FOCUSRITE ISA 428 FOUR CHANNELS MIC PREAMPLIFIER

Overview:

The ISA 428 Pre Pack is the perfect multi-channel front end for any professional DAW.
Four classic Focusrite transformer-based pre amps with switchable impedance and direct
instrument inputs. An optional eight channel 192kHz ADC, preceded by the all new proprietory
Soft Limiter circuit, provides the perfect path into your Pro Tools HD system.
The benefits of the pre amp's topology include superb common-mode rejection, an excellent
overload margin and, with its 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 (10Hz to
200kHz). This pre amp design is the cornerstone of Focusrite's signature 'warm-yet-transparent'
sound and is a point of reference for any discerning audio professional.
In addition, the input stage provides enhanced control and creativity allowing you to switch between
four carefully selected input impedance settings. The original ISA 110 setting is supplemented by
three further impedance settings to either perfectly match the pre amp with any microphone and
maximise level, or use different settings creatively to shape the sound of the microphone being used.
Should the need arise to place extra processing in between pre amp and conversion, insert points are
also featured on every channel.
Protecting the ADC, the Soft Limiter opto circuit is a new design from Focusrite, entirely preventing any
'digital overs', whilst minimising the undesirable distortion that standard limiter circuits often generate.
Finally, the new ADC embodies cutting-edge conversion technology, encompassed within pristine Focusrite
circuitry, providing eight conversion channels of the highest quality, at frequency rates of up to 192kHz.
Running at 96kHz allows for up to 16 (2 x 8, parallel) simultaneous digital outputs in addition to the four
main analogue outputs. Digital output options include dual AES/EBU, SPDIF and dual ADAT lightpipe.
Full digital metering is provided for every channel, alongside new 'moving coil' peak meters, designed to
catch even the fastest of transients.
A second analogue unit can be connected utilising the four extra ADC input channels on the rear of the unit
containing the optional ADC. This makes full use of the eight channels provided on a single optional ADC and
expands your front-end capacity from four pre amps and eight digital outputs to eight Pre amps and eight digital
outputs.
Classic preamp technology, custom Focusrite input and limiting circuits and the very best in A/D conversion
technology, the ISA 428 Pre Pack raises the bar for multi-channel recording solutions into Pro Tools HD, or any
other professional DAW. Equally, it can be used as an additional set of high quality pre amps for any analogue
or digital console or hard disk recorder.
Four classic Focusrite transformer-based preamps.
8 channels of cutting-edge A/D conversion, running at up to 192kHz. Protected by proprietory optical Soft Limiter
circuit.
Switchable Impedance for unparalleled mic matching or extended mic creativity - includes the classic ISA 110
setting.
Multiple Front Panel Instrument DI. No separate DI box required.
Analogue insert points on every channel.
High Pass Filters on every channel.
New moving coil peak meters & full digital metering (dBfs).

ADAT is a trademark of Alesis Corp
Pro Tools HD is a trademark of Avid Technologies plc.
The 192kHz ADC is an extra cost option.

Specifications
Inputs
Transformer-based ISA design
Gain range: Line = +/- 18dB, Mic = 0 to 60dB (both in 6dB steps), Inst = +10 to +40 dB
variable
Input impedance: Line = 10k ohm, Mic = Variable - 600, 2k4 and 6k8 ohm + original ISA 110
settings, Inst = >1M ohm

Analogue Performance
Noise: Line = -96dB, Mic = -128dB (EIN with 150 ohm input resistance at 60dB of gain)
THD: Line = 0.003% with 0dBu, 1kHz input and 20Hz to 22kHz band-pass filter, Mic = 0.003%

Analogue Input and Output connectors (balanced)
D.I inputs: 1/4 inch Jack (unbalanced)
Mic inputs: XLR (balanced)
Line: TRS Jack (balanced)
Insert Sends and Returns: TRS Jack (balanced)
Additional ADC inputs: XLR (balanced) Line level
Analogue Outputs: XLR (balanced)

Digital Output Option
AES/EBU and S/PDIF dual 9-pin D-types
Optical - ADAT Lightpipe
Bit depths 16-, 20- or 24-bit
Frequency options 44.1, 48, 88.2, 96, 176.4 and 192kHz
Clock options Standard or ?256 x?
Meter - 0 dBFS = +22dBu
Digital Performance
SNR - 120dB A-weighted

The AD2022 is Avalon's fourth generation of fully discrete, symmetrical Pure
Class A microphone preamplifiers. The dual mono AD2022 includes the original
sonic capabilities and transparency of the M2, M22 and M5 preamplifiers plus
several additional features, including selectable microphone source loading for
optimized cable/mic matching, improved high-voltage Class A regulated power
supplies, two high Z instrument inputs, variable-passive high pass filter, teflon/
silver wiring and doubled plated circuit boards for superior low level signal transfer.
 
AD2022 FEATURES
Symmetrical Pure Class A design, two channels
Microphone and hi-Z instrument inputs
Gain switched 4dB steps plus +/- 3dB fine output trim 
Selectable microphone input impedance matching 
Low noise -126dB EIN
Ultra high quality, low-ratio, balanced input transformer
Balanced, high-current Class A output to +36dB
Large illuminated analog VU meters and twin peak LED's
Regulated phantom power supply +48v 
Input polarity phase reverse 
High headroom +36dB input before overload
Input -20dB pad for high level signals
Sealed silver relays for all signal routing
External AC 150w toroidal power chassis
Fully discrete Class A regulated audio power supplies
Deep, musical sound-stage, transparent amplification

MICROPHONE INPUT
The AD2022 incorporates the most advanced high-performance microphone
transformer available. Split low-ratio primary windings are carefully combined
within a custom mu-metal core for extended smooth frequency response and
very low distortion.  Sealer silver relays are used for minimal signal invasion. 
The input signal selector, high pass filter, polarity-phase reverse, +48v power
and the 20dB input attenuator all utilize local sealed relay operation. A variable
passive high pass filter provides a minimum phase shift design while eliminating
low frequency rumble, wind noise and mechanical vibration at sub sonic frequencies.

SYMMETRICAL PURE CLASS A DESIGN
Two 100% discrete, high-voltage, symmetrical Pure Class A signal amplifiers
are utilized per channel. The first operates in a cascaded-cascode FET
configuration while the second stage amplifier is fully bipolar. The twin amplifiers
share the total available gain requirement. This shared architecture increases
the high level headroom capability, improves transient response and doubles the
internal bandwidth of the ultra-high performance pure Class A signal amplifiers.
OUTPUT and METERING
High-current DC coupled, Class A discrete amplifiers are utilized for the output
drive interface with +36dB capability into all known loads.  Two large, high-quality
analog VU meters indicate accurate signal readings while bi-color LED's offers
peak indication at 0dB and +20dB.

AD2022 PREAMPLIFIER SPECIFICATIONS
 
Circuit Topology:  Twin cascode FET and bipolar low level signal amplifiers,
high-voltage, 100% discrete, symmetrical Pure Class A 
Input Type and Load:  Transformer balanced low-ratio, 50, 150, 600 and 1k5
ohm input load selection  
Maximum Mic Level:  +36dB balanced XLR pin 2 hot (with -20dB passive
attenuator) 
Maximum Instrument Level  +18dB at 100k ohms instrument input level,
standard mono 1/4 inch jack 
Input Attenuator:  -20dB resistive pre transformer primary, sealed silver relay 
Phantom Power:  +48v regulated 50mA capability, sealed silver relay 
High Pass Filter:  Passive, variable from 30Hz to 185Hz @ 6dB per octave,
sealed silver relay. 
Polarity Reverse:  Sealed silver relay on microphone input 
Gain Range Input:  +20dB to +64dB in 4dB steps 
Gain  Output Range:  +/- 3dB variable conductive plastic potentiometer 
Maximum Output Level:  +36dB balanced 600 ohms, DC coupled, discrete
symmetrical Pure Class A 
Output Type:  XLR connector, pin 2 hot 
Noise EIN Unweighted:  -126dB 150 ohm 
Noise 20kHz Unweighted:  -102dB 
Distortion THD, IMD:  0.05% nominal 
Frequency Response -3dB:  1Hz to 120kHz transformer limit 
System Bandwidth:  DC to 1MHz 
Output Meter:  High quality, illuminated analog VU meter 0dB = +4dB. 
Peak Meter:  Bi-color LED's 0dB and +20dB peak detection circuit. 
AC power supply B2T:  External toroidal 100V to 240V, 50-60Hz selectable,
150 watts maximum. 
Cables:  90V ac, 4 pin male power input connector, B2T required, internal
DC regulation  
Dimensions:  19 x 12 x 3.5 in (482 x 305 x 89mm) 
Weight:  15lbs (6.8kg) 
Dimensions - Shipping Carton:  24 x 21.5 x 7.5 in (610 x 546 x 190mm)  
Weight - Packed:  25lbs (11.4kg) 

The PRE-73 Mk2 is the first one-channel low-cost preamp on the market that is using a fully discrete signal path with three separate transformers for the balanced mic input, the line input and the output.

The circuit is very similar to the classical preamp section of the Neve 1073 pre/eq module with a corresponding sound character that is warm, punchy, sweet and musical.
This classical sound has been heard on countless recordings through the years and it is a versatile sound that works very well on most sound sources and in most genres.

The PRE-73 Mk2 has a maximum gain of 80 dB on the mic input and the gain range on the Line input is -20 to + 10 dB. There is also a high-impedance instrument input.

The PRE-73 Mk2 is perfect for almost any signal source, no matter if it's a microphone with a high or low sensitivity (like a passive ribbon mic), a syntheziser or sound module or an electric guitar or bass.

The input impedance of the microphone input can be switched between 300 and 1200 ohms, which makes it possible to affect the tone of most microphones. There is also phase switch and an simple 4-step LED signal level meter.

The output level control makes it possible to make fine gain adjustments and also to overload the main gain stage for more character and then lower the signal to a suitable level before the output stage.

The Mk2 update consists of:
- An unbalanced insert jack (nominal level about 18 dBu) added on the back panel for inserting units like the coming GAP EQ-73, a three band eq.
-  LED meter levels adjusted.
- 600 Ohm termination resistor and jumper added to power supply board (accessible from the inside of the unit).
- Revised Gain switch, turning the know clockwise now increase the gain.
- Reduced noise at high gains by a change to the power supply grounding scheme.

 The OctaMic II provides 8-Channel 192 kHz / 24 bit AD conversion with eight hi-class microphone and line pre-amplification channels, featuring a combination of sophisticated components and approved RME technology.

Lowest distortion, excellent signal to noise ratio and perfectly linear frequency response transmit and amplify the microphone signals truly unchanged.

The OctaMic II includes some significant enhancements compared to the OctaMic:

The balanced TRS inputs of the Neutrik Combo XLR jacks are phantom power-free and can be operated as real line inputs too. The improved design of the input circuits allows for a maximum input level of +21 dBu with a convenient gain range from 6 dB up to 60 dB.
Improved signal to noise ratio (SNR) ADC 107.5 dB
Improved THD, especially at higher gains
Optimised heat dissipation by a new and larger housing with improved convection
Internal wide range power supply with line filter, insensitive to voltage fluctuations
Super-stable, short circuit proof 48 V phantom power


Features

OctaMic II offers 8 balanced XLR mic / line inputs via Neutrik XLR/TRS combo jacks. Each channel contains switches for 48V phantom power, a low cut filter and phase reversal. Amplification can be set between 6 and 60 dB. LEDs for signal, clip, and activated phantom power give a complete overview on the unit's status. When the special Clip Hold mode is activated, any detected clip-state will cause the corresponding LED to flash once per second. With this, the user gets a long-term peak detection, and no longer needs to constantly watch the LEDs. At the same time momentary overloads are still displayed correctly.

Frontside switches include power on/off and output level, for a choice of -10 dBV, +4 dBu or Hi Gain (+19 dBu) as reference level. This unusual feature offers two advantages. First, the reference level can be easily switched to match any of RME's current interface devices, from HDSP 9632 through Multiface up to the renowned ADI-8 series converters. Second, the Signal to Noise ratio is optimized, and the Clip-LED will exactly match the ones of the ADI-8 (2 dB below 0 dBFS).

The balanced line level output signal is available at the back of the unit via 8 stereo TRS jacks. The specially developed, internal hi-performance switch mode power supply lets the OctaMic II operate in the range of 100V to 240V AC. It is short-circuit-proof, has an integrated line-filter, is fully regulated against voltage fluctuations, and suppresses mains interference.

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AD-Conversion

The 8-Channel AD-conversion of the OctaMic II operates at up to 192 kHz. The digitized signal is available simultaneously at the double ADAT output (S/MUX, up to 96 kHz), and at a DB-25 connector (4 AES/EBU outputs, up to 192 kHz). The digital part can be clocked internally (master) and externally via word clock, AES/EBU and SPDIF.

RME's outstanding SteadyClock(TM) ensures perfect AD-conversion, as jitter on the external sync-sources is nearly completely removed. All settings are done via DIP-switches on the back of the OctaMic II. Analog outputs and both digital outputs operate fully simultaneously. The choice of reference level affects the analog outputs only, the signal/clip indication and the AD-conversion will react only to the Gain-pots.


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Tech Specs

8 balanced XLR/TRS mic/line inputs

54 dB gain range

Input impedance: XLR 2 kOhm, TRS 5 kOhm

Analog input level: from -40 dBu up to +21 dBu

Maximum output level: +21 dBu

Output impedance: 75 Ohm

Output level switchable Hi Gain / +4 dBu / -10 dBV

Signal to noise ratio (SNR): 129 dB EIN @ 150 Ohm

THD:
Large frequency range (200 kHz) with special EMI input filtering

Frequency response -0.5 dB: 5 Hz - 200 kHz

Hi-pass filter: 80 Hz, 18 dB/oct.

Line Out: 1/4" TRS (6.3 mm stereo jack), servo-balanced

Phantom power: +48 Volt switchable per channel

Internal wide range switching power supply 100-240 Volt AC

Unbeatable price/performance ratio!

AD conversion

SNR: >110 dB(A)

Supported sample rates: 28 kHz - 200 kHz

THD:
Sync Sources: AES/EBU (also SPDIF coaxial), wordclock, internal

SteadyClock(TM) ensures best sound quality even with jittery external clocks


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Accessories

Digital breakout cable Pro, AES/EBU, D-sub25 to 4x XLR-3 female + 4x XLR-3 male, 1m/3m/6m (ALVA Audio)
Digital D-sub cable, AES/EBU, D-sub25 male to D-Sub25 male, 1m/3m/6m (ALVA Audio)
Optical ADAT Toslink cable 1m/2m/3m/5m/10m (ALVA Audio)
Word Clock cable, 1 x BNC male to 1 x BNC male, 1m/5m/10m (ALVA Audio)

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Add-On

BOB-32    Universal Breakout Box with 2 x 8 XLR to 2 D-sub connectors (supports TASCAM and YAMAHA format), flip-frame case

Applications

Console input extending for both Digital and Analog mixing
consoles in Studio, Live and Broadcast
Mic Pre-amps for ADAT/ Hard Disk/ Multitrack Recording
 
Innovation
If you love your compact Digital (or Analog) mixing console, but wish it had
more microphone inputs, ARX has the solution ? the 8 Pre: eight channels
of superb sounding Microphone Pre-amps in a compact 1 RU chassis.
The 8 Pre is the ideal console extender for those times when you need more
microphone inputs. Now you can put those unused line inputs to good use,
and who knows - the 8 Pre pre-amps sound so good that you?ll probably end
up using them all the time instead of the ones that came with your mixer!
Superb Audio Quality
The 8 Pre?s ultra low noise figures come from extensive use of premium
components plus care and attention to board design and layout. The result is
superb, transparent audio quality and the headroom to handle anything that a
mic can throw at it.
Gain is adjustable from 20 db through to 60 dB via a trim control on the front
panel, plus we?ve included a ?20dB Pad switch to tame the hottest condenser
mic output if required. The Clip status LED lights up 1 dB before the onset of
clipping, just to warn you you?re getting close.Phantom power is switchable in
banks of four channels: 1 through 4, 5 through 8. A Phase reverse switch is also
provided on each pre-amp channel to eliminate any close miking problems.
In short, the ARX 8 Pre is the mic Pre-amp that you?ll wish the console manufacturer
had used. It provides a unique solution to today?s multiple Mic Pre-amp requirements.

T E C H N I C A L S P E C I F I C A T I O N S
Input Gain 20dB to 60dB
Input Pad ?20dB
Input Impedance 4 KOhm
Input Headroom +23dB
Output Impedance 300 Ohm
Output Level (Max) +23dB
Frequency Response 20Hz ? 20KHz ±0.2 dB
Signal to Noise ratio (Gain set @ 20 dB)
?93dB Unweighted, ?99dB ?A? weighted
Distortion @ Unity Gain .004%, 20 Hz ? 10 KHz
Dynamic Range 116 dB
Phantom Power 48 VDC
Input Connectors Balanced XLR
Output Connectors Balanced TRS jack
Clip Indicator Illuminates 1 dB prior to clipping
Power Requirements 100/120 V AC, 220/240 V AC
Weight 5 lbs/2.2 Kg
Dimensions 19“W x 1?“H x 6“D, 482 x 44 x 155mm