The eight ISA-series transformer-based microphone preamps feature the same classic microphone preamplifier design as the original ISA110 module from Focusrite's critically acclaimed Forté console (including the original Lundahl L1538 transformer and bespoke zobel network).
The preamps are complemented by eight line inputs, eight line outputs and an optional eight channel 192kHz A-D converter boasting a dynamic range of 122dB. 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 preamp with any microphone, thus maximising 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 preamp 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.
Finally, every channel features a six LED input meter, complete with global precise meter trim. Metering has been designed to utilise the same reference points as Digidesign¬ís Pro Tools 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 ¬ñ3dB down at 110kHz
Frequency response at maximum gain (60dB): ¬ñ3dB down at 16Hz and ¬ñ3dB 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 ¬ñ3dB 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
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)