FocusRite ISA828 Mic Preamp

The ISA828 eight channel microphone pre-amplifier provides eight original ISA transformer-based pre amps in a single robust 2U chassis, offering the Focusrite signature sound at its lowest cost per channel to date.

The eight ISA-series transformer-based microphone pre amps feature the same classic microphone pre-amplifier design as the original ISA110 module from Focusrite's critically acclaimed Forte console (including the original Lundahl L1538 transformer and bespoke zobel network).

The pre-amps are complemented by eight line inputs, eight line outputs and an optional eight channel 192kHz ADC boasting the widest dynamic range of any converter to date. Thanks to its convenient 25 pin D-Type connectors, the ISA828 also integrates quickly and seamlessly with ProTools HD, as well as other popular hard disc recorders and mixing desks.

The microphone input stage additionally includes a variable impedance circuit, allowing the user to switch between four carefully selected input impedance settings. The original ISA110 setting is supplemented by three further impedance settings to either perfectly match the pre-amp with any microphone, thus maximizing level, or to use different settings creatively to shape the sound of the microphone being used.

The four front panel instrument inputs also feature high and low impedance options to provide a comprehensive and accessible DI solution. Insert switches are also featured on every channel, should the need arise to place extra processing between the pre amp and converter. Vintage design 75 Hz / 18dB per octave high pass filters are also provided on every channel, ensuring unwanted low frequencies are effectively eliminated.

The FocusRite ISA828 AD Card is an optional eight-channel 192kHz Analog-Digital Conversion card designed for use with the FocusRite ISA828 Mic Preamp. The FocusRite ISA828 AD Card is the first audio ADC to utilize Texas Instruments Burr-Brown Pro Audio Amplifiers and Flagship Analog to Digital Converter PCM4220 chips. This cutting-edge technology is encompassed within Focusrite's own custom analogue circuitry to provide eight channels of unparalleled A/D conversion, delivering a dynamic range of 122dB and jitter at < 250 picoseconds.  The FocusRite ISA828 AD Card is sold separately.


Rear of the FocusRite ISA828 Mic Preamp with the FocusRite ISA828 AD Card installed

Finally, every channel features a six LED input meter, complete with precise meter trim. Metering has been designed to utilise the same reference points as Digidesign’s HD system and provides clear and accurate input metering independent of the DAW.

Key Features
-Eight ISA series transformer-based pre amps
-In a single robust 2U chassis, offering the classic Focusrite pre at its lowest cost-per-channel to date.
-New Optional Eight Channel 192kHz ADC
-Embodies cutting-edge conversion technology, incorporating Focusrite analogue circuitry to deliver the best A/D performance on the market, bar none
-Convenient 25 pin D-Type connectors
-The ISA828 integrates quickly and seamlessly with ProTools HD, as well as other popular hard disk recorders and mixing desks.
-Switchable Impedance
-Selectable per channel; choose one of four carefully selected input impedances, including the original ISA110 setting, to suit any microphone.
-Direct Instrument inputs
-Each instrument input features high and low impedance options to provide a comprehensive and accessible DI solution.
-Inserting available on every channel
-Allows external devices to be inserted between the pre amp and the ADC, using the 25-pin D-type cable.
-High pass filter, Phase reverse and Phantom power
-Each has a dedicated switch, independent on each channel.
-Six LED input meter
-Complete with precise meter trim - Designed to utilise the same reference points as Digidesign’s HD™

Specifications
Mic Input Response
• Gain range: 0dB to 60dB in 10dB steps
• Input Impedance, variable: 600Ω, 1k4Ω, 2k4Ω, 6k8Ω
• EIN (equivalent input noise): -126dB measured at 60dB of gain with 150 Ohm terminating impedance and 22Hz/22kHz bandpass filter
• Noise at main output with gain at unity (0dB): -97dBu measured with a 22Hz/22kHz bandpass filter
• Signal to noise ratio relative to max headroom (9dBu): 106dB
• THD at medium gain (30dB): 0.0008% measured with a 1kHz -20dBu input signal and with a 22Hz/22kHz bandpass filter
• Frequency response at minimum gain (0dB): -0.5dB down at 10Hz and –3dB down at 110kHz
• Frequency response at maximum gain (60dB): –3dB down at 16Hz and –3dB down 85kHz
• CMRR: 91.8dB (Channel 1, 1kHz, maxiumum gain)
• Crosstalk Channel to Channel: with 10dB@1kHz input to chA, chB output =102dBrA. With 10dB@10kHz input to chA, chB output = 84dBrA

Line Input Response
• Gain range: -20dB to +10dB in 10dB steps
• Input Impedance: 10kΩ from 10Hz to 200kHz
• Noise at main output with gain at unity (0dB): -96dBu measured with a 22Hz/22kHz bandpass filter
• Signal to noise ratio relative to max headroom (24dBu): 120dB
• Signal to noise ratio relative to 0dBFS(+22dBu): 118dB
• THD at unity gain (0dB): 0.001% measured with a 0dBu input signal and with a 22Hz/22kHz bandpass filter
• Frequency Response at unity gain (0dB): 0.3dB down at 10Hz and –3dB down at 122kHz

Instrument Input Response
• Gain range: 10dB to 40dB continuously variable
• Input Impedance: 1MΩ or 300kΩ
• Noise at minimum gain (+10dB): -90dBu measured with a 22Hz/22kHz bandpass filter
• Noise at maximum gain (+40dB): -62dBu measured with a 22Hz/22kHz bandpass filter
• THD at minimum gain (+10dB): 0.002% measured with a 10dBu input signal and with a 22Hz/22kHz bandpass filter
• Frequency Response at 10dB gain with -10dB input: 10Hz-200kHz +/- 0.6dB
• Frequency Response at 40dB gain with -40dB input: -2.5dB down at 10Hz and 0dB at 200kHz

High Pass Filter
• Roll off: 18dB per octave 3 pole filter
• Fixed Frequency 75Hz measured at the 3dB down point

Weight
• 8.84kg
• 19.5Ibs

Dimensions
• 484mm (W) x 85mm (H) x 305mm (D) (350mm depth with heat sink)
• 19" (W) x 3.5" (H) x 12" (D) (13.8" depth with heat sink)