Red Evolution Mic Pre: Air Mode

Emulating The Classic ISA Sound In Today’s Flagship Interfaces

Air is the name we give to the sonic signature of our classic transformer-based ISA Preamp, which first appeared in the ISA 110 modules designed by Rupert Neve for Sir George Martin at Air Monserrat Studios. Though 'Air' it has deep historical associations with the origins of Focusrite, our customers coined the term as a simple description of the effect added by the ISA preamp to their recordings. The audible Air we refer to is the result of several attributes of the complex analogue ISA 110 circuit. Central to this design is a Lundahl LL1538 transformer — one on every channel — which is a hardware component that imparts a huge amount of sonic character.

  • ISA 110 modules

The most significant sonic attributes of the transformer-based ISA design are the impedance interaction between input stage and microphone, the low distortion and high linearity of the preamp design, and the frequency response tilt: an emphasis in the high end of the audio spectrum created by the resonance of the Lundahl transformer. The result, put simply, is an emphasis on the high end that's more than just an EQ lift. Vocals become flighty and vibrant; percussion, guitars and other acoustic sources become etherial and nuanced. Mixes are clearer and more emotive. Music comes alive.

Air Mode On Red Evolution Mic Pres

Because the Red Evolution mic pre is a transformerless design the Air character has to be applied using alternative methods. Engaging Air on the Red Evolution mic pre switches the input impedance from a nominal value of 6.2k Ohms to the lower figure of 2.2k Ohms to change the interaction between the microphone and the preamp. Simultaneously, a simple analogue circuit is engaged, which accurately recreates the high-frequency response of the ISA preamp circuitry using a specifically designed filter curve. The combined result is more presence and clarity: Air.

  • Diagram of Air frequency response on Red Evolution mic pres

Feedback from professional engineers is that Air is a phenomenally useful tool when recording. For James Towler, house engineer at Steve Winwood's Wincraft Studios complex, Red Evolution mic pres provide outstanding sonic performance on top of the phenomenal power and routing potential of his Red 8Pre. [The Red Evolution mic pres] “give me the focus and clarity that I'm looking for in my mixes," he explains. “Musicians have commented on the clarity in their ears. Steve [Winwood] plays organ bass, which used to sound wobbly and wavy before we had the Red 8Pre. Now it sounds solid — it's a lovely sonic flavour which I like."

  • James Towler, house engineer at Wincraft Studios

The Red Evolution microphone preamp features on the Red 4Pre, Red 8Pre and Red 16Line interfaces, in addition to the RedNet X2P. Air mode is independently switchable on each preamp using RedNet Control. On Red interfaces, Air mode is switchable from the front panel via the Config menu. On X2P, each of the two channels has a dedicated Air button.