ISA 430 Manual (multilanguage)

20/1/2000

9:08 am

Page 55

ISA430 users manual

Focusrite

audio engineering

9:06 am

Page 1

Introduction

Important Safety Instructions
Read all of these instructions and save them for future reference. Follow all warnings and instructions marked on the unit.
hank you for purchasing the ISA430 brought to you by the Focusrite team Trevor, Peter, Martin, Helen, Tom, Mick, Phil, Chris, Micky, Pauline, Jo, Chris, Nathan, Rob, Peter and Simon. The chaps at Focusrite are a jolly hard working bunch and take a great deal of pride in designing, building and delivering products which are considered the best audio units around; we hope your new Focusrite unit lives up to that reputation and that you enjoy many years of productive recording. If you would like to tell us about your recording experiences then email us at: sales@focusrite.com
Do not obstruct air vents in the rear panel. Do not insert objects through any apertures. Do not use a damaged or frayed power cord. Unplug the unit before cleaning. Clean with a damp cloth only. Do not spill liquid on the unit. Unplug the unit and refer servicing to qualified service personnel under the following conditions: If the power cord or plug is damaged; if liquid has entered the unit; if the unit has been dropped or the case damaged; if the unit does not operate normally or exhibits a distinct change in performance. Adjust only those controls that are covered by the operating instructions.

E N G L I S H

The Focusrite Team
Do not defeat the safety purpose of the polarised or groundingtype plug. A polarised plug has two blades with one wider than the other. A grounding type plug has two blades and a third grounding prong. The wider blade or the third prong are provided for your safety. When the plug provided does not fit into your outlet, consult an electrician for replacement of the obsolete outlet.

Contents

WARNING:
Important Safety Instructions.1 Power Connections.1 Signal Connections.2 Getting to Know the ISA430.3 Metering.3 Input Stage.3 EQ Module.4 Compressor.5 Gate.6 De-Esser.6 Limiter.7 Output.7 Stereo A/D.7 Single/Split Mode.7 Output Modes.8 Applications.9 Specifications.51 Warranty.51 Focusrite Distributors.52 This unit is capable of operating over a range of mains voltages as marked on the rear panel. Ensure correct mains voltage setting and correct fuse before connecting mains supply. Do not change mains voltage settings while mains supply is connected. To avoid the risk of fire, replace the mains fuse only with the correct value fuse, as marked on the rear panel. The internal power supply unit contains no user serviceable parts. Refer all servicing to a qualified service engineer, through the appropriate Focusrite dealer.
THIS UNIT MUST BE EARTHED BY THE POWER CORD
UNDER NO CIRCUMSTANCES SHOULD THE MAINS EARTH BE DISCONNECTED FROM THE MAINS LEAD.

Power Connections

There is an IEC mains lead supplied with the unit which should have the correct moulded plug for your country. The wiring colour code used is: For units shipped to the USA, Canada, Taiwan and Japan: Live - Black Neutral - White Earth - Green For units shipped to any other country: Live - Brown Neutral - Blue Earth - Green and Yellow

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Signal Connections

Optional A/D Card shown

XLR (Audio) Inputs and Outputs
All 3-pin XLR audio connectors (Outputs, Mic/Line Inputs, Insert Send & Return) are wired as follows: Pin 1 Pin 2 Pin 3 Screen/Chassis Audio 0 Audio 180

INT A/D Direct

The Internal A/D Direct input is used to route an external signal directly to the A/D card via the Limiter. It replaces the Internal signal feed to the A/D card (i.e. whatever is connected to the mic, line or instrument input.)

EXT IP A/D Direct

The External A/D Direct input is used to route an external signal to the optional A/D card via the Limiter. The signal is normally fed to the spare side of the A/D card not being used by the internal signal, and so does not replace it. However it is possible to also sum the External A/D Direct input together with the main internal signal, (i.e. whatever is connected to the mic, line or instrument input,) using the sum button on the front panel. This will result in whatever is connected to the External A/D Direct input being routed to both sides of the A/D converter. For example, a reverb signal could be processed externally and then be summed with a dry snare drum signal in this way.
Instrument Input, Key IPS, Int A/D Direct and Dynamic Link
1/4 Jack wired as follows: Tip Ring Sleeve Audio 0 Audio 180 Screen/Chassis
Mic IP/Line IP/Inst. Hi Z IP
Any one of these inputs may be used as the main input to the ISA430. Signals routed to these inputs are referred to as the internal or Int signal path.

Insert Return

This is used as the insert input point, or as the input to the dynamics modules in split mode (see Dynamics Split diagram on page 7.)
This output is used as the main analogue internal signal output, and is fed by whatever is connected to the mic IP, Line IP or Inst. Hi Z IP, aftyer this signal has been routed through the EQ and dynamics modules (in singlemode) or through EQ only (in split mode.)

Insert Send

This is used as the insert output point, or as the analogue output from the dynamics module in split mode (see Dynamics Split diagram on page 7.)

Dynamic Link

You can connect two ISA430 units (using a standard stereo jack to jack lead between the DYNAMIC LINK sockets) to allow the dynamics sections to behave as a stereo pair of processors. When connected in this way the dynamics processors behave as if both units were receiving the same level of signal, with both units responding to the higher level of the two signal paths. The EQ channels can be matched visually or aurally to be used as a stereo pair if required.

Post Mic OP

This is used as an output from the point immediately after the mic pre (i.e. before EQ and dynamics modules.) It is used as a direct-to-tape ultra-short signal path output. Taking a signal from this post mic OP does NOT interrupt the signal flow from the mic pre to the EQ, dynamics etc., so a direct feed to tape can be achieved, whilst simultaneously allowing processing of the same source.
Retrofitting the Optional A/D Card
The optional A/D card can be retrofitted to a standard ISA430 at any time. Full fitting instructions for this option are included with the Card.

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E N G L I S H Getting to Know the ISA430 Power
Applies power to the unit. Turn on the ISA430 before powering up devices to which the outputs are connected.

Listen LED

This illuminates when LISTEN is selected on the Compressor, Expander/Gate or De-Esser and indicates that the unit is monitoring the selected side chain frequencies. Note that the VU meter continues to show the signal chosen by VU SELECT and not the LISTEN signal. What you are watching and what you are hearing can be two different things!

Bypass

The EQ and Dynamics processing modules can be globally switched out using the BYPASS switch, providing a direct route (except for the protection of the multi-band limiter which remains in the circuit) from Line Input or External Input to the A/D inputs. This enables the unit to be used as a 24 bit, 96k stereo converter for final mastering or for analogue transfer to digital.

O/L LED

This LED illuminates when the peak signal level reaches or exceeds +20dB, or when the peak signal level reaches 6dB below clipping. The signal is monitored at four points: after the input gain TRIM, after the EQ module, after the Dynamics module and after the Insert Return, since each module could cause clipping if incorrectly set up. Occasional short-duration peaks which may cause the LED to blink will not normally cause audible distortion, but if the LED is lit constantly, the level in the appropriate module should be reduced to prevent overloading.

Inst I/P

Instrument sources may either be connected via the rear panel, or via this front panel jack.
Input Stage Metering VU Select
The VU Meter can display input level, insert return level, or the compressor gain reduction. Press VU SELECT to step through the three sources as indicated by the corresponding LEDs. For the Input and Insert Return, 0VU corresponds to +4dBu. For the Compressor the meter indicates the amount of gain reduction caused by compression, from 0VU (no compression) to -20VU (corresponding to 20dB of gain reduction). Three input options are provided to give compatibility with Mic, Line or Instrument sources. An immediately-post-mic pre balanced output (Post Mic OP)is provided on the rear panel giving an ultra-short signal path to allow for the cleanest possible recordings.

Select

Pressing SELECT steps through each of the three inputs as indicated by the corresponding LEDs. When the Mic LED is lit, the Mic input is active etc. Only one of the Mic, Line or Inst inputs can be used simultaneously.

Digital Output Meters

Two LED bargraph meters monitor the Internal signal and the External signal (whatever is connected to the Ext I/P A/D Direct XLR input) at a point after the Limiter but before the A/D input. The meters provide a wide range with the O/L LED (lower right side) acting as an Overload indicator to warn of excessively high levels at the input of the A/D converters.
Mic input sensitivity is switched from -60dB to +6dB in 6dB steps. Phantom power is available on the rear panel XLR for condenser mics when +48V front panel switch is pressed.
A Line input is available on XLR, with a switched gain control giving a range of +/-18dB in 6dB steps. 3

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An Instrument input is available on 1/4 jacks on either rear panel or front panel. This is suitable for high impedance sources such as guitars or bass pickups (which may be connected directly without the need for a DI box), or synthesisers with low level outputs.

Low Pass Filter

A variable control sets a rolloff frequency from 400Hz to 22kHz.

High Pass Filter

A variable control sets a rolloff frequency from 20Hz to 1k6Hz.
The TRIM control provides additional variable gain of 0 to +20dB for MIC and LINE inputs (white legend), or 0 to +40dB for the Instrument input (yellow legend).
When the COMP switch is pressed both filters are inserted in the Compressor sidechain for frequency-selective compression. This selection is cancelled if FILTER IN or GATE is pressed.
Provides +48V powering for condenser mics when pressed.
When the GATE switch is pressed both filters are inserted in the Gate sidechain to assist accurate drum gating. This selection is cancelled if FILTER IN or COMP is pressed.
Pressing PHASE reverses the phase of the selected input, to correct phase problems with close microphones or incorrect wiring polarity.

EQ Module All EQ

Pressing ALL EQ activates all sections of the EQ module (including the Hi and Lo Pass Filters), placing the whole module in the audio path. Toggling ALL EQ allows A/B comparison of EQ settings without having to use BYPASS which switches both EQ and Dynamics modules in or out of the audio path. The COMP and GATE switches on individual EQ sections (see below) operate independently from the ALL EQ switch.

PARAMETRIC EQ

Two separate bands of parametric EQ are provided, each with continuously variable boost/cut with centre detent, sweep control with two ranges, and variable Q. The first band covers the range 40Hz to 400Hz (120Hz to 1k2Hz when x3 is pressed) and the second band covers 600Hz to 6kHz (1.8kHz to 18kHz when x3 is pressed).

Param EQ In

Press in to switch the Parametric EQ into the signal path. This selection is cancelled if GATE or COMP is pressed.

Filter In

Press in to make the Hi and Lo Pass Filters active in the audio path. This selection is cancelled if COMP or GATE is pressed. Both filters provide 18dB/octave rolloff, and since the filter frequencies overlap they may be configured as a very tight bandpass filter for creative compression and gating; use when you wish to select a specific instrument or narrow frequency band from a complex signal, then feed to the sidechain of the compressor or gate. 4
The Sweep controls have two ranges, the higher being selected when the x3 switch is pressed (frequencies shown in yellow on the panel).
When the COMP switch is pressed, the Parametric EQ is inserted in the Compressor sidechain allowing frequency-selective compression. This selection is cancelled if PARAM EQ IN or GATE is pressed.

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When the GATE switch is pressed the Parametric EQ is inserted in the Gate sidechain for accurate drum gating. This selection is cancelled if PARAM EQ IN or COMP is pressed.

Comp Listen

Press to allow audio monitoring of the compressor sidechain to assist accurate frequency adjustment during setup. The LISTEN LED beside the VU meter illuminates to show that Listen mode is active.

SHELVING EQ

High and Low frequency shelving sections are available, each with continuously variable boost/cut with centre detent, and a six position rotary switch for selection of rolloff frequency.

Attack

ATTACK determines how quickly compression is applied once the level of the source signal has risen above the Threshold. When turned anticlockwise the response is very fast, which tends to make the compressor react to the peak levels of the signal. This is sometimes desirable, but can cause unwanted pumping of steadier low level components of the signal by short transients. A slower attack will cause the compressor to ignore short transients and respond more to the average loudness of the signal; however this may seem to increase relative volume of the transients.

Shelving EQ In

Press in to switch all the Shelving EQ into the signal path. This selection is cancelled if GATE or COMP is pressed.
When the COMP switch is pressed the Shelving EQ is inserted in the Compressor sidechain for frequency-selective compression. This selection is cancelled if SHELVING EQ IN or GATE is pressed.

Release

RELEASE determines how quickly compression is removed once the level of the source signal has fallen below the Threshold. When in the anticlockwise position, the compression releases very quickly, which may be appropriate on rapidly varying signals to avoid compressing the beats that follow, but can result in excessive distortion on more sustained material. Clockwise rotation increases the release time, giving a smoother effect, but which at the same time may result in transients causing audible pumping. Rotation fully clockwise switches release to AUTO, substituting an adaptive attack/release circuit which essentially varies the release rate to suit the dynamics of the signal. This enables the use of fast attack times without any pumping type artefacts, especially effective on complex programme material. The release rate is probably the most important variable when recording rock music, since it controls loudness. Loudness is determined by the maintenance of high mean levels: compression increases the proportion of highlevel signal content, and as the diagram shows, the faster the unit releases, the more low-level signal is brought to a higher level. Therefore, the faster the release rate, the higher the perceived loudness of the recording.
When the GATE switch is pressed the Parametric EQ is inserted in the Gate sidechain for accurate drum gating. This selection is cancelled if SHELVING EQ IN or COMP is pressed.

Compressor Comp In

Press COMP IN to switch the compressor into the signal path. Note that the VU meter can be selected to display the compressor gain reduction (see Metering section).
The RATIO control determines the rate at which compression is applied to the signal with increasing input, and is the ratio of change in input level compared to change in output level. The control gives a range of 1.5 to 10. Higher Ratio settings will produce more noticeable compression, so for the least obtrusive result, the Ratio should be set at the minimum necessary for the application. For example, using low Threshold and low Ratio will produce less subjectively noticeable effect than a high threshold and high ratio, even though the total amount of compression may be the same.

Threshold

THRESHOLD determines the level at which compression begins, with a range -28dB to +12dB. The lower the Threshold, the more the signal is compressed. Setting a higher Threshold allows quieter passages in the music or speech to remain unaffected; only passages that exceed the Threshold will be compressed. 5

De-Esser

The DE-ESSER is based on an optical technology design, letting you remove excessive sibilance from a vocal performance (if ess sounds are over-emphasised).

De-Ess In

Press in to activate the De-Esser.
Threshold determines the level at which the gate opens, (or at which gain reduction finishes when in Expander mode.) The higher the threshold, the more the low-level noise is reduced, and the more extreme the effect.
THRESHOLD determines how much de-essing is being applied to the selected frequency. The lower the threshold (control anticlockwise), the more de-essing is applied.
HOLD controls the variable delay before the gate release starts. This allows the Gate to be held open until the signal has decayed away sufficiently that the quite rapid onset of gain reduction isnt noticeable: alternatively the signal can be deliberately truncated before its natural end for special effects. 6
This control selects a frequency to remove between 2k2Hz and 9k2Hz.

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De-Ess Listen
Press to allow monitoring of only the signals which will trigger activation of the De-Esser rather than hearing the overall effect in a complex signal. The LISTEN LED beside the meter illuminates to show that Listen mode is active.

Ext Sync

Press to select the EXT SYNC input on the rear panel. This allows theISA430 to be slaved to external wordclock.
Single/Split Mode Selection
The unit can be run as a single channel Producer Pack, or split to act as two independent processors running discrete audio paths. Split mode allows the INSERT SEND and INSERT RETURN connections to act as independent inputs and outputs to the dynamics section only, creating two devices in one, with separate EQ and Dynamics; perfect for mix down.

Active LED

This LED illuminates when the De-Esser is active at the chosen frequency, and shines brighter with increasing level reduction.

Setting up the De-Esser

Press DE-ESS LISTEN with THRESHOLD at maximum and slowly reduce until the selected frequency begins to trigger the De-Esser. Vary the frequency control to find the exact area of the signal which you wish to remove. Once located, switch off DE-ESS LISTEN and adjust THRESHOLD for the amount of reduction required. No further adjustment of FREQUENCY should be required, as the hot spot will have been more precisely found using DE-ESS LISTEN.

Dynamics Pre Eq

Normally the EQ section is first in the signal path. Pressing PRE EQ reverses the position of the EQ and Dynamics sections, placing Dynamics first and EQ afterwards.

Split Dynamics

Press SPLIT DYNAMICS to separate the EQ and Dynamics sections, creating two independent modules as shown below.

LIMITER Limit In

Press to activate the multi-band limiter. Three separate fixed frequency bands with different limiting properties give true distortion-free limiting.

This 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.

Output Sum

Press to route both the internal signal and external line input signal (from the EXT I/P A/D DIRECT rear panel jack) to the module output. (External signals could be a double track, an extra mic from a second ISA430 or live reverb.)

Insert In

Normally the insert is bypassed. Pressing INS IN places the insert in the audio path in the selected position.

External

This control adjusts the gain of the external line input, which may be summed into the module output (see above).

Insert Position

The Insert Send and Return may be positioned in three places within the unit for maximum versatility, as shown in the diagram. Pressing the INSERT POSITION switch steps through the three options, as indicated on the corresponding LEDs. The options are PRE (Insert is after the input Trim, but before EQ or Dynamics, (depending on the setting of the DYNAMICS PRE EQ switch)), MID (between EQ and Dynamics) or POST (after EQ and Dynamics and before the main output).

Output

A variable control adjusts the module output level (OP1) between -60dB and +6dB.
Press to mute the output from the unit.

Stereo A/D

The ISA430 can be used as a high quality stereo converter channel for final mastering, or for analogue transfer to digital (by adding the optional ISA430 digital output board.) The external input, and the line input (when BYPASS is pressed) are both fed to the A/D inputs, via the limiter, giving a clean, protected, high quality path to digital. Converter settings are as follows:

Clock Select

Selectable between 44.1kHz, 48kHz, 88.2kHz and 96kHz.

Bit Rate Select

Selectable between 24, 20 and 16 bits. 7

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Output Modes

POST MIC O/P

SEND RETURN
PRE INPUT SELECTION MIC LINE INST LEVEL TRIM & PHASE

INSERT SWITCHING MID EQ

FILTERS SHELF PARAM
DYNAMICS COMP GATE & DE-ESS
SWAP WITH DYNAMICS PRE EQ
Transformer O/P LEVEL LIMITER METER O/P OP1 Analogue Out
Int EXT I/P LIMITER METER Ext A/D CARD Digital Out
O/P MODE 1 - STANDARD Transformer O/P LEVEL SUM LIMITER METER O/P OP1 Analogue Out

EXT I/P

Mix External Signal into Internal Signal

A/D CARD

Digital Out O/P MODE 2 - SUM
Transformer O/P LEVEL INT DIRECT TO A/D O/P OP1 Analogue Out

LIMITER

METER A/D CARD Digital Out
METER O/P MODE 3 - A/D DIRECT

9:07 am

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Applications Super Clean Recording
This example shows the shortest possible (lowest distortion) analogue signal path from mic to tape. It bypasses all EQ and Dynamics functions.

Record Channel

This example shows the ISA430 being used for mic or guitar recording. The insert point may be used to add external processing in-line if required.
Record Digital with O/P Transformer in circuit *
This example shows how to record from Mic (or Line/Inst inputs) to the A/D, routing the audio through the output transformer. (In normal use, the Int A/D Direct input feeds the limiter and meter, then routing directly to the A/D card.) * Requires optional ISA430 Digital Output Board

Stereo A/D Converter

The optional A/D card is a stereo device which can convert two tracks simultaneously. Stereo conversion can be accessed by connecting the two audio signals into the EXT A/D DIRECT and INT A/D DIRECT inputs (directly accessing the A/D inputs via the limiter and digital meters). The INT input of the A/D can also be connected in the normal way via the Line I/P, if additional mono processing (EQ and Dynamics) were required on the signal, or if dual mono signals were being converted simultaneously. 9

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Split + Digital Record Mode *
This example shows the insert send feeding the External I/P A/D Direct input. This allows an analogue input to be connected to the insert return, and then routed, via the dynamics modules, to the digital output. * Requires optional ISA430 Digital Output Board.

Split Mix Down Mode

Switch unit to SPLIT. Insert 2 channels of console, one as EQ, the other as Dynamics. Mix down to digital using ISA430 A/D and Limiter section for high quality digital master
This example shows how to use the ISA430 in split mode as a mixdown tool. The ISA430 is simultaneously allowing EQ processing on audio from the console (CH1) and Dynamics processing on audio fromthe console (CH2) and allowing A/D digital conversion of the final mix fed from the master L/R console outputs. (Requires optional ISA430 Digital Output Board.)

Stereo ISA430 Units

A/D Card fitted
Send audio from second ISA430 to A/D Card in first ISA430. This configuration creates a stereo record channel with only one A/D Card required.

Stereo control of Dynamics section

No A/D Card fitted

This example shows how to link two ISA430s together, allowing them to be used as a stereo record channel. (Stereo dynamics processing and dual mono EQ (can be used as a stereo channel.)) The stereo channel can then be routed to a single optional ISA430 Digital Output Board allowing A/D conversion of the stereo signal. 10

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Specifications Rear Panel Connectors Insert Send
Connector: Signal: Operating Level: Maximum O/P Level: XLR Balanced +4dBu +26dBu
Input Impedance: Noise: THD:
10K -96dBu 0.003% with 0dBu 1kHz input and 20Hz-22kHz bandpass filter XLR Balanced(Transformer) +4dBu +26dBu -6 to +60dB in 6dB steps 1k2 123dB EIN with 150 at 60dB of gain 0.0008% XLR Balanced +4dBu +26dBu
Inserting the jack breaks the connection of the A/D input from the signal path and routes the signal from the jack directly to the A/D (Via the meter and limiter).
Gate Key I/P + Comp Key I/P
Connector: Signal: Operating Level: Maximum I/P Level: TRS (Stereo) Jack Balanced +4dBu +26dBu
Connector: Signal: Operating Level: Maximum I/P Level: Gain Range: Input Impedance: Noise: input resistance THD:
This output has two modes of operation: INSERT IN, the connector is an output from the point in the signal path determined by the Pre, Mid and Post selector and the Dyn Pre EQ button. SPLIT, the connector is the output of the dynamics section of the module.
Drives the sidechain of the gate or compressor.
Links two ISA430 units and control the dynamics section of both from one unit giving accurate stereo dynamics control.
Connector: Signal: Operating Level: Maximum I/P Level: XLR Balanced +4dBu +26dBu

Compressor

Threshold Range: Ratio: Slope: Attack: Release: (program dependent) -28dB to +12dB 1.5:1 to 10:1 Soft knee 100S to 100mS 100mS to 4S, variable or auto
Connector: Signal: Operating Level: Maximum O/P Level:
This input has two modes of operation: INSERT IN, the connector is the return or input to the signal path determined by the Pre, Mid and Post selector and the Dyn Pre EQ button. SPLIT, the connector is the input nto the dynamics section of the module.
Signal is routed directly from the Preamp after the gain stage, trim and phase reverse circuits of the input section and can be fed from the Mic, Line or Instrument

Limiter

Threshold Range: Ratio: Attack: 22dBu (infinity) Fast -40dB to +10dB 0 to -80dB switched fast or slow 100mS to 5S 20mS to 4S 0 to 5:1 22dBu 2K2 to 9K2 2:1
Connector: Signal: Operating Level: Maximum O/P Level: XLR Balanced (Transformer) +4dBu +26dBu

Inst. Hi Z I/P

Connector: Mono Jack Signal: Unbalanced (from any high impedance source such as guitar or bass pickups) Operating Level: -10dBu Maximum I/P Level: +10dBu Gain Range: +10 to +40dB Input Impedance: >1M

Threshold Range: Gate Range: Attack: Release: Hold: Expander Ratio:
Signal is the transformer output stage.

Ext A/D Direct I/P

Connector: Signal: Operating Level: Maximum I/P Level: XLR/Jack Balanced +4dBu +22dBu=0dBFs TRS (Stereo) Jack Balanced +22dBu=0dBFs
Threshold Range: Frequency Range: Ratio at Centre Frequency
Connector: Signal: Operating Level: Maximum I/P Level: Gain Range: XLR Balanced +4dBu +26dBu +/-18dB in 6dB steps

Int A/D Direct I/P

Connector: Signal: Maximum I/P Level:
Accuracy: Whilst every effort has been made to ensure the accuracy and content of this manual, Focusrite Audio Engineering Ltd makes no representations or warranties regarding the contents. Copyright: Copyright January 1999 Focusrite Audio Engineering Ltd. All rights reserved. No part of this manual may be reproduced, photocopied, stored on a retrieval system, transmitted or passed to a third party by any means or in any form without the express prior consent of Focusrite Audio Engineering Ltd.
Warranty: All Focusrite products are covered by a warranty against manufacturing defects in material or craftsmanship for a period of one year from the date of purchase. Focusrite in the UK, or its authorised distributor worldwide will do its best to ensure that any fault is remedied as quickly as possible. This warranty is in addition to your statutory rights. This warranty does not cover any of the following: Carriage to and from the dealer or factory for inspection or repair labour charge if repaired other than by the distributor in the country of purchase or Focusrite in the U.K.
Consequential loss or damage, direct or indirect, of any kind, however caused Any damage or faults caused by abuse, negligence, improper operation, storage or maintenance If a product is faulty, please first contact your dealer in the country of purchase; alternatively, contact the factory. If the product is to be shipped back, please ensure that it is packed correctly, preferably in the original packing materials. We will do our best to remedy the fault as quickly as possible. Please help us to serve you better by completing and returning the Warranty Registration Card at the back of this manual. Thank you.

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Focusrite Distributors
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Copy this template to record your own control settings for future use.

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Focusrite Audio Engineering Ltd, Lincoln Road, High Wycombe, Bucks HP12 3FX England Tel: +44 (0)FAX: +44 (0)1494 459920
e-mail: sales@focusrite.com www.focusrite.com

Introduction

Thank you for purchasing the ISA 430 MKII brought to you by the Focusrite team Ian, Trevor, Peter, Martin, Tom, Mick AC, Phil, Chris G, Micky, Pauline, Melissa, Chris W, Rob J Snr, Simon J, Vernon, Giles, Rob J Jnr, Mick G, Tim, Dave, Paul and Simon. The chaps at Focusrite are a jolly hard working bunch and take a great deal of pride in designing, building and delivering products which are considered to be the best audio units around; we hope your new Focusrite unit lives up to that reputation and that you enjoy many years of productive recording. If you would like to tell us about your recording experiences, please email us at: sales@focusrite.com
Important Safety Instructions
Please read all of these instructions and save them for future reference. Follow all warnings and instructions marked on the unit. Do not obstruct air vents in the rear panel. Do not insert objects through any apertures. Do not use a damaged or frayed power cord. Unplug the unit before cleaning. Clean with a damp cloth only. Do not spill liquid on the unit. Unplug the unit and refer servicing to qualified service personnel under the following conditions: if the power cord or plug is damaged; if liquid has entered the unit; if the unit has been dropped or the case damaged; if the unit does not operate normally or exhibits a distinct change in performance. Adjust only those controls that are covered by the operating instructions. Do not defeat the safety purpose of the polarised or grounding type plug. A polarised plug has two blades with one wider than the other. A grounding type plug has two blades and a third grounding prong. The wider blade or the third prong are provided for your safety. When the plug provided does not fit into your outlet, consult an electrician for replacement of the obsolete outlet. WARNING: THIS UNIT MUST BE EARTHED BY THE POWER CORD. UNDER NO CIRCUMSTANCES SHOULD THE MAINS EARTH BE DISCONNECTED FROM THE MAINS LEAD. This unit is capable of operating over a range of mains voltages as marked on the rear panel. Ensure correct mains voltage setting and correct fuse before connecting mains supply. Do not change mains voltage settings while mains supply is connected. To avoid the risk of fire, replace the mains fuse only with the correct value fuse, as marked on the rear panel. The internal power supply unit contains no user serviceable parts. Refer all servicing to a qualified service engineer, through the appropriate Focusrite dealer.

The Focusrite Team

Contents
Introduction.... 1 Contents... 1 Important Safety Instructions... 1 Power Connections... 1 Rear Panel Connections... 2 ISA 430 MKII Front Panel Controls.. 3 Metering.... 3 Input Stage... 4 EQ Module.... 5 Compressor.... 6 Gate.... 8 De-Esser... 9 Output... 9 Inserts and Routing Matrix...10 Soft Limiter...13 Optional Analogue to Digital Converter (ADC)..13 Digital Output Front Panel Controls...14 ADC Configurations...15 Mic Pre-amp Input Impedance...16 Applications...17 FAQs....21 Specifications...24 Accuracy...26 Copyright...26 Warranty...26 Reset Sheet...27 Focusrite Distributors..28

Power Connections

There is an IEC mains lead supplied with the unit which should have the correct moulded plug for your country. The wiring colour code used is: For units shipped to the USA, Canada, Taiwan and Japan: Live - Black Neutral - White Earth - Green For units shipped to any other country: Live - Brown Neutral - Blue Earth - Green and Yellow

Rear Panel Connections

(Optional A/D Card shown fitted)
XLR (Audio) Inputs and Outputs
All 3-pin XLR audio connectors (main and post-mic outputs, mic, line & ADC inputs, insert sends & returns) are wired as follows: Pin 1 Screen/chassis Pin 2 Audio 0 Pin 3 Audio 180

INSERT SEND 2

This is used as the insert 2 output point, or as the analogue output from the dynamics module in Dyn Split mode (see Dynamics Split diagram on page 10).

POST-MIC OUTPUT

This is used as an output from the point immediately after the Phase section (i.e. before EQ and dynamics modules) allowing direct recording of mic, line or instrument inputs. It provides a direct-to-tape, ultra-short signal path output. Taking a signal from the POST-MIC OUTPUT does NOT interrupt a signal routed from the mic-pre to the EQ, dynamics etc., so a direct feed to tape can be achieved whilst simultaneously allowing processing of the same source.

INST. HI Z INPUT

1/4 jack wired as follows: Tip Audio 0 Sleeve Screen/chassis

KEY INPUTS

1/4 jack wired as follows: Tip Audio 0 Ring Audio 180 Sleeve Screen/chassis

ADC INPUT 1

ADC Input 1 is used to route an external signal directly to the optional A/D card via the limiter. When selected using the ADC Input 1 button on the front panel, ADC Input 1 replaces the internal processed signal being fed to the left side of the A/D card (i.e. whatever is connected to the mic, line or instrument input no longer routes to the ADC). For further detail see ADC Input 1 & 2 on page 13. It also allows a signal to be summed with the processed signal from the unit by pressing the Ext Sum switch and using the Ext Level controls. This signal can be routed to the A/D card and main output (See ADC Input 1 & 2 on page 13.)

DYNAMIC LINK

1/4 jack wired as follows: Tip Compressor sidechain link Ring Gate sidechain link Sleeve Screen/chassis

MIC/LINE/INST INPUT

Any one of these inputs may be used as the main input to the ISA 430 MKIIs main input. Signals routed to these inputs are referred to as the Internal or Int signal path.

ADC INPUT 2

ADC Input 2 is also used to route an external signal directly to the optional A/D card via the limiter. When selected using the ADC Input 2 button on the front panel, ADC Input 2 replaces the internal unprocessed signal being fed to the right side of the A/D card (i.e. whatever is connected to the mic, line or instrument input). This still allows the processed signal (i.e. whatever is connected to the mic, line or instrument input) to route to the left side of the A/D card. Hence there are four possible setups for the ADC 1 & 2 input switches. (See ADC Input 1 & 2 on page 13.)

Listen LED

This illuminates when Listen is selected on the compressor, expander/gate or de-esser, and indicates that the unit is monitoring the selected sidechain frequencies. N.B. When attempting to listen to the dynamics in Split Dynamics mode, pressing the Listen switch will only result in visual monitoring; as the dynamics are split from the monitoring path, they can be viewed in the meter but not heard.

Meter Source

The VU meter can display input level, Insert 1 return level, Insert 2 return level, compressor gain reduction or sidechain Listen level. Press the Meter Source button to step through Input, Insert Rtn 1, Insert Rtn 2 and Comp sources as indicated by the corresponding LEDs. The sidechain Listen level will automatically be displayed on the

Audio O/L LED

This LED illuminates when the peak signal level reaches or exceeds +20dBu, or when the peak signal level reaches 6dB below the clip point. The signal is monitored at five points: post-the input gain Trim, post-Insert 1, post-the EQ
module, post-Insert 2, and post-the Dynamics module (since each module could cause clipping if incorrectly set up). Occasional short-duration peaks which may cause the LED to blink will not normally cause audible distortion, but if the LED is lit constantly, the level in the appropriate module should be reduced to prevent overloading.
legend). The gain range is split between two gain modes depending upon the status of the 30-60 switch: Mode 1: Mic Gain Range 0-30 With the 30-60 switch off, the rotary gain knob operates over a gain range of 0dB to +30dB, the level of gain chosen being indicated on the front panel by the outer arc of yellow numbers around the gain knob. Mode 2: Mic Gain Range 30-60 With the 30-60 switch on (illuminated), the rotary gain knob operates over a gain range of 30dB to 60dB, the level of gain chosen being indicated on the front panel by the outer arc of yellow numbers around the gain knob. An additional 20dB of gain can be applied to the signal after the Mic/Line gain knob using the Trim knob. See Trim control text below for full explanation.

Digital Output Meters

Two LED bargraph meters monitor the level being fed to the output (left meter) and input (right meter) of the unit. They also display the channels of the optional ADC card when the ADC Input 1 and ADC Input 2 switches are selected. The meters provide a wide range from 42dBFS (20dBu) to 0dBFS (+22dBu). The output meter monitoring point is just before the ADC input; this means that if the limiter is switched in the action of the limiter can be seen on the meter. This monitor point is also post-the output level control. When ADC Input 1 is selected the meter is fed from ADC Input 1. The input meter monitoring point is post-the phase switch. When ADC Input 2 is selected the meter is fed from the ADC Input 2.

Low Pass Filter

Sets a roll-off frequency from 400Hz to 22kHz.

High Pass Filter

Sets a roll-off frequency from 20Hz to 1k6Hz.
When the Comp switch is pressed, both Hi and Lo pass filters are inserted in the compressor sidechain to enable frequency-selective (aka frequency-conscious) compression. This selection is cancelled if Filter In or Gate is pressed.

Filter In

Press Filter In to make the Hi and Lo Pass Filters active in the audio path. This selection is cancelled if Comp or Gate is pressed. Both filters provide 18dB/octave roll-off, and since the filter frequencies overlap they may be configured as a very tight bandpass filter for creative compression and gating; use when you wish to select a specific instrument or narrow frequency band from a complex signal, then feed to the sidechain of the compressor or gate.
When the Gate switch is pressed both filters are inserted in the gate sidechain to enable accurate drum gating. This selection is cancelled if Filter In or Comp is pressed.

Parametric EQ

Two separate bands of parametric EQ, hi-mid and low-mid, are provided, each with continuously variable boost/cut with centre detent, sweep control with two ranges, and fully variable Q. The first band covers the range 40Hz to 400Hz (120Hz to 1k2Hz when x3 is pressed) and the second band covers 600Hz to 6kHz (1k8Hz to 18kHz when x3 is pressed).

Shelving EQ In

Press in to switch the shelving EQ into the signal path. This selection is cancelled if Gate or Comp is pressed.

Hi Range

The frequency controls have two ranges, the higher being selected when the Hi Range switch is pressed (frequencies shown in yellow on the panel).

LOW SHELF 33

HI RANGE

HIGH SHELF 655 2k2

Param EQ In
Press in to switch the parametric EQ into the signal path. This selection is cancelled if Gate or Comp is pressed.

20 0Hz

The Sweep controls have two ranges, the higher being selected when the x3 switch is pressed ( x3 frequencies are shown in yellow on the panel).

Low frequency shelving

The frequency range steps are 20Hz, 56Hz, 160Hz and 460Hz (33Hz, 95Hz, 270Hz and 655Hz when Hi Range switch is engaged).
When the Comp switch is pressed, the parametric EQ is inserted into the compressor sidechain, allowing frequencyselective (frequency-conscious) compression. This selection is cancelled if Param EQ In or Gate is pressed.

High frequency shelving

The frequency range steps are 1.5kHz, 3.3kHz, 6.8kHz and 15kHz (2.2kHz, 4.7kHz, 10kHz and 18khz when Hi Range is engaged).

When the Comp switch is pressed, the shelving EQ is inserted into the compressor sidechain, allowing frequencyselective (frequency-conscious) compression. This selection is cancelled if Shelving EQ In or Gate is pressed.
When the Gate switch is pressed, the parametric EQ is inserted into the gate sidechain for e.g. accurate drum gating. This selection is cancelled if Param EQ In or Comp is pressed.
When the Gate switch is pressed, the shelving EQ is inserted into the gate sidechain for e.g. accurate drum gating. This selection is cancelled if Shelving EQ In or Comp is pressed.

Shelving EQ

High and low frequency-shelving sections are available, each with continuously variable boost/cut with center detent, and a four position rotary switch for selection of roll-off frequency. In addition, the Hi Range switch allows for two ranges of roll-off frequency per band resulting in eight frequency selections in total.

Compressor

Comp In
Press Comp In to switch the compressor into the signal path. Note that the VU meter can be selected to display the compressor gain reduction (see Metering section, page 3).

Listen

Press to allow audio monitoring of the compressor sidechain to assist accurate frequency adjustment when setting up frequency-conscious compression. The Listen LED below the main VU meter illuminates to show that Listen mode is active. Note that the VU meter automatically displays the compressor sidechain listen level when a Listen switch is pressed in (see Metering section, page 3).

Vintage

The Vintage switch activates the vintage compressor. This has two modes, Comp and Lim, as indicated by the LEDs to the right of the Vintage switch. The Vintage switch steps through the different modes of compressor operation. In Comp mode the compressor is a vintage opto compressor. In Lim mode the compressor acts more like a vintage opto limiter with a harder ratio and knee. When neither the Comp or Lim LEDs are illuminated the compressor is in the classic Focusrite discrete Class A VCA mode. N.B. When in Vintage Comp or Lim mode the Attack, Release, Auto Release and Ext Key controls are inactive.

Attack

Attack determines how quickly compression is applied once the level of the source signal has risen above the threshold. When turned anticlockwise the response is very fast, which tends to make the compressor react to the peak levels of the signal. This is sometimes desirable, but can cause unwanted pumping of steadier low level components of the signal by short transients. A slower attack will cause the compressor to ignore short transients and respond more to the average loudness of the signal; however this may seem to increase relative volume of the transients.

Active LED Fast Attack

Fast Attack determines how quickly the gate opens once the level of the source signal has risen above the threshold. When the switch is pressed, the response is fast, which may be necessary on some signals to avoid missing an initial transient, but which could also introduce an undesirable click on smooth, sustained sounds when using a high threshold setting. On such signals a slower attack (switch released) may give a more natural sound. The Active LED illuminates when the de-esser is active at the chosen frequency, and shines more brightly with increasing level reduction.

Setting up the De-Esser

Press De-Ess Listen with Threshold at maximum and slowly reduce until the selected frequency begins to trigger the deesser. Vary the frequency control to find the exact area of the signal which you wish to remove. Once located, switch off De-Ess Listen and adjust Threshold for the amount of reduction required. No further adjustment of Freq should be required, as the hot spot will have been precisely found using De-Ess Listen.
Press to introduce wider hysteresis. This increases the level difference between the gate switching on and off, which prevents the gate from oscillating (chattering) with particular combinations of input signal and threshold setting. This function is particularly useful when gating a signal with a very long decay time and large amounts of level modulation (e.g. a grand piano).

Output

Ext Sum
Press to route a sum of both the internal signal and external line input signal (from the EXT SUM INPUT) to the Main Output. External signals could
Pressing Ext Key switches control of the gate to an external signal on the rear panel GATE KEY INPUT jack.
be a double track, an extra mic from a second ISA 430 MKII, or live reverb.
Press to mute the output of both the Main Output and Post-Mic Output. N.B. Analogue sends and digital outputs are not muted.

Ext Level

This control adjusts the gain of the external line input which may be summed into the Main Output (see above).

Bypass

All EQ and dynamics processing modules can be globally switched out using the Bypass switch, for quick A/B comparison of processed/unprocessed signals.

Adjusts the Main Output level between -60dB and +6dB.
Inserts and Routing Matrix
The ISA 430 MKII has two insert points and a very comprehensive set of routing options.

Insert 1

Activated by the Insert 1 In switch. The insert 1 send and return are both balanced XLRs and are situated post- the Phase switch. Insert 1 Send and Return always remain pre- any of the processing sections (EQ, dynamics etc).

EQ Split

Activated by the EQ Split switch. This allows the INSERT SEND 1 and INSERT RETURN 1 connections to act as inputs and outputs to the EQ section only, thus giving a separate line level EQ unit, which acts independently from the dynamics processing. When EQ Split is selected, the Insert 1 switch, if lit, wll go out. This is because Insert 1 is now being used as the input and output to the EQ section, and so is no longer available for use as a traditional insert. Using Insert 1 to split EQ:
Using Insert 1 as traditional insert:

MIC LINE INST

INSERT 1 SEND

INSERT 1 RETURN

LEVEL TRIM & PHASE

DYNAMICS

Dynamics Split
Activated by the Dyn Split switch. This allows the INSERT SEND 2 and INSERT RETURN 2 connections to act as independent inputs and outputs to the dynamics section only, thus giving a separate line level dynamics unit. When Dyn Split is selected, the Insert 2 and Post-Dyn switches, if lit, will go out. This is because Insert 2 is now being used as the input and output to the dynamics section, and so is no longer available for use as a traditional insert. Using Insert 2 to split dynamics:

INSERT 2 RETURN

INSERT 2 SEND

EXT SUM

O/P LEVEL

LIMITER

ANALOGUE OUTPUT ADC METERS

Dynamics position switch

Allows the dynamics section to be placed in three different positions in the processing chain. (Normally the dynamics section is the second processing section in the signal path, after the EQ section.) When activated, the new position of the dynamics section is indicated by the LEDs below the Dynamics switch.
a) Dynamics Post-EQ (Default)
b) Dynamics Pre-EQ Pressing Dynamics once reverses the position of the EQ and dynamics sections, placing dynamics first and EQ afterwards. The Pre-EQ LED illuminates to provide visual confirmation of the dynamics pre-EQ position.

Note: cables need to be purchased separately. Since there are two different cable options XLR for AES and RCA phono for SPDIF these are not included with the A/D converter options. Focusrite cables may be purchased from your local dealer. If you experience difficulty in obtaining these cables, contact your local distributor as listed in the back of this manual.
makes the ISA 430 MKII useable with both old and new equipment.

Word Clock In and Out

The internal ADC can be synchronised to an external word clock. By pressing the front panel Ext Sync switch, the ISA 430 MKII can be switched to lock to either standard external word clock or 256X external word clock. Either type of external word clock should be connected to the ISA 430 MKII ADC card at the WORD CLOCK IN BNC connector. The WORD CLOCK OUT BNC connector either regenerates the external word clock connected at the word clock input connector (if locked to an external clock source) or transmits the internal sample frequency of the ADC card (if the ISA 430 MKII is acting as word clock master). Where the ISA 430 MKII is being used as a slave device within a larger digital system, the WORD CLOCK OUT BNC connector can be used to pass on the external word clock signal to the next device. When the unit is not slaved to another device and is in internal clock mode, the word clock output connector outputs the sample frequency selected on the ISA 430 MKII front panel.
AES/SPDIF Connector Configuration
The 9-pin D-type connector labeled AES/SPDIF can be configured either as an AES or SPDIF dedicated output using the AES/SPDIF switch next to it. When operating the connector in AES mode an AES cable is required. When operating in SPDIF mode the SPDIF RCA cable should be used, which automatically sets the output stream to consumer mode. The 1 Wire/2 Wire switch selects 1 wire or 2 wire mode for the AES output as follows:
1 WIRE MODE AES XLR BREAKOUT CABLE

CH 1+2

9 WAY D-TYPE

YELLOW

Digital Output Front Panel Controls

Clock Select

2 WIRE MODE

AES XLR BREAKOUT CABLE

Pressing this switch allows the user to select between sample frequencies of 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, and 192kHz.

Bit Depth Select

Pressing this switch allows the user to select between 24-, 20- and 16-bit depths.
1 Wire mode Selected with the switch in the out position. The AES connector transmits two channels of AES data simultaneously for all sample frequencies from 44.1 to 192kHz, over a single wire. 2 Wire mode Selected with the switch in the in position. The AES connector transmits one channel of AES data only per cable, for all sample frequencies from 96kHz to 192kHz. The reason for the two modes is that older equipment with 96kHz and 192kHz AES inputs can only receive speeds up to 192kHz by using both digital channels of a single AES connection (known as 2 wire). Therefore one AES channel can send only a single channel of digital data. This switch

Ext Sync

Pressing Ext Sync allows the ISA 430 MKII to be slaved to an external word clock source. Selecting 256X allows the ISA 430 MKII to be slaved to an external clock running at 256 times faster than the sample frequency and enables connection to systems such as the Digidesign 'Superclock' or other 256 slave clock devices.

Lock LED

When lit, LOCK indicates that the unit is synchronised to an external clock source.

ADC Configurations

Analogue recording with digital conversion

INSERT 2

INSERT 1

ANALOGUE O/P

1 EQ DYNAMICS O/P LEVEL SOFT LIMITER DYN PRE EQ SWAP DYN POST SUM SWAP OUTPUT METERS INPUT 2 ADC DIGITAL O/P

POST MIC OUTPUT

(In this example both ADC 1 and ADC 2 switches are unlit and Soft Limiter is switched in.)
Analogue recording and stand-alone stereo ADC conversion

DYN PRE EQ SWAP

DYN POST SUM SWAP POST MIC OUTPUT ANALOGUE O/P
ADC 1 I/P SOFT LIMITER ADC 2 I/P METERS

DIGITAL O/P

(In this example both ADC 1 and ADC 2 switches are lit and Soft Limiter is switched in.)
Mic Pre-amp Input Impedance
A major element of the sound of a mic pre-amp is related to the interaction between the specific microphone being used, and the type of mic pre-amp interface technology to which it is connected. The main area in which this interaction has an effect is the level and frequency response of the microphone, as follows: Level: Professional microphones tend to have low output impedances, so more level can be achieved by selecting the higher impedance positions of the ISA 430 MKII mic pre-amp. Frequency response: Microphones with defined presence peaks and tailored frequency responses can be further enhanced by choosing lower impedance settings. Choosing higher input impedance values will tend to emphasise the high frequency response of the microphone connected, allowing improved ambient information and high end clarity, even from averageperformance microphones. average microphone, around 1.2k to 2k. (The original ISA 110 pre-amp design followed this convention and has an input impedance of 1.4k at 1kHz.) Input impedance settings greater than 2k tend to make the frequency-related variations of microphone output less significant than at low impedance settings. Therefore high input impedance settings yield a microphone performance that is more flat in the low and mid frequency areas and boosted in the high frequency area when compared to low impedance settings. Ribbon microphones The impedance of a ribbon microphone is worthy of special mention, as this type of microphone is affected enormously by pre-amp impedance. The ribbon impedance within this type of microphone is incredibly low, around 0.2, and requires an output transformer to convert the extremely low voltage it can generate into a signal capable of being amplified by a pre-amp. The ribbon microphone output transformer requires a ratio of around 1:30 (primary: secondary) to increase the ribbon voltage to a useful level, and this transformer ratio also has the effect of increasing the output impedance of the mic to around 200 at 1kHz. This transformer impedance, however, is very dependent upon frequency - it can almost double at some frequencies (known as the resonance point) and tends to roll off to very small values at low and high frequencies. Therefore, as with the dynamic and condenser microphones, the mic pre-amp input impedance has a massive effect on the signal levels and frequency response of the ribbon microphone output transformer, and thus the sound quality of the microphone. It is recommended that a mic pre-amp connected to ribbon microphone should have an input impedance of at least 5 times the nominal microphone impedance. For a ribbon microphone impedance of 30 to 120 the ISA 430 MKIIs input impedance of 600 (Low) will work well, and for 120 to 200 ribbon microphones the input impedance setting of 1.4k (ISA 110) is recommended.

UNIT A: NO ADC CARD FITTED

UNIT B: ADC CARD FITTED

STEREO CONTROL OF DYNAMICS
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 EQ processing of audio, plus separate dynamics processing of audio. At the same time it is allowing two channels of A/D conversion into a DAW as well as allowing super clean microphone recording! (Requires optional ISA 430 MKII digital output board.)
RETURN MIXER INSERT CH 1 SEND RETURN MIXER INSERT CH 2 SEND IN OUT IN OUT EQ POST MIC OUTPUT MIC INPUT
Using Ext Sum to record a single source with two mics
This example shows an analogue output from Focusrites ISA 428 mic pre-amp routed into the EXT SUM Input on the ISA 430 MKII. The EXT SUM switch is on and the signals levels are being balanced using the Ext Level control. The Dynamics switch has been pressed to select Post-Sum. This shows how to record a single source such as a snare drum with two microphones, summing the signals together and then processing with the dynamics section.

SOUND SOURCE

OUTPUT INPUT MAIN OUTPUT ISA 428 MIC INPUT

EXT SUM INPUT

1. Are the EQ and Dynamics the original Focusrite designs? Yes; the mic pre-amp, hi- and lo-pass filters, EQ, compressor, and expander/gate are all based on those used in the original Focusrite console. However, the circuitry has been expanded to incorporate new features; the ISA 110 EQ having additional frequency options for its shelving and the compressor now including opto-circuitry and extra routing and controls. Plus, the mic pre-amp has a variable impedance and new selectable air effect. 2. Is the ISA 430 MKII a Class A device, and why is that important? Yes, the 430 MKII is a Class A device. Why? Well, Class A is a type of amplifier design in which you have a standing DC current running through your amplifier circuits all the time. As the signal comes along you vary what you're taking from that, rather than switching between supplying a positive current for one half of the waveform and a negative current for the other half. This results in the ability to represent audio in a linear (distortion free) manner all the way through the circuit. Cheaper processors use IC amplifiers which run close to Class B and don't have the same standing DC current, which means the transistors inside the chips switching off and on, inevitably resulting in less linear performance. 3. What does the Vintage compressor button involve? In addition to the Class A VCA circuit, the vintage optical circuit adds a whole new flavour of compression. The vintage circuit operates in two modes, as a compressor character or as a limiter. The attack and release are fixed when using the opto-circuit and the threshold point is raised/the knee hardened when compressing with the limiting characteristics selected. 4. So the compressor contains both VCAs and optical technology? Yes. Whilst the expander and gate use solely VCAs and the de-esser and limiter are optical. 5. Ive heard of the pumping effect that sometimes occurs when a signal is compressed. How can it be avoided? If the release time is too short, the signal level may pump in other words, you can hear the level of the signal going up and down. However, a release time that is too long will result in the level of quiet sounds following a loud beat to be reduced even further. In addition, having the threshold set below the level of the kick drum and the release time set relatively long will punch holes in the track as the level drops with each beat. If the release time is adjusted to be much faster then an entirely different, dynamic-sounding mix can be produced. As a rule, a good starting point for release time lies between 0.2 and 0.6 seconds. 6. What can the inserts do? Both inserts are split-configurable. This means that insert 1 can split the EQ from the signal path if the option is selected and insert 2 can split the dynamics. Also, insert 2 is flexible as to signal positioning and defaults to pre-dynamics but can move to post- if desired. 7. What if I want my dynamics processing to occur pre-EQ or post-sum? No problem; the dynamics section can be switched so that it precedes the EQ section by a single push of the Pre-EQ button on the front panel. Pressing the Post Sum button places the dynamics section after the Ext Sum input. See Inserts and Routing Matrix on page 10 for more details. 8. Is there any way to configure the ISA 430 MKII as a stereo unit? Yes; although a single ISA 430 MKII can act only as a mono or split mono unit, its possible to link two MKIIs together, using the dynamic link socket on the rear panel. Using a single stereo TRS jack cable, this allows stereo operation of the compressor, plus dual mono EQ. You can also use a single ISA 430 MKII as a stereo A/D converter. See question 16 below for a full explanation. 9. How do I control which ISA 430 MKII will be the controller and which will be the slave when using two together for stereo compression? Whichever ISA 430 MKII is generating the greater control voltage will be the controller. So, set one of the MKIIs compressors to minimum ratio and maximum threshold, and the other compressor will then always be the controller, with any changes made on the controller knobs affecting both channels in the same way. 10. Can I wire the link cable to just link the compressors or gates? Yes; the compressors are linked from tip to tip and the gates from ring to ring of the TRS jack lead. So, leaving the sleeves connected and disconnecting either of those lines will enable the other to function as a stereo pair alone (whilst the disconnected one will act individually, as two separate comps/gates, on each mono signal). 11. I own an ISA 430. Can I link the dynamics to a MKII for use as a stereo pair? Yes; simply connect a link cable as described above. N.B. the ISA 430 MKIIs compressor must be set to VCA mode. 12. Does the ISA 430 MKII have the same kind of spectacular bandwidth that has given the Red range its reputation for open-ended sound? Yes. The bandwidth of the ISA 430 MKII is 10Hz to 200kHz! 13. Can I use all the different sections of the ISA 430 MKII at once? Yes. If you want to use the mic pre, hi- and lo- pass filters, parametric and shelving EQ, compressor, expander/gate, deesser, limiter and digital output all at the same time, as one huge super channel, you can. You can also take any section out of the signal path independently with a single button push. Or you could use the ISA 430 MKII in split mode.

14. What is split mode? Split mode allows the ISA 430 MKII to act as separate processors at the same time, handling totally separate audio signals. So one channel of audio can be routed through the EQ sections, with a second, discrete audio channel being routed through the dynamics sections. Furthermore, if the mic pre-amp is also being utilised to output direct to a recording format as well as the ADC dealing with 2 further signals, the unit is acting as four separate processors at once! 15. Can I route any EQ sections to the dynamics? Yes: the hi- and lo- pass filters, the low-mid and hi-mid parametric EQ, and the hi- and lo- shelving EQ can all be routed independently to the sidechain of the compressor, or to the sidechain of the gate. This means that you can control the action of the compressor the gate from any individual section of EQ (frequency selective compression). Also, you have a listen button in the compressor, gate and de-esser sections, which allows you to monitor whatever is feeding the sidechain of each section so that you can easily hear and tune the frequency you want to trigger each dynamics processor. Theres even a separate listen LED by the main meter to warn you that you are listening to something other than the main output like a PFL warning light on a mixing console. The VU meter can also be selected to view the sidechain for additional control. 16. Can I use the ISA 430 MKII as a 24bit/192kHz stereo A/D converter? Yes the external input, plus the line input (bypass on) or the ADC inputs can be used as a stereo feed to the optional A/D converter. They also pass through the soft limiter before reaching the A/D, preventing digital clipping. 17. What if I want to use the mic pre-amp in isolation? Theres a Post-Mic Pre-output which allows you to take signal out of the ISA 430 MKII from a point immediately after the mic pre. Using the ISA 430 MKII in this way provides a very short signal path to tape, for ultra-clean recordings. Also, connecting the Post-Mic Pre-output does not interrupt the signal flow from mic pre-to EQ, dynamics etc, so a direct feed to tape can be achieved whilst simultaneously allowing processing of the same source signal. 18. The Air switch sounds great but whats actually happening to my signal? This feature increases the impedance effect of the transformer on high frequencies, adding further air to its sonic quality. It does this by including an inductor circuit into the secondary of the transformer, giving the pre-amp an input impedance that varies with the frequency, having a smaller voltage drop at the top-end. So, additional clarity is introduced by the interaction between the mic and pre-amp alone, without EQ. 19. What if I experience problems with the gate chattering? The ISA 430 MKII is equipped to deal with this simply pressing the Hyst button, which introduces hysteresis,

feeds any Digi interface as above. So if a customer wants to use an ISA 430 MKII, but at the same time varispeed Pro Tools, they need a Superclock input. 24. Is there an optional digital input card? No, because all the processing in the ISA 430 MKII is entirely analogue so even if there was a digital input, the digital signal would have to be immediately passed through a D/A converter to allow processing! 25. Does the card include dithering? Yes, the wordlength of a 24-bit input can truncated down to 20 or 16 bits and then dithered prior to digital output. 26. Why are the Int. A/D and Ext. A/D inputs fed to the digital output card via the limiter? The input to the A/D converter must not exceed 0dBfs in order to prevent digital clipping. The limiter therefore comes after the A/D converter inputs so that the user is protected from digital clipping. 27. Can I lock straight to Pro Tools from the digital output of the ISA 430 MKII? Yes, the digital output board is designed so that it can synchronise to external word clock signals, or to Digidesign's Superclock. 28. Why is the 24-bit 192kHz specification important? An A/D converter works by sampling the audio waveform at regular points in time, and then quantising those values into a binary number, which relates to the number of bits specified. The quantised signal must then be passed through a D/A converter before it becomes audible. In simple terms, the D/A essentially joins the dots plotted by the A/D converter when the signal was first converted to digital. The number of dots to join, combined with how little those dots have been moved, determines how accurate the final signal will be compared to the original. The greater the sample rate and bit rate, the more accurate the whole digital process is. So 24-bit/192 kHz performance will ensure more accurate digital transfer of your audio
information compared to the old 16-bit/ 44.1kHz standards. (You can still use these standards for compatibility reasons if you need to as the ISA 430 MKII also allows 16-bit/44.1 kHz operation.) 29. Can I retrofit a digital board to an analogue ISA 430 MKII at a later date? Yes, you can do it yourself it can easily be retro-fitted by the customer without any soldering etc. just a few screws to undo, and one clip-connector to join to the main PCB. 30. What are the differences between the ISA 430 MKII and the ISA 430? The MKII has variable mic pre-amp impedance, as featured on the ISA 428 Pre-Pack, allowing the performance of the unit and microphone connected to be tailored to a suitable level and response. The MKII runs up to 192kHz, with 1and 2-wire modes selectable at the rear plus SPDIF available on optical cable. The MKII has dBFS metering on the right hand side with optional viewing of the ADC inputs, as well as a VU meter with selectable calibration and additional sidechain view. The compressor on the new model has a variable blend, with a dial to adjust the mix, and contains VCA and optocircuitry. The limiter-configurable nature of the opto means there are a total of three types of compressor. Also, the auto release now has its own dedicated switch and the compressor can be positioned post-sum or pre-EQ. The soft limiting of the MKII can be used on analogue and digital outputs simultaneously. The MKIIs shelving includes 2 extra frequencies per band: 20 and 655Hz for LF and 1.5 and 2.2kHz for HF. The mic pre-amp transformer features an optional inductor circuit for boosting HF and adding air to the signal, and its gain controls are identical to the ISA 428. There are two inserts on the MKII, both being splitconfigurable with movable routing facilities. Lastly, the MKIIs ADC inputs are both XLR and the line input is now routed through the input transformer as with the ISA 220 and 428.

Line input Connector: XLR Signal: Balanced Operating Level: +4dBu Gain range = -20dB to +10dB in 10dB steps Input Impedance = 10k from 10Hz to 200kHz Noise at main output with gain at unity (0dB) = -91dBu measured with a 20Hz/22kHz bandpass filter Signal to noise ratio relative to max headroom (28dBu) = 119dB Signal to noise ratio relative to 0dBfs (+22dBu) = 113dB THD at unity gain (0dB) =.002% measured with +4dBu input signal and with a 20Hz/22kHz bandpass filter Frequency Response at unity gain (0dB) = 0.25dB down at 20Hz and 3dB down at 140kHz Instrument input Connector: Mono Jack Signal: Unbalanced Gain range = 10dB to 40dB continuously variable Input Impedance = >1M Noise at minimum gain (0dB) = -90dBu measured with a 20Hz/22kHz bandpass filter Noise at maximum gain (40dB) = -78dBu measured with a 20Hz/22kHz bandpass filter THD at minimum gain (0dB) =.006% measured with 10dBu input signal and with a 20Hz/22kHz bandpass filter Frequency Response at 10dB gain = 0.2dB down at 26Hz and 0dB at 32kHz
Main Output Connector: XLR Signal: Balanced Operating Level: +4dBu Maximum O/P Level: +26dBu Dynamic Link Connector: TRS Jack Signal: Tip = Compressor, Ring = Gate Links two ISA 430 MKII units to allow control of the dynamics section of both units from one unit giving accurate stereo dynamics control Gate Key I/P + Comp Key I/P Connector: TRS (Stereo) Jack Signal: Balanced Operating Level: +4dBu Maximum I/P Level: +26dBu Drive the sidechains of the gate and compressor respectively. N.B Comp Key I/P is not available in Vintage mode. ADC Input 1/Ext Sum Input Connector: XLR Signal: Balanced Operating Level: +4dBu Maximum I/P Level: +22dBu=0dBFs in ADC input mode, +26dBu in Ext Sum input mode ADC Input 2 Connector: XLR Signal: Balanced Maximum I/P Level: +22dBu=0dBFs EQ (Shelving) Gain range: +/-18dB LF: 20Hz, 56Hz, 160Hz, 460Hz LF (Hi Range in): 33Hz, 95Hz, 270Hz, 655Hz HF: 1k5Hz, 3k3Hz, 6k8Hz, 15kHz HF (Hi Range in): 2k2Hz, 4k7Hz, 10k, 18k EQ (Parametric) Gain range: +/-18dB Variable Q LMF: 40-400Hz LMF (x3 in): 120-1200Hz HMF: 600-6kHz HMF (x3 in): 1k8-18kHz EQ (Filters) 3rd Order 18dB/Octave LPF: 400Hz-22kHz HPF: 20Hz-1k6Hz Compressor (Class A VCA mode) Threshold Range: -28dB to +12dB Ratio: 1.5:1 to 10:1 Slope: Soft knee Attack: 100S to 100mS Release: 100mS to 7S, variable or auto (program dependent)