Rather than creating a similar sound to vintage units, as with modelling devices, Liquid Technology samples their sonic behaviour. This is achieved through Dynamic Convolution; the application of a unique, level-dependent set of responses to an audio signal. These measured responses, sampled at numerous levels and with every possible setting combination, are applied to the input stream on a sample-by-sample basis for accurate emulation.
However, mic pre emulation can't be achieved with software alone. Hardware is required in addition to account for the physical interaction with the microphone. Mic pre's have always had to connect to the source microphone, but it's an interactive system that isn't 100% efficient. Microphone preamps have been designed since 1920's to suit a wide variety of different types of mics - passive carbon dynamics, then coil-based designs, then valve amplifiers, large diaphragms, phantom powered condensers etc. Hence, different vintages and types of mic preamp, will vary dramatically in terms of the way that their input has been designed. For example, the range of electronic/transformer front ends that have been used over the years exhibit a wide-ranging set of impedances, and this is why an analogue front end needs to be included. If a specific mic is not being loaded by the analogue circuit just as it was by an original vintage device, then the sound from that microphone will be different. The is no real mic pre standard. Take a transformer for instance. It has two coils of wire, the 1st coil generates a magnetic field, and this then passes into the 2nd coil, which in itself is not a fixed transfer mechanism. There's a lot of variation in transformers. What impedance appears at the input of the preamp is also a key factor: When you connect a mic it has an output impedance of its own, the two sides (mic and preamp) react, and frequency-related level can vary wildly as a result. Capacitances also interact as both mic and transformer have capacitances that vary, so HF roll off may occur for example, or you may get an HF peak (The famous Focusrite 'airiness' typified by the ISA range for example). Older mics designed for broadcast applications often roll off at e.g. 12kHz, since before 1970 few people cared about HF matters. (Designers used to just roll off at c12kHz to filter out problems above this threshold).
Consequently the only way to accommodate the full range of different designs is to allow huge flexibility in the resistance and capacitance parameters in a custom transformer designed specifically for that flexibility. By including a 'Liquid' preamp circuit containing a flexible signal path (transformer or electronic) and variable impedance value, The Liquid Channel can mimic that of the classic mic pre to ensure that the interaction with the microphone is close to the original. The transformer used is a brand new custom precision-wound FF 'Liquid' transformer, designed and built in the UK by Focusrite's R and D department to be extremely flexible; transparent or coloured as required. Hence, The Liquid Channel physically changes analogue circuitry as well as using dynamic convolution technology to create mic pre emulations. For electronic or tube mic preamps that do not include a transformer, the Liquid Channel's transformer is auto-switched out. Focusrite has built in the variations required to reproduce the vagaries of a range of electronic mic pres. The capacitance and resistance are then varied in the circuit, and Dynamic Convolution technology is used to emulate the full range of electronic preamps. Tube emulation is also covered 100% - this is taken care of by the Dynamic Convolution process. Whatever artefacts were present in a classic vintage tube piece are also present in The Liquid Channel. The sound of every opto, and every VCA compressor, every transformer and electronically balanced mic preamp (including tube pre's) can be emulated, because each device's response has been calculated.
* IMPORTANT INFORMATION: FOCUSRITE, the FF logo, LIQUID TECHNOLOGY, LIQUID CONTROL and the LIQUID logo are trademarks of Focusrite Audio Engineering Ltd. DYNAMIC CONVOLUTION is a trademark of Sintefex Ltd. All other product names, trademarks, or trade names are the names of their respective owners, which are in no way associated, connected nor affiliated with Focusrite or its LIQUID CHANNEL product and which have not endorsed Focusrite's LIQUID CHANNEL product. These other product names, trademarks, and trade names are used solely to identify and describe the third party products the sonic behaviour of which was studied for the LIQUID CHANNEL product, and to accurately describe the functionality of the LIQUID CHANNEL product. The LIQUID CHANNEL product is an independently engineered technology which utilises the patented process of Dynamic Convolution to actually measure examples of the sonic impact of original analogue products upon an audio stream, so as to electronically emulate the performance of the original product studied. The result of this process is subjective and may not be perceived by a user as producing the same effects as the original products studied.