This simple schematic diagram shows how to build a circuit that will indicate peak audio response on an analogue meter, similar to a tape recorders meter.
This peak level reading audio meter circuit diagram will only work with a MOSFET type op-amp, bipolar types i.e. 741 and J-FET. The LF351 op-amps will not work in this circuit.
The circuit also has a slow decay time and fast response time to indicate peak of the meter readings. The 1N4148 diode provides half wave rectification of the input signal, the dc output being smoothed by the 22u capacitor.
The capacitor will charge to the peak value of the input waveform, and then discharge via the meter and 18k resistor.