The Focusrite ISA 110 Original Mono Mic-Pre & Equalizer is a limited-edition version of the famed single-channel ISA 110 EQ module. The original ISA 110/130 units were developed by Rupert Neve, who had been commissioned to supply 16 extra inputs for a Neve console at AIR Studios. These 1984-era ancillary input modules fitted vertically into a rackmounted card cage that required an external power supply. Around 1986, Focusrite began selling outboard racks containing two, four or eight ISA 110/130 modules, and in 1989 the module became the basis of the Focusrite Studio console (of which only ten were made). The Focusrite Red Range products and the ISA 215 units are also derived in part from the original 110 module.The new ISA 110 differs from the original in that it is packaged in a horizontal one-rackspace unit with an internal power supply. However, the electronic circuit design, the componentry and the performance specifications are all exactly the same as the original ISA 110. The original printed circuit board has been extended to include the integral power supply and accessible rear panel insert jacks, both new features.Popping the hood reveals why this preamplifier sounds and works the way it does. Focusrite has designed proprietary transformers specifically for the ISA 110, for both line and microphone level inputs. The mic input transformer and the high-capacity power supply transformer both use mu-metal shielding for maximum low-noise performance. All the rotary switches are U.S.-made gold-plated switches, the push buttons are Swiss-made, and all the pots are manufactured in France using conductive plastic for maximum accuracy and smooth feel. The equalizer’s shelving bands use rotary switches with individual capacitors for each frequency and one op amp for maximum fidelity and minimum distortion. Because rotary switches are much more expensive than pots, this qualifies as a costly “audiophile” design; switching individual capacitors are usually replaced by a cheaper single-capacitor circuit design and another pot.All circuit functions are switched in and out of circuit by way of relays featuring gold-plated silver levers sealed in inert gas containers (compared to FET switching, relays are best for preventing breakthrough and distortion). The main audio op amp used through out the ISA 110 is the 5534.