Focusrite ISA One

The superbly retro Focusrite ISA One with its tasty Lundahl L1538 transformer and bespoke Zobel network (a type of filter section) is a portable Rupert Neve-designed microphone preamp/active DI in a portable package. It even handles headphone monitoring. A four-way switch selects three broad gain bands, and a Trim control provides fine tuning. There are four mic input impedance settings, which can be used to match the ISA One with any microphone to maximise level or creatively shape the sound.
Further switches provide 75Hz roll-off, Phase, and phantom power. The mic/line preamp and the DI channel are fully independent, so you can easily combine a mic and DI signal for recording acoustics, or plug a guitar into the DI channel and then mic up a vocal. The Amp output allows you to DI and run an amp simultaneously and there's a send/return for external EQ or compression.
The optional digital card provides ADAT and TOSLink S/PDIF optical outputs and AES/S/PDIF outputs. It can also interface with older digital equipment and there's Word Clock in and out via BNCs. ADAT sample frequencies are 44.1K, 48K, 88.2K and 96K, and AES/S/PDIF reach 192KHz.

Verdict
The ISA One doesn't have the larger-than-life quality of valves or even of Neve's earlier solid state designs. It's clean, pure and transparent, but with a subtle way of improving on ‘reality'.  Variable impedance and 80dB of gain allow you to interface with any microphone, including vintage ribbons, and the neutral but enhanced sound quality make this a top general-purpose preamp rather than just a device for special occasions.