SV Sound SX-ST, SX-VT user manual MIC / Line Input Module

4. MIC / LINE INPUT MODULE

Traditional professional mixing consoles are generally based on the same input structure. The signal from the microphone goes through a phase reversal switch and then to a pad to attenuate the signal before going to the first amplification stage. Some mixers even introduce a transformer before the first stage to simplify the circuits. Reducing the signal level before amplifying it increases noise. It also limits the range of input signal that can be accommodated before overload distortion occurs. Some consoles even add a LF Cut before the transformer to avoid saturating it in presence of low frequencies at high level, meanwhile this might be useful under certain conditions, like strong wind noise, this causes phase shifting.

For ages this type of circuit has been used for analogue recording and nowadays

The new SONOSAX SX-ST & SX-VT input stages do not reduce the microphone level before amplification. Instead we control the amount of amplification and therefore no additional noise is introduced by this method. Using transformer less circuitries avoids unnecessary phase shifting, eliminate the risk of transformer saturation at low frequencies, offers a much better slew rate and allows very wide bandwidth with a flat frequency response as required for SACD

With a careful design of the input amplifier stages and selecting only the best of today's available components, it is nowpossible to handle a significant increase in the input level before overload. Conventional input stages require the operator to do a delicate balancing act between the input gain control and the channel fader to prevent unexpected input overload or so much gain that the noise comes up. Thus, heretofore unattainable low noise input figures and high input headroom figures are a reality.

SX-ST / SX-SV User Manual page 11