Our Heritage Sound

Focusrite grew out of a 1985 request from Sir George Martin to legendary recording console designer Rupert Neve to build a no-compromise mic pre and EQ for the console at Air Studios Montserrat. The resulting modules, prefixed with the letters ISA (Input Signal Amplifier), featured a transformer-coupled mic preamplifier, sophisticated EQ and a truly musical compressor design. Found first in the Forte console and subsequently the Studio console, ISA modules were the epitome of audio clarity, and were later sold as outboard units, where they rapidly became renowned for their no-compromise sound.

  • Sir George Martin holding an ISA preamp
  • Focusrite Studio Console

The Focusrite Studio Console

After Phil Dudderidge became the owner of Focusrite in 1989, he went about taking the phenomenal Forte console and re-designing it with a more studio-friendly topology and layout. While they were highly sought after by producers and engineers, only ten were made; most are still in use today. In 2014, we made a film about the Studio Console, which you can watch below.

"The ISA preamp sounds great on anything that has high transients and I love the Focusrite EQ; it is so efficient"
Rafa Sardina - Producer, Mixer, Engineer - Lady Gaga, Beyoncé, Celine Dion, Stevie Wonder, Michael Jackson, Elvis Costello and the Roots

  • Focusrite legacy rackmount modules

Rackmount Modules

While the Forte and Studio consoles remained rarities, the mic pres, EQ and dynamics modules that made them so desirable became very common. Units from the distinctive Red Range, launched in 1993 to worldwide acclaim, were in demand because of their unique warmth and character, and found themselves in studios of all sizes around the world. The Focusrite Blue Range also borrowed ISA circuit topology, and commands attention on second-hand markets nearly 30 years later. These designs, virtually unchanged today, lie at the heart of the ISA Range, and preserve the Focusrite Heritage Sound.

The Lundahl Story

Central to the ISA preamp design is the Lundahl LL1538 transformer — the same component that has been used in all Focusrite ISA preamps for decades — which gets the best out of any microphone, and provides a clean and open sound favoured by producers and engineers looking for unrivalled sound quality. Discover the Lundahl story below.

"Just as I liked the original, I like the Focusrite 428 MkII a lot. It features the same Lundahl transformers, is easy to use, sounds great, and delivers the goods as advertised"
Pro Sound Network

  • ISA 828MkII product image

The Dante Advantage

Focusrite's commitment to designing great-sounding equipment for audio professionals continues with the RedNet range of Audio-Over-IP devices and the Red range of audio interfaces. As an early champion of Audinate's Dante platform, Focusrite were among the first studio audio companies who paved the way for professional audio equipment in the Audio-Over-IP space. Bringing the heritage sound into the future, the ADN Dante-enabled option cards for the ISA range enables the ISA One, ISA 428 MkII and ISA 828 MkII to operate on Dante networks. Now, the classic ISA preamp, which placed Focusrite on the audio map in the 1980s, can be the front-end to any Dante audio system.


Featuring a rugged, portable all-metal enclosure, ISA One combines the classic Focusrite microphone preamp with a flexible, independent DI channel and optional 192kHz precision A-D conversion. At the heart of the ISA range is the microphone preamplifier with its Lundahl input transformer – essentially the same circuit, based on the original ISA 110, that has been used for 30 years in successive Focusrite designs.

ISA 428 MkII

ISA 428 MkII incorporates four of Focusrite's renowned mic pres in a simple-to-operate 2U enclosure, placing four mic preamps, instrument inputs and line ins at your fingertips. The original Focusrite mic pre was designed to suit the microphones of the time; today's model makes one small change, adding three additional input impedances to the classic ISA 110 setting.


The ISA 828MkII incorporates eight of Focusrite's classic mic preamps, with Lundahl LL1538 transformers on every input. Each channel has the option of mic or line inputs,while inputs 1-4 also feature instrument inputs on the front panel. Each mic pre has variable input impedance, to provide a range of subtly different sonic options when using microphones, including an 'ISA 110' setting, which replicates the impedance of the original Focusrite mic pre.


ISA ADN2 is an optional two-channel A-D card that provides high-quality analogue-to-digital conversion for the ISA One mic preamp and DI. Featuring Dante, AES3, ADAT andS/PDIF connectivity, the card operates at sample rates up to 24-bit/192kHz.


ISA ADN8 is an optional eight-channel A-D card that provides high-quality analogue-to-digital conversion for the Focusrite ISA 428 MkII and ISA 828 MkII microphone preamps. Featuring Dante, AES3 and ADAT connectivity, the card operates at sample rates up to 24-bit / 192kHz.