Focusrite ISA 828 8-Channel Mic Preamp

The Focusrite ISA828 eight channel microphone pre-amplifier, providing 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, with switchable impedance and direct instrument inputs, are complemented by eight line inputs, eight line outputs and an optional eight-channel 192kHz ADC.  Thanks to its convenient 25-pin D-Type connectors, the ISA828 integrates quickly and seamlessly with ProTools HD, as well as other popular hard disc recorders and mixing desks.

The microphone input stage includes a variable impedance circuit, allowing the user 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, 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 points are also featured on every channel, should the need arise to place extra processing between the pre amp and converter, Vintage design high pass filters are also provided on every channel, ideal for eliminating unwanted low frequencies without affecting the rest of the audio signal.   The ISA 828's new optional eight-channel 192kHz ADC is the first audio ADC to utilise 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.

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.

Mic Input Response

• Gain range: 0dB to 60dB in 10dB steps
•  Input Impedance, variable: 600?, 1k4?, 2k4?, 6k8?
• 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: 10k? 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: 1M? or 300k?
• 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

• 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)