FOCUSRITE ISA 428 MKII FOUR CHANNELS MIC PREAMPLIFIER

Mic Inputs
• Frequency response at minimum gain (0dB): -0.35dB at 20Hz and –3dB at 122kHz
• Frequency response at maximum gain (60dB): –2.5dB at 20Hz and –3dB 103kHz
• Gain range: 0dB to +60dB in 10dB steps, plus 0dB to +20dB continuously variable trim
• Maximum headroom: +7.4dBu
• THD+N: 0.0009% (measured at 1kHz -20dBu input signal, at 30dB gain setting, with a 20Hz/22kHz bandpass filter)
• Noise EIN: -126dB (measured at 60dB of gain with 150Ω termination and 20Hz/22kHz bandpass filter)
• Noise at main output with unity gain: -98dBu (measured with a 20Hz/22kHz bandpass filter)
• SNR: 123dB (relative to max output 25dBu)
• SNR: 120dB (relative to 0dBFS (+22dBu)
• CMRR: 88dB.
• Input Impedance, variable: 600Ω, 1400Ω, 2400Ω, 6800Ω

Line Inputs
• Frequency Response at unity gain (0dB): -0.3dB at 20Hz and –3dB at 94kHz
• Gain range: -20dB to +10dB in 10dB steps, plus 0dB to +20dB continuously variable trim
• Maximum headroom: +25.4dBu
• THD+N: 0.002% (measured with +4dBu input signal, 0dB gain setting, with a 20Hz/22kHz bandpass filter)
• Noise at main output with unity gain: -91dBu (measured with a 20Hz/22kHz bandpass filter)
• SNR: 116dB (relative to max output 25dBu)
• SNR: 113dB (relative to 0dBFS +22dBu). Input Impedance: 10kΩ

Instrument Inputs
• Frequency Response at +10dB gain: -0.2dB at 20Hz and 0dB at 200kHz
• Frequency Response at +40dB gain: -3dB at 20Hz and –3dB at 38.4kHz
• Gain range: +10dB to +40dB continuously variable
• Maximum headroom: +11.5dBu
• THD+N: 0.006% (measured with –20dBu input signal, at minimum gain (+10dB), with a 20Hz/22kHz bandpass filter)
• Noise at main output with minimum gain (+10dB): -95dBu (measured with a 20Hz/22kHz bandpass filter)
• Input Impedance = >1MΩ

High Pass Filter
• Roll off = 18dB per octave 3 pole filter
• Frequency range: 16Hz to 420Hz (continuously variable, measured at the 3dB down point)

Meters
• 6 LED meter is calibrated 0dBFS = +22dBu (the maximum level which can be correctly converted by the optional internal A/D converter before overload occurs). The meter calibration points are as follows:

Meter panel calibration value in dBFS / Equivalent dBu value
0dBFS / +22dBu
-2dBFS / +20dBu
-6dBFS / +16dBu
-12dBFS / +10dBu
-18dBFS / +4dBu
-42dBFS / -20dBu



Front and rear connectivity

Analogue Channel Inputs (Inputs 1-4)
• 4 instrument 1⁄4” TS jack inputs on front panel
• 4 microphone XLR inputs on rear panel
• 4 line 1⁄4” TRS jacks on rear panel
• 4 insert return 1⁄4” TRS jacks on rear panel
• 4 ADC XLR inputs on rear panel

Analogue Audio Outputs (Outputs 1-4)
• 4 line XLR outputs on rear panel
• 4 insert send 1⁄4” TRS jacks on rear panel

Other I/O
• IEC power input connector 100Vac – 240Vac

Front Panel Indicators
• 8 output meters, 6 segment
• 4 30-60 mic gain range selection indicator
• 4 +48V phantom power indicator
• 4 Phase indicator
• 4 Insert In indicator
• 4 Filter In indicator
• 4 Input selection indicators (Mic, Line, Inst)
• 4 Z In microphone input impedance selection indicators (Low, ISA110, Med, High) Clock select indicators (44.1, 48, 88.2, 96, 176.4, 192)
• Ext clock indicators (Lock, Word clock, 256X)

Weight
5.5kg
12.2lbs

Dimensions (W x H x D)
480mm (W) x 88mm (H) x 280mm (D)
19" (W) x 3.5" (H) x 11" (D)

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.

• • Ultra-high quality 8-channel A/D and D/A interface for virtually any digital recording/mixing environment
  • 8 state-of-the-art MIDAS designed Mic Preamplifiers
  • Phantom power on all microphone inputs
  • Reference-class Cirrus Logic 24-bit converters for ultimate signal integrity
  • Processes 48 and 44.1 kHz sample rates
  • External sample rate synchronization via word clock or ADAT input

• Optical ADAT in/out interface for ultimate compatibility
• All mic/line inputs routed to the ADAT output
• ADAT input routed to all Line outputs
• “Planet Earth" switching power supply for maximum flexibility (100 - 240 V~), noise-free audio, superior transient response plus low power consumption for energy saving
• High-quality components and exceptionally rugged construction ensure long life
• Conceived and designed by BEHRINGER Germany

 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.

Top
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.


Top
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


Top
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)

Top
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

• Maximum of 66 dB of gain, in eleven discrete steps
• Dynamic range exceeding 120 dB
• 10 Hz to 50 kHz audio bandwidth
• High immunity to RF interference
• High current line output driver
• Transformer-balanced input and output
• Extended range peak limiter via dual opto-isolators makes preamplifier virtually "unclippable“
• Selectable 48-volt / 12-volt phantom power or 12-volt "T" power
• High-pass filter @ 80 or 160 Hz, 6 dB per octave
• Headphone monitoring of microphone audio, monitor audio, or a mix of both
• Monitor input accepts mono, balanced or unbalanced line-level inputs on 1/4-inch tip-ring-sleeve connector
• Separate level control of Monitor gain and overall headphone gain
• Split ear function via DIP switches
• Internal battery power (two-AA)
• Excellent battery life with alkaline and NiMH rechargeable batteries
• External 5-17 VDC powering (plug included)
• High-strength aluminum chassis with durable belt clip

Having had great success with the PRE-73 preamp, we have received many requests for a version for the 500 eries rack format. We are therefore happy to present the PRE-573, expected to start shipping in late September.
 
The PRE-573 is a one width module that has the sound and the features that made the PRE-73 so successful and a few additional ones.
The circuit still uses the preamp and output section from the classic 1073-module, adapted to work in the api rack format. It has a total  gain range from -15 to +80 dB. The 10 - 70 dB range is handled by a turn switch  and there is a separate toggle switch to select an additional 5 or 10 dB gain. The input can be configured to accept line level signals by another switch, the gain is then lowered by about 25 dB and the input impedance increased to about 15 kohm.
 
The input impedance of the mic input mode can be switched between 1200 and 300 ohm. Phantom power and phase reverse is also selectable by front panel switches.
 
An added feature, using the same circuit as in the PRE-73 DLX, is the active DI-input with a high input impedance of about 1,5 Mohm. The output signal from the active DI circuit passes through the input transformer for some extra character.
The DI-input is very flexible since it can be changed to a purely passive one by a front panel switch. The DI input is then exactly the same as in the PRE-73 Mk2 where the signal is feed directly into the second gain stage, bypassing the transformer and with an input impedance of about 100 kohm.

These two DI-options makes it possible to get different tones from electric instruments and the passive DI input mode is more suited for injecting active units like sound modules. 
 
A new feature is the switchable AIR mode that  adds a small boost above 10 kHz that peaks at 2 dB at about 35 kHz.

A simple but effective signal and overload indicator is offered by a single LED that starts glowing red at about +4 dBu and then increases its intensity up to the maximum output level.
 
The PRE-573 has a dedicated insert connector at the back allowing it to interface with other GAP 500 modules. The insert can be activated by removing a jumper connector at the back of the module.
The second Golden Age Project module for the api 500 rack will be the EQ-573, expected to ship in November 2012. The EQ-573 consists of the inductor based high pass filter section  and the 3-band eq section from the classic 1073 module with some added frequencies. These two modules together will offer a fully fledged 1073-module in a compact format at a very low cost.
 
There is a second jumper at the back of the module that selects 600 ohm termination on the output. The standard mode is termination on, since it gives the flattest response when the PRE-573 is used with modern line inputs that typically has an input impedance of 10 kohm or more. The user can chose to remove the jumper and deactivate the termination resistor, this will increase the level above 10 kHz and create a peak in the response for an even more pronounced  "Air" effect.
The output is transformer balanced and fully floating and can drive a 600 ohm load up to level of about 28 dBu.