Focusrite’s new ISA828 eight-channel microphone preamp might be viewed as the ‘grown-up’ equivalent of the Focusrite Octopre and, indeed, it could be used as exactly that. However, it is far more versatile and more highly specified than its Platinum pal, incorporating eight ISA transformer-based preamps, with circuitry based on the original Rupert Neve design used in the well-regarded Forte console, and subsequently in the ISA430 Mk2 and ISA428 preamps.
On the input stage, this circuit still uses the same high-spec Lundahl L1538 audio transformer and Rupert Neve’s Zobel filter network. The aforementioned type of network is more usually associated with the speaker outputs of power amplifiers, to compensate for the inductive load of the speakers, but here it compensates for the inductance of the input transformer. All this fits into a mains-powered, 2U chassis.
Even discounting the optional digital capabilities included with the review model, the ISA828 provides the most cost-effective ‘per channel’ means of buying this particular design of preamplifier.