Audio mV meter
This is a reliable audio millivoltmeter with a very linear and precise indication of audiolevels, i use my own meter all the time!
The only IC used is a FET-input CA3140, the frequency response is more than the audiorange 20Hz to 20kHz, more like up to 30-35kHz without decrease of sensitivity, the ranges is 15mV, 50mV, 150mV, 500mV 1,5V and 5Volt.
Added is the possibility to measure a terminated signal, at the termination selector switch you will have 600 ohm, 10k, 22k, 47k, 100k, 220k and 470k, just like the inputs of ordinary amplifiers.
Schematic (.pdf)
PCB (.pdf)
Placement (.pdf)
Except for the PCB and the components you will also need to add a 100ľA meter and a powersupply using two 9V batteries.
