Design Example: Vintage Mixing Console

A sound engineer at a music company faces a challenge. The output from their newly acquired studio's vintage mixing console is insufficient for modern recording equipment.

To resolve this, the engineer needs to design an audio pre-amplifier using an operational amplifier, to boost the signal level.

The pre-amplifier should amplify the audio signal by a factor of 10, have an input impedance above ten kilo-ohms to prevent console overloading, and cover the entire audio spectrum from 20Hz to 20kHz.

The op-amp model 741 is chosen because it can handle the required frequency range without significant gain loss.

The engineer uses the non-inverting operational amplifier configuration to meet the requirement of a gain of 10 and high input impedance.

The gain of a non-inverting amplifier equals one plus the ratio of the feedback resistor to the resistor connected to the inverting input.

To achieve a gain of 10, a 180-kilo-ohm feedback resistor and a 20-kilo-ohm input resistor are selected.

This design effectively boosts the console's output, enabling it to drive the digital recording equipment.