
simple EQ sections of early solid state
consoles, and no other EQ represented
the classic EQ sound quite like this
switched capacitor circuit. The signature
of this EQ is the classic open sounding
HF boost (bringing e.g. reverb tails to life),
and surgical yet flexible parametric high
mid and low mid, as well as thick
powerful bass control from the LF section.
The ISA110 was offered in racks of up
to eight modules and was the foundation
product for the new brand. More recently,
the ISA 110 was re-released as a limited
edition classic, and serial 001 was
presented to Sir George Martin in
recognition of our unique association with
AIR studios. The ISA 110 was incorporated
into the Focusrite Studio Console launched
in 1990 to critical acclaim.
In 1993 the ISA 215 incorporating two
ISA 110’s in a 19” rack-mount package
was introduced, and rapidly became the
industry standard dual EQ. To partner the
original ISA 110 in the 1980’s, the ISA
130 compressor was designed, utilising a
proprietary VCA designed by Trevor
Stride (Trevor is still designing for
Focusrite and is our technical “guru”).
The design provided the signature Soft
Knee compression for which Focusrite
has become known, adding punch and
power without distortion or colouration.
George Martin with the ISA110 re-issue.
With the current ISA products, this mic pre and EQ circuit
remains a timeless classic amongst the world’s top
producers and engineers.
Producer Pack
The pinnacle of Focusrite’s Channel strip technology
page 4
ISA 430 MK II Applications
Diagrams explaining the unmatched flexibility of the
ISA 430 MK II Producer Pack
page 6
A-D conversion
Award-winning 192 kHz Analogue to Digital
conversion from Focusrite
page 7
ISA 428 Pre Pack
A unique blend of four classic vintage analogue mic
pre’s with state-of-the-art 192kHz digital technology
page 8
ISA 220 Session Pack
A channel strip designed to provide the engineer
with all the classic Focusrite modules required to
record a session with uncompromised quality
page 10
With this proprietary design, frequency
response remains natural and controlled,
even with large amounts of gain reduction
applied. From the creation of these
fundamental building blocks, and with new
innovations from Trevor Stride and
Focusrite’s Director of Product Strategy,
Robert Jenkins, Focusrite have gone on to
create a whole host of analogue signal
processing outboard to fulfil the
demands of today’s professional audio
recording engineers.
We hope you find the information
contained in this brochure useful, but
the best way to really learn about our
products is to audition them for yourself.
Please contact your local Focusrite
dealer for further information, and a
hands-on demonstration.
Red 1 Quad Mic Pre
Four channels of Focusrite’s legendary mic pre amps
page 12
Red 2 Dual Equaliser
Powerful and responsive equaliser with Focusrite’s
much sought-after warmth and smoothness
page 14
Red 3 Dual Compressor/ Limiter
The first choice of the world’s leading producers
and engineers
page 16
The Liquid Channel
Every mic-pre and compressor in history, nailed
page 17
Red 7 Mic Pre & Dynamics
Powerful and versatile tracking processor including a
mic pre, compressor, de-esser and exciter
page 18
Phil Dudderidge, Chairman
Focusrite Audio Engineering
ISA 430 MKII: Producer Pack
The ISA 430 MKII represents the pinnacle of Focusrite’s analogue channel strip technology,
bringing together all the classic designs in one comprehensive production tool. Augmented with
additional features and flavours, alongside unmatched internal routing and connectivity, the ISA
430 MKII enables today’s recording professional to enjoy the unique sonic contribution of these
heritage designs within one extremely versatile processor. Focusrite’s iconic status as the
leading manufacturer of channel strips remains unrivalled.
Classic Focusrite transformer-based Mic-pre with variable
impedance and ‘Air’ feature
Classic Focusrite EQ design; an expanded version of the
original ISA 110
Multi format Compressor; switch between Focusrite’s
transparent VCA circuit and a vintage optical circuit
Post mic pre output for the shortest possible signal path
Unmatched flexibility with an incredible variety of insert points
and variable signal path arrangements
Ability to function as 4 separate modular processors: mic pre, EQ,
Dynamics and stereo ADC
Precision VU metering of input level, Insert 1 or 2 Return level,
Compressor gain reduction or Sidechain listen level (switched)
Proprietary Focusrite discrete Class A VCA Gate and
Expander designs
‘Listen’ feature for precise control over compression, gating,
expansion and de-essing
De-esser design based on optical technology for lower distortion
and transparency
Soft Limiter to avoid critical digital overload
Optional Stereo A/D – 24-bit 192 kHz Delta Sigma converter
The input section on the ISA 430 MKII
features a large, professional-grade VU
Meter with adjustable calibration, which
can be selected to display any one of a
number of multiple points in the signal
chain. Additional visual monitoring is
available through the inclusion of two LED
bar graph meters, allowing the signals
being fed to the input and output of the
unit, or the ADC input levels to be viewed.
As with the ISA 428, the ISA 430 MKII has
a variable impedance option on its classic
transformer-based Mic-pre, ranging from
600 to 6800Ω (at 1kHz). This provides the
engineer with increased control over the
interaction between microphone and preamp, tailoring the response to suit his or her
needs. Pressing the ‘Air’ switch further
extends this principle, introducing an
inductor circuit into the secondary of the
transformer, which adds clarity and
‘spaciousness’ to the signal without the
need for EQ.
The split configurable Inserts and
changeable signal path order combine to
produce an unrivalled flexibility; herein lies
the real benefit of the ISA 430 MKII as a
‘do-all’ processor for the most demanding of
engineers. Both Inserts can be used to
separate the individual sections of the
channel strip. This means that if the postmic output and ADC inputs are in use, the
ISA 430MKII can function as four discrete
processors simultaneously! (EQ and
dynamics split mode; see diagram on
page 6). Insert 2 can also be located postdynamics should this be required, and for
further adaptability, the dynamics can be
shifted to a pre-EQ or post-sum position.
A significant development from the original
ISA 430 can be found in the Compressor
section, which now boasts a vintage opto
circuit in addition to the original discrete
Class A VCA design. Selecting the optical
Compressor or Limiter results in a more
coloured sound, as opposed to the
extremely transparent VCA circuit. The ISA
430 MKII caters for the most varied of
signals, containing an ‘Auto Release’
function (switch activated) that changes the
release time with each transient to suit the
nature of the waveform. If the signal sounds
excessively processed, a remedy lies in the
Compressor ‘Blend’ feature, allowing the
pre- and post-dynamics signals to be mixed.
This can help restore a track’s natural
dynamism without losing the desired effect
of compression.
The ISA 430 MKII features the same
classic Focusrite EQ as the original ISA 110,
but with two extra frequency values for
both the high and low shelving, and with
the added benefit of being able to insert the
EQ into the sidechain of the Compressor
and Gate sections. This allows for fully
frequency-conscious compression, gating
and expansion, making the ISA 430 MKII
the most powerful dynamics processor
yet developed.
The Gate section uses the Focusrite Class A
VCA as the control element to remove the
effect of unwanted interference and high
levels of wide-band system noise build-up.
I S A 4 3 0 M K I I S P E C I F I C AT I O N S
Gain Range:
Input Impedance:
Gain Range:
Input Impedance:
+10dB to +40dB continuously
0 to +60dB in 10dB steps
Variable as follows:
600Ω, 1400Ω, 2400Ω, 6800Ω
-128dB with 150Ω terminating
impedance at 60dB of gain
0.001% with -20dBu
1kHz input and 20Hz–22kHz
bandpass filter
Compressor (VCA mode)
Threshold Range:
-28dB to +12dB
1.5:1 to 10:1
Soft knee
100µS to 100mS
100mS to 7S, variable or
auto (program dependent)
Soft knee in Comp mode,
Hard knee in Lim mode
Threshold Range:
Gate Range:
Expander Ratio:
-40dB to +10dB
0 to -80dB
switched fast or slow
100mS to 5S
20mS to 4S
0 to 5:1
Threshold Range:
Frequency Range:
Ratio at centre
Limiter Threshold
2K2 to 9K2
infinite (Brick Wall)
Frequency dependent
Compressor (Vintage Opto mode)
Threshold Range:
-28dB to +12dB
1.5:1 to 5:1 in Comp mode
5:1 to 20:1 in Lim mode
Switching this section to expand mode
causes the Gate to function as an Expander.
Instead of cutting off any signal below the
threshold, an expander proportionately
decreases it. This provides a more natural
sound when reducing noise from
non-percussive sources (especially vocals).
‘Hysteresis’ increases the level-difference
between the gate switching on and
switching off, and prevents the gate
oscillating (‘chattering’) with particular
combinations of input signal and threshold
settings. This function is particularly useful
when gating a signal with a very long decay
time and large amounts of level modulation
(for example a Grand Piano).
All four dynamic processors; the
compressor, gate, expander and de-esser,
feature Focusrite’s unique ‘Listen’ feature.
Selecting ‘Listen’, inverts the operation of
the processor, so only the chosen
frequencies that are being affected can be
heard, rather than straining to hear the
overall effect in a complex signal.
The optional stereo A/D card provides the
ISA 430 MKII with 24-bit 192kHz
capabilities and employs the same
converters as those featured in the TEC
award nominated ISA 428. (For more
information, see the ADC details overleaf.)
The sensitively designed soft Limiter, also
present in the ISA 428, can be made to act
on both the analogue output and the inputs
to the optional ADC. The gradual changes
in ratio leading up to 0dBFS produce a
gentler limiting effect whilst still preventing
a level overload.
The ISA 430 MKII’s De-esser is based on a
low-distortion optical technology
design, allowing transparent
removal of excessive sibilance
from a vocal performance. The
circuit uses phase cancellation to
create a smoother and less
intrusive de-esser than traditional
compression-based designs.
ISA 430 MKII: Applications
Split ‘mixdown mode’
This example shows how to use the ISA 430 MKII in split
mode as a mixdown tool. The unit has been switched to both
‘EQ split’ and ‘Dyn split’, and connected to two channel
inserts of a mixing console. One is used to EQ, the other as a
dynamics processor. The stereo mix is then converted using
the ISA 430 MKII’s ADC and soft Limiter for high quality
digital mastering.
Record channel
This example shows the ISA 430 MKII being used for mic or
guitar recording. The Insert points may be used to add
external processing ‘in-line’ if required.
Using the ISA 430 MKII
as four discrete units
This example shows how to use the ISA 430 MKII as four
individual processing units. This unit is switched to ‘EQ split’
AND ‘Dyn split’, and ADC Inputs 1 & 2 are switched on. The
unit is simultaneously allowing equalisation, plus separate
dynamics processing of audio. At the same time, it is
permitting two channels of A/D conversion into a DAW, as
well as allowing super clean microphone recording!
Split + digital record mode
This example shows an analogue input connected to Insert
Return 1 and then routed, via EQ modules, to Insert Send 1,
which then feeds ADC Input 1. A second analogue input is
connected to Insert Return 2 and then routed, via the
dynamics module, to Insert Send 2, which then feeds ADC
Input 2. This allows two separate sources to be processed
and recorded via the digital output.
A-D Conversion
Just paying for the PCB and circuitry,
One of the most important aspects of
without any additional casing and
the ADC is the clock design, as this
metalwork, affords a considerable
determines the linearity of the digital
reduction in cost whilst maintaining an
output. All Focusrite ADCs are designed
extremely high level of sonic clarity.
to have incredibly low jitter figures
However, the benefits from installing
(44.1kHz-192kHz < 20 psec) which
Focusrite’s optional ADC extend far
significantly improve the quality of
beyond the obvious financial
the sound.
advantages and space saving issues. As
most converters use the same chips, it
is the quality of the surrounding
analogue circuitry that makes the
difference. This is the reason why the
ISA ADC is unrivalled in terms of both
price and performance.
With the converters housed within the
analogue units, the signal path is kept
as short as possible, having no
unnecessary analogue connections to
the inputs of recording equipment. In
“It ıs always easy to jump to the
conclusion that onboard ADC cards
offered on analogue outboard are cut
price in features and performance,
but this simply isn’t the case here. Not
only can I not imagine a digital
scenario that this unit would not
easily interface to, but the quality of
the conversion is extremely good, and
at least the equal of any unit out
there that retails for the same money
for just a converter alone.”
Jon Thornton, ISA 428 review,
Resolution, September 2003
addition, Focusrite units do not contain
extraneous clocks or other sources of
Focusrite’s R and D team have carefully
digital noise, unlike so many
considered the organisation of the PCB
digital desks and multi-I/O
layout and grounding, ensuring that the
DSP configurations.
S/N ratio and linearity of the converter
are optimised. The noise floor and THD
(Total Harmonic Distortion) are kept to a
minimum by the nature of the power
supply and the analogue
input design, with
analogue filtering
positively effecting
the sound of the
digital noise.
In addition, the
supporting circuitry
around the ADC (dealing with data
transmission, bit reduction and
incoming word clock) has been
carefully structured, as it influences the
converter through heat, power supply
and data jitter.
ISA 428: Pre Pack
Think of the ISA 428 “Pre Pack” as a new ‘Old Master’; a unique blend of classic
vintage analogue mic pre’s with state-of-the-art 192kHz digital technology means that
it’s now possible to record using the best of past, present and future audio designs.
Four classic designed transformer-based pre amps.
Eight line inputs
8 Channels of optional cutting-edge 192kHz A/D conversion
4 Front Panel Instrument Inputs – no separate DI box required.
Custom global ADC soft limiter
Switchable Impedance for
unparalleled mic matching or extended microphone creativity (includes ‘Vintage ISA110’ setting for the original Focusrite settings.)
Analogue insert points on every channel.
Focusrite vintage variable High Pass Filters on every channel
New moving coil peak
meters and full 8 channel metering
Four classic transformer-based mic pre amps
with switchable impedance and direct
instrument inputs form the heart of this unit.
These, alongside a custom ‘Soft Clip Limiter’
circuit and an optional eight channel 192kHz
ADC, provide the perfect path into any Digital
Audio Workstation.
The ISA428 also functions as the perfect input
expander for mixing consoles, featuring the
four microphone pre amps, four instrument
inputs, and 8 line inputs. Any combination of
8 of these inputs can be routed discretely to
the 8-channel ADC option.The ISA428 is also
ideal for more traditional stand-alone pre amp
roles in broadcast, post-production, live sound
and installations.
The original design transformer-based pre amps
featured in the ISA428 Pre Pack are the very
same originals to be found in the Focusrite
consoles and classic early ISA110’s.The benefits
of this classic pre-amp topology include superb
common-mode rejection, an excellent overload
margin, and, courtesy of the shared gain
structure, (20dB from the hand-wound
transformer and up to 40dB from the
amplifier,) an extremely low noise floor and
super-wide bandwidth.This pre-amp design is
the cornerstone of Focusrite’s signature ‘warmyet-transparent’ sound and is a standard point
of reference for many of the industry’s most
discerning audio professionals.
The input stage now also provides enhanced
control and creativity, by allowing the user to
switch between four carefully selected input
impedance settings.The original ISA110 setting
is supplemented by three further impedance
settings, to either perfectly match the pre-amp
with any microphone, (and so maximise level,)
or to use different settings creatively to
interactively shape the sound of your chosen
classic mic.
Switchable insert points are also featured on
every channel, allowing routing (between pre
amp and output) to additional external
processing if desired.
Focusrite’s new Soft Limiter is a custom optical
design, which both protects the ADC by
preventing ‘digital overload’, and also eliminates
the unpleasant distortion that standard limiter
circuits often generate.* *
Full output metering for all 8 channels is
provided as standard by 6-segment LEDs on
the ISA428’s front fascia, whilst input levels can
be tracked using the new ‘moving coil’ peak
meters, designed to catch even the fastest and
most elusive of transients.
A brand new optional 8 channel, 24 bit 192kHz
ADC embodies cutting-edge conversion
technology, encompassed within pristine
Focusrite circuitry, providing eight channels of
the highest quality conversion at frequency
rates of up to 192kHz. (Running at 96kHz
provides 16 simultaneous digital outputs
alongside the four main analogue outputs.)
Digital output formats include 8 channel
single/dual wire AES/EBU, 8 channel SPDIF and
single/dual port 8-channel ADAT lightpipe, all
available on a single ADC card.
Two ISA428’s can be used with a single ADC,
utilising the four extra line input channels on
the rear of the unit containing the optional
ADC.This allows expansion from a 4-pre amp
system to an 8-pre amp system – hence why
we named the product “Four t(w)o Eight!”
Revering the past, embracing the future;
combining classic pre amp technology,
innovative custom Focusrite input – and limiter
– circuits, and the very best in A/D conversion
technology, the ISA 428 Pre Pack raises the bar
for multi-channel recording solutions.
“As a stand alone mic pre amp, this unit is
very capable indeed, but with the optional
converter card installed it makes a very
competent and cost effective eight-channel
(four mic, four line) front end for a DAW
or digital recorder.”
Hugh Robjohns, Sound On Sound, May 2003
I S A 4 2 8 S P E C I F I C AT I O N S
= +/- 18dB
= 0 to 60dB (both in 6dB steps)
= +10 to +40 dB variable
= 10KΩ
= Variable - 600Ω,2K4Ω,6K8Ω
and original ISA110 settings
= >1MΩ
= -96dB
= -128dB (EIN with 150Ω input
resistance at 60dB of gain)
= 0.003% with 0dBu, 1kHz input
and 20Hz to 22kHz band pass filter
= 0.003%
Analogue Input and Output connectors (balanced)
Inst inputs
1/4 inch Jack
Mic inputs
XLR (balanced)
TRS Jack (balanced)
Insert Sends and Returns TRS Jack (balanced)
Additional ADC inputs
XLR (balanced)
Analogue Outputs
4 x XLR (balanced)
Dual 9 pin D-types –
8 channel
ADAT Lightpipe (max .96kHz) Optical – 8channel
Bit depths
16, 20 or 24 bit
Frequency options
44.1, 48, 88.2, 96,
176.4 & 192kHz
Clock options
Standard or ‘256 x’
120dB A weighted
192 kHz A/D conversion and the Soft Limiter.
Focusrite’s new ADC convertor is the
company’s first 192kHz design, (it’s also
amongst the world’s first multi-channel 192kHz
audio input devices.) As ever, Focusrite’s
bespoke A/D designs have been crafted in
order to maximise the specifications achievable
with any given converter chip-set. The ISA428’s
ADC offers extremely low distortion, (compare
our figures with any of the A/D ‘heavyweight’
brand names in the market…) and ultra-high
signal/noise ratio specifications (better than
120dB “A-weighted”, comparable with
e.g. Digidesign’s Pro Tools HD™.)
All the advantages of integral A/D conversion
within the main analogue unit’s chassis apply;
the shortest possible record path is achieved,
all unnecessary external analogue connections
are dispensed with, and a quiet and controlled
operating environment for the conversion
process is ensured. There are no extraneous
clocks or sources of digital noise, (as are all too
often found in multi I/O DSP environments,
digital mixers etc) so there is no loss of
accuracy nor clarity. The result is simply
detailed, crystal clear, beautiful
audio conversion.
Focusrite’s revolutionary custom Soft Limiter
provides worry-free, musical A/D conversion,
handling even the hottest analogue signals
with style and grace. It brings warmth to the
conversion process whilst eliminating the
undesirable artefacts caused by digital clipping.
Rather than simply protecting the A/D in a
brick-wall fashion, the Soft Limiter tailors the
last 6dB dynamic range of the A/D converter
to cater for the last 12dB of analogue
headroom. This ensures the A/D converter
never overloads at any point during the
analogue performance. Unlike conventional
limiters, it provides an absolute limit
without destroying the audio integrity of the
source signal.
8 channel systems
8 channels of A/D conversion are fed from the
outputs of channels 1 to 4 (Mic/Line/Inst
channels) with channels 5 to 8 fed from the 4
additional external line inputs on the rear panel.
This allows a single ISA428 unit to act as an
8-channel digital input expansion unit (mic inputs
+ line inputs) to any DAW. Alternatively,
(see diagram right) two ISA428 units with a
single A/D option can be used to create an
8-channel mic pre to A/D system.
Simply feed the analogue outputs of the second
unit into inputs 5-8 of the ADC-equipped unit.
** The ADC Soft Limiter can only operate with the presence of the optional ADC
ADAT is a registered trademark of Alesis Corp. Pro Tools HD is a registered trademark of Digidesign, a division of Avid Technology Inc.
ISA 220: Session Pack
The ISA 220 Session Pack provides all the audio precision tools required to
infuse your session with Focusrite’s renowned sonic performance. It features
many of the original circuits of the flagship ISA 430 MKII Producer Pack, and
also includes some new facilities of its own. It also features the same digital
output option as the originalISA 430, providing you with a high quality digital
route direct fromthe ISA 220 into your digital recording system.
Classic Focusrite transformer-based Mic pre
New Focusrite EQ featuring elements of the original
ISA 110 EQ circuit
Hi and Lo pass filters
De-esser design based on optical technology for lower
distortion and transparency
Precision VU metering of input level or compressor gain
reduction (switched)
De-esser listen for independent monitoring of isolated
sibilant signals
Proprietary Focusrite discrete Class A VCA Compressor design
for better distortion and noise figures
Frequency-adaptive limiter to prevent critical digital overloads
Order of compressor and EQ modules in the signal path can be
switched from the front panel
The ISA 220’s input stage features a
precise VU meter, switchable to allow the
user to monitor either input level or
compressor gain reduction. Situated above
the VU meter is a 32 LED digital meter for
monitoring both the ‘internal’ input and the
rear panel ‘external’ input (the latter routes
directly to the second channel of the
optional high quality stereo A/D card). A
global bypass switch is located to the right
of the digital meter to allow for instant
A/B comparisons.
Mic, Line and Instrument inputs allow
interfacing to any input device, and are all
transformer-based, the cornerstone of the
focusrite signature sound clear yet warm,
with incredibly low noise figures and a THD
below 0.001% on the mic input! Switching
between these input options is available on
the front fascia with LED’s indicating the
active input.
The Mic Pre is the classic Focusrite
transformer-based design as featured in the
ISA 110 with illuminated switches for
phantom power and phase reverse, all
immediately available on the front fascia.
New Blend feature allows uncompressed dynamics to be merged
with the compressed signal path
Optional Stereo A/D – 24 bit 96 KHz Delta Sigma converter
running at 128KHz over-sampling – Dithers down to 20 or16 bit
Further front panel switchable controls
allow control over the Digital output option
and in/out selection for each of the
processors. An instrument jack is provided
on the front panel for quick ‘plug and
play’ access.
The EQ featured on the ISA 220 is similar
to the ISA 430 MK II and ISA 110, except
that the Shelving EQ features four frequency
selections rather than six or eight. Whether
fattening-up bass, foregrounding or
trimming middle, or adding airy top, this EQ
can handle anything.
Next to the Compressor section (which
utilises the same compressor circuit as the
ISA 430 MK II) the ISA 220 features a
‘Compressor Pre EQ’ switch. This allows the
user to place the Compressor either pre or
post-EQ. A new feature in the compressor
section alongside the auto release is the
Blend control, a unique ISA feature,
allowing smoother compression at more
extreme settings. When switched in,
‘Blend’ allows you to mix the
uncompressed signal with the compressed,
thus retaining the power of the dynamics
from the original source.
The ISA 220 also includes the same
De-esser as the ISA 430 MK II, based on a
low distortion optical technology design,
letting you transparently remove excessive
sibilance from a vocal performance. The
output section of the ISA 220 features the
same frequency adaptive limiter as the ISA
430 MK II, a design which uses three
separate stages of optical-based circuits,
each of which has different limiting
properties to give true distortion-free limiting.
Fast limiters tend to have problems dealing
with complex signals that contain sustained
low and mid frequency information and
thus “chop holes” in the audio when HF
transients trigger the limiting. To overcome
this, the ISA 220’s frequency adaptive
limiter has three frequency bands with
different attack times as follows: LF slow,
MF quick and HF ultra-quick, the latter
designed to catch fast transients. The Limitin LED illuminates when the limiter is
active. An upper threshold is fixed at
+20dBu to prevent overload of the internal
(or an external) A/D converter.
“When you unpack any box with the
Focusrite logo on its side you know you
are in for a treat, and the ISA220 proved
the rule once again.This is a well-thoughtout professional product which will
enhance any recording session or facility.”
Hugh Robjohns SOS review March 2002
I S A 2 2 0 S P E C I F I C AT I O N S
Inst. Hi Z I/P
0.003% with 0dBu
123dB EIN with 150Ω
input resistance at 60dB of
Threshold Range:
-28dB to +12dB
1.5:1 to 10:1
Soft knee
500µS to 25mS
100mS to 4S, variable or
auto (program dependent)
“If youıre looking for an all-in-one input
channel that can also be put to work
Eqing, compressing and de-essing signals
during mixdown, the Session Pack should
top your list.The unit sounds great, is
flexible and covers everything you might
need to get signal in to your recorder,
whether analogue or digital.”
Threshold Range:
Frequency Range:
Ratio at Centre
2K2 to 9K2
Threshold Range:
infinite (Brick Wall)
Frequency dependent
ADAT Lightpipe
Bit depths
Frequency options
Clock options
(Super Clock)
RCA Phono
16, 20 or 24 bit
44.1, 48, 88.2 &
Standard or ‘256 x’
113dB A weighted @
Mitch Gallagher, EQ, June 2003
Finally, a variable control adjusts the
module output level between -60dB and
+6dB ensuring optimum output levels.
The optional A/D card can be purchased
with the unit, or retrofitted at a later date. At
the heart of the A/D card is a high quality
24bit 96KHz Delta Sigma converter running
at 128KHz over-sampling for maximum
conversion performance. Focusrite
proprietary designs are used for all internal
clocking and phase lock loop circuits to
guarantee the absolute minimum jitter
possible, whether free-running or locked
to wordclock.
The ISA 220's
optional A/D is
stereo and allows for inputs from internal
(post-processing) and external sources
simultaneously giving a clean, protected,
high-quality path to stereo digital media.
Thus, with the Stereo A/D card installed, the
ISA 220 can be used as a high quality
mono/stereo tracking converter, or at mix
down as a stereo converter channel for
routing complete mixes to digital media.
Two ISA 220 Session Packs can take full
advantage of the one A/D converter, with one
ISA 220 acting as the master and the other
as the slave.
Red 1: Quad Mic Pre
Using the same circuit topology as the original ISA mic pre designs, the Red
1 and 8 offer respectively, four and two channels of ultra-high quality
Focusrite microphone amplification. Used with high quality ribbon, valve and
condensor mics, the Red 1 and Red 8 obtain outstanding results with any
sound source, but especially voice, piano and string instruments.
Classic Focusrite Mic Pre transformer-based design
VU output level meter
Scribble disc
With four mic pre-amps in a single unit, the
Red 1 is ideal for those looking for
improved audio performance, as a compact
‘way in’ to digital recording systems, or for
location multi-mic recordings. Each
channel offers custom-wound Focusrite
input transformers, switchable phantom
power, phase reverse, an easily-read
illuminated VU meter, and a handy scribble
disc for denoting channels. Mic gain is
switched in 6dB steps over a 66dB range,
for accurate, precise channel matching and
recall. The Red 8, with a perfectly matched
pair of mic amps, offers identical channel
controls to the Red 1, and is especially
suited to demanding mono or stereo
recording work, such as location classical
recording with digital recording media.
The many benefits of the unique Focusrite
mic amp topology include superb commonmode rejection, a good overload margin
and, with its shared gain structure, (20dB
from transformer and up to 40dB from the
amplifier) a very low noise floor with the
signature wide bandwidth (10Hz to
Phase reverse and phantom power
Stepped gain potentiometers
200KHz). It also maintains this level of
performance with a very wide range of
impedance across the inputs. In practice,
this makes it what one reviewer called,
“perhaps the most revealing yet forgiving
mic pre-amp in history.”
The output stages of both the Red 1 and
Red 8, with their custom transformers, will
easily drive very long cable runs – up to
several kilometers – without significant
loss of quality, making them ideal for
remote recordings.
“Performance-wise, Red 1 is excellent,
having a noticeably broad frequency
response with well-defined low end and an
open high end; mid frequencies sound
both open and well-focused.”
Patrick Stapely - Studio Sound
“Versatile yet straightforward operation
means the Red 1 can be relied upon at
all times to produce the required quality
of signal to tape.”
Steve Power - Producer for Robbie Williams
R E D 1 & R E D 8 S P E C I F I C AT I O N S
Mic input gain
-6dB to +60dB in
6dB steps
Mic Input Impedance
1200Ω ±15%, balanced
and floating
Frequency Response
10Hz to 140kHz
(-3dB points), ±0.1dB
within passband
Noise (EIN)
-127dBu (input loaded
200Ω) @ 60dB gain
0.15% (-20dBu @ 20Hz)
0.06% (-20dBu @ 40Hz)
0.003% (-20dBu @ 1kHz)
0.005% (-20dBu @ 10kHz)
+24dBm into 600Ω
+26dBm into 10kΩ,
balanced and floating
Red 8: Dual Mic Pre
The Focusrite Red Range
The Focusrite Red Range is handmade, crafted to the highest
standards. All the Red Processors are
manufactured solely in the UK using
machine-tooled, half-inch thick
claret red anodised aluminium. The
chassis features recessed section
grooves and styling motifs,
(sculpted with diamond-tip cutters,)
porthole windows, anoprinted silver
control text, and firm-response
illuminated switches.
All potentiometers are manufactured
to Focusrite’s own specification by
French company ‘Sfernice’, and are
made from conductive plastic which
gives more sensitivity and no
mechanical resistance (easy to make
very fine adjustments).
All Red products feature sealed relays,
(gold-plated silver in an inert gas,)
situated in the middle of the circuits
in which they switch. The precious
metals mean that all contacts are low
resistance, and the gas prevents any
kind of corrosion of the surface of the
contacts, meaning the most perfect
audio switching device ever designed utterly passive, zero distortion caused
and no FET’s required.
65kHz Resonant Peak
-1dB at 20Hz
-3dB at 150kHz
The Legendary ISA Mic Pre sound is shaped by its unique profile,
with its extended frequency range and 65kHz resonance,
developed by ear rather than at the test bench.
Red Range processors with mic pre’s
feature solid-state-amplified audio
transformers, which help to give the
characteristic “warm, organic sound”
loved by studios world-wide.
Transformers are the only way of
giving a truly floating and earth-free
Classic Focusrite Mic Pre transformer-based design
VU output level meter
Scribble disc
system, because there’s no galvanic
connection between the input and
output circuitry.
Transformers are not new in audio;
they were there at the outset, but
whilst others were trying to design
them out to cut costs, Focusrite went
after the best transformer possible, a
philosophy which resulted in the
transformers you find in the Red
series today.
Low frequency second order distortion
created by transformer saturation
provides the character that many
perceive as ‘warmth’. Meanwhile, a
high frequency emphasis generated by
the reactance of the coil resonance
with the terminating impedance of the
microphone or receiving device,
provides the engineer with open,
spacious high frequencies.
The Red Range mic transformer in
particular gets its legendary
“transparent yet warm” label from this
process, an apparent contradiction in
terms, yet a genuine characteristic –
audition a unit and hear for yourself.
“The Focusrite Red Range is a reviewer’s
dream come true.”
Dave Foister, Studio Sound
Phase reverse and phantom power
Stepped gain potentiometers
Red 2: Dual Equaliser
Focusrite Equalisation has a unique design heritage and is renowned
for the ease with which outstanding, warm, musical results can be
obtained. The Red 2 offers two comprehensive channels of Focusrite
EQ with transformer-balanced line level inputs and outputs
Two channels of classic Focusrite EQ
Discrete High and Low pass filters
In/out switching and x3 switching on mid bands
Switched High and Low shelving bands
These transformer-balanced inputs and
outputs provide superb isolation, and this
classic approach to interfacing contributes
to the warm sonic signature of the
Focusrite EQ. In fact many owners run their
signal paths through the Red 2 to obtain
this warmth whether or not they are
applying the filters or equalisation.
Derived from the classic ISA 110, the Red
2 equaliser offers switched-frequency high
and low-pass filters, switched frequency
shelving bands for low and high
frequencies, and two fully parametric mid
bands with frequency sweep and Q controls.
The shelving high and low bands offer up
to 18dB cut and boost from 3.3–18kHz
and 33–460Hz respectively, with a
constant filter curve shape – unaltered by
frequency selection – for smooth,
predictable results.
The two fully-parametric, mid bands have
considerable overlap in available frequency
selection. The low-mid band is sweepable
from 40-400Hz or (x3) 120Hz–1.2kHz. The
high mid band is sweepable from
Total isolation between bands
600Hz-6kHz or (x3) 1.8kHz-18kHz. The
bandwidth (or Q) is continuously variable
from 0.3 to 1, allowing a broad or very fine
“peaking” or “dipping” curve to be obtained
with up to 18db of gain or attenuation.
The high and low-pass filters provide
12db per octave attenuation and are
switchable in steps between 36Hz –
330Hz and 5.6kHz–22kHz respectively.
They are indispensible for cleaning up
signals corrupted by noise at either end
of the spectrum.
“You need sweet sounding EQ which the
Red 2 has. I use it frequently to brighten
or refine vocal sounds in the mix.”
Steve Power – Producer for Robbie Williams
and other artists
“…offers exemplary quality. Red 2 gave
excellent, fast results on a wide range of
programme material, with minimum fuss.
Whether fattening-up bass, hardening or
softening middle, or adding airy top, it was
quick and intuitive to use.”
Patrick Stapely, Studio Sound
High and Low fully parametric mid bands
R E D 2 S P E C I F I C AT I O N S
Input Gain
-12dBu to +12dBu,
continuously variable
Input impedance
10kΩ ±15%, 20Hz to 20kHz
Frequency response
5Hz to 200kHz (-3dB points)
±0.1dB within passband
Better than -98dB
below +4dBu
0.016% (-20dBu @20Hz)
0.02% (-10dBu @20Hz)
0.03% (0dBu @20Hz)
0.0025% (0dBu @10kHz)
+26dBm with 600Ω output
load, balanced and floating
Why is Focusrite EQ so special?
The Focusrite design for the original
ISA110 EQ was commissioned as a
custom rack for Air Montserrat, and
later at George Martin’s personal
request, for the custom Neve at Air
London, (these units are still working
at Air Lyndhurst today.) But what
makes the Focusrite EQ so special?
Musical EQ
Infinite Control
The design, like most great designs, is
relatively simple; a classic six band
EQ, with shelving high and low
bands, parametric low mid and high
mid bands, and low and high pass
filters. The HF and LF shelving EQ’s
are unique – they are an
implementation of the legendary
Baxandall circuit designed in the
1950’s. The EQ is inherently
expensive to build as a circuit; most
typical shelving filters are variable
resistance, fixed capacitance, but the
design featured instead variable
resistance for gain and variable
capacitance for frequency. The
positive benefit of this high-end
design is that there is no interrelation
between EQ bands, (making a change
to one band has zero effect on
another band,) and that the EQ is
virtually noiseless.
implementation of the state variable
circuit configuration – separate
amplifiers for the Q, and for lowmid/high-mid gain. The usual cheap
way to simulate this is to implement a
compromise – a gyrator mid-band
peaking circuit – but cutting corners
in this way invariably means a poor
imitation of the real thing. The
Focusrite way has, from the
beginning, been to choose the
solution that sounded best then
minimise cost through elegant design.
This has carried right through from
the 1st ISA 110 modules to the
current Focusrite core technologies;
EQ, Mic pre amps and Compression.
“Throughout its history, the basic
philosophy of Focusrite has remained
constant... to provide uniquely styled
audio products, engineered using the
highest quality circuits – a philosophy we
have held true to this day.”
Phil Dudderidge, Chairman,
Focusrite Audio Engineering
The HF and LF EQ features switched
capacitor circuits, rather than a
variable resistor circuit. (The shape of
the shelving filter in the case of a
variable resistor circuit varies
according to the frequency, thus
shelving response is not pure, it’s
shallow at one point, steep at
another.) With the ISA 110, this
switched capacitor circuit means the
Q is constant, and the EQ slope is
constant, meaning accurate,
predictable, beautiful results.
The high-mid and low-mid EQ bands
are fully parametric, and are a full
Red 3: Dual Compressor / Limiter
The Red 3 employs an unusual and original single-VCA design to
achieve high quality and truly independent compression and limiting,
without the compromise and unnecessary processing involved in
traditional designs. The success of the design is attested to by the
Red 3’s TEC award for Outstanding Technical Achievement in the
Signal Processing Technology category
Stereo switch for true stereo operation from a single set of controls
Key inputs with illuminated push-button selection
Illuminated push-button switches for compressor/limiter in/out on each channel
Precision VU metering of signal level or gain change (switched
Can operate as a discrete channel unit
The VCA used is a proprietary Focusrite
Each channel has clear and identical
design, fully discrete and balanced, offering
controls, for compressor ratio, threshold,
superb low noise and distortion, and
make-up gain, attack and release, and
excellent common-mode rejection. In order
R E D 3 S P E C I F I C AT I O N S
Input sensitivity
limiter threshold. A program-dependent
Input Impedance
10kΩ ±15% (20Hz to 20kHz)
to separate compression and limiting, the
auto-release mode is available, and the VU
side-chain electronics contain three VCAs
meters can be switched to show levels in
Frequency response 5Hz to 200kHz (-3dB points)
in series to generate compression and
two ranges, or gain change. In stereo mode
limiting control voltages which drive the
the lower set takes control of both channels.
Better than -80dB below
+4dBu output level
0.02% with input at 0dBu
at 1kHz
0.006% (+10dBu @ 1kHz)
0.004% (+20dBu @ 1kHz)
+24dBm with output loaded
600Ω, balanced and floating
main VCA. The result is true compression
followed by limiting, rather than the more
common characteristic of compression that
turns into limiting. The side-chain
electronics are class A, ensuring superb
transient response. Both compression and
limiting therefore, offer true peak response,
not averaging RMS response.
The use of such a high quality audio VCA
as the only element between input and
output means a very short signal path, and
an ability to retain a natural, unobtrusive
“…possibly the cleanest, quietest,
most unobtrusive compressor I have
ever used…”
Dave Foister, Studio Sound.
“...the Focusrite Red 3. I always put
finished, stereo mixes through the
Focusrite. It pulls the mix together a bit. I
call that ‘kissing the Focusrite’”.
sound even when significant compression
Tom Lord-Alge; Recording/Mixing Engineer –
is being applied.
derived from an interview in Sound on Sound.
Every mic-pre and compressor
in history; nailed.
The Liquid Channel is a revolutionary professional channel strip that precisely replicates any classic mic-pre
and compressor. Combining radical new analogue pre-amp technology with dynamic convolution techniques.
The Liquid Channel fuses cutting-edge analogue design with lightening fast SHARC DSP. Augmented by fully
digital controls and optional remote software, The Liquid Channel provides the ultimate fluid vintage collection.
Loaded with 40 classic mic-pre’s and 40 classic compressors
99 User memories save every parameter
Endlessly expandable library of replicas via USB download
Software application allows comprehensive control
192kHz internal processing and ADC/DAC as standard
New Focusrite digital EQ
Adjustable 2nd order distortion accounts for variance in vintage originals
Ask for The Liquid Channel’s dedicated brochure, or for the latest reviews and
up-to-date product details, check out
Disclaimer: The impulse responses in The Liquid Channel are the true impulse responses of the original equipment replicated. All manufacturer, product and trade names referred to or implied in
this document are the properties of their respective owners. Focusrite neither expresses nor implies any functional similarity to products developed and marketed by other manufacturers, nor
does Focusrite express or imply any endorsement by these other manufacturers of Focusrite or vice versa.
Red 7: Mic Pre & Dynamics
Combining the Focusrite transformer-based mic pre with a
compressor, limiter and de-esser/exciter, the Red 7 is a superb,
single-channel dynamics processor, ideal for high quality recording,
notably voice-overs and other vocal applications
Line input balance control
Scribble disk
Classic Focusrite mic pre, compressor, de-esser and exciter designs
Illuminated push-button switches for compressor in/out, de-esser/exciter in/out and high pass filter in/out
Precision VU metering of signal level or gain change (switched)
The Red 7 employs the same superb mic
pre-amp as the Red 1 and Red 8, with a
dual-range mic gain pot that allows precise
control across the full range of the device.
Phantom power and phase reverse are also
provided. The Line input is electronically
balanced, with continuously variable gain.
A high quality output fader offers +6dB
gain to infinite attenuation, essential for
direct recordings, or for accurate level
matching after EQ and dynamics.
unit, is characterised by low noise and
distortion even with heavy processing.
Relatively heavy compression can be
applied whilst retaining a transparent
natural sound. Ratio, gain make-up,
threshold, attack and release are all
continuously variable, and a program
dependent auto-release mode can be
switched in. A swept high-pass filter allows
effective treatment of problems such as
rumble, bass lift and proximity effect.
Added to this mic pre is a full dynamics
section, optimised for vocals. With its
superb signal path, outstanding ease of
use, and an integrated all-in-one design, it is
a powerful tool for voice recording in all
situations from music studios to postproduction. The compressor design is taken
straight from the Red 3, and as on that
The de-esser/exciter stage can be switched
to provide frequency-selective compression
(de-essing) or excitation. The amount and
centre frequency of the processor are
continuously variable, and as all the unit’s
dynamics still use the Focusrite single-VCA
“The Sound dept of PINEWOOD
STUDIOS Ltd has been using the Focusrite
Red 7 for many years; we have 7 in total.
The two main areas of use are the Mic
pre-amp and de-esser. For these purposes
they do the job extremely well and we
have found them to be very reliable.”
Martin Powlesland. Technical Manager
Pinewood Studios Ltd
technique, unwanted colouration of the
sound is kept to an absolute minimum.
A clear VU meter shows level after the
pre-amp gain control, or displays
compressor gain change.
R E D 7 S P E C I F I C AT I O N S
Mic Input Gain
-6dB to +60dB in two
variable ranges
Mic Input Impedance 1200Ω ±15%, balanced
and floating
Line Input Gain
-12dB to +12dB
Line Input Impedance 10kΩ ±15%,
electronically balanced
Input balance
>60dB to 15kHz on both inputs
Frequency Response 10Hz to 140kHz (-3dB points),
±0.1dB within passband
Better than -80dB below +4dBu
output level, dynamics in
0.006% (+10dBu @ 1kHz)
+24dBm into 600Ω
+26dBm into 10kΩ,
balanced and floating
EQ Magazine Blue Ribbon
Award 2002
ISA 220 Session Pack
Computer Music
Ultimate Buy Award
Platinum TrakMaster
Future Music
Best Buy Award
Platinum Penta
Mix Foundation
TEC Award Nomination 2001
ISA 430 Producer Pack
Mix Foundation
TEC Award Nomination 2001
Platinum MixMaster
Mix Foundation
TEC Award 1995
Red 3 Compressor
Future Music
Platinum Award
Platinum Penta
Mix Foundation
TEC Award 1996
Red 7 Mic Pre/Dynamics
Future Music
Platinum Award
Platinum TrakMaster
Future Music
Best Outboard 2002
Platinum Penta
Mix Foundation
TEC Award 1997
Green 1 Dual Mic Pre
Electronic Musician
Editor’s Choice 1998
Voice Processor
Green 3 Voicebox
Dutch Future Music Magazine
Platinum Award 1998
Platinum Tone Factory
Studio Sound
SSAIRA Award 1999
Best Combined Outboard Device
Platinum VoiceMaster
Mix Foundation
TEC Award Nomination 1999
Platinum VoiceMaster
Electronic Musician
Editor’s Choice 2000
Voice Processor/Channel StripPlatinum VoiceMaster
Studio Sound
Winner - Best EQ
ISA 430 Producer Pack
Best Pre-amplifier 2002 Award
RED 8 Dual Mic Pre
Future Music
Best Outboard 2002
Platinum VoiceMaster PRO
Pro Audio Review
PAR Excellence Award 2002
Platinum VoiceMaster PRO
Mix Foundation
TEC Award Nomination 2003
ISA 428 Pre Pack
Studio Sound
Nominee for
Best Combined Outboard
ISA 430 Producer Pack
[ Focusrite Awards & Nominations ]
Available From:
Focusrite Audio Engineering Ltd. Phone:+44 (0)1494 462246
Fax:+44 (0)1494 459920 email:
Distributed in North America by Digidesign. Phone (650) 731-6300
Fax (650) 731-6399 or toll free on 866 FOCUSRITE
Download free samples, Flash demos, user guides, screensavers,
further information and more at;
™ ISA 430 MK II, ISA 428 Pre Pack, ISA 220 Session Pack, The Liquid Channel, RED 1,2,3,7 and 8 are Trademarks of
Focusrite Audio Engineering Ltd.
E and OE
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