VU Meter Test Signals

The signal files

VU meter test procedure

To use these signals, download the two wave files. Arrange to play the signal while connected to the VU meter being tested. You must take steps to ensure that the meter is driven from the conrect source impedance. From a 600-ohm line, this requires a 3600-ohm resistor in series with the meter. When driven from a zero-impedance source, this requires a 3900-ohm resistor. The source impedance seen by the meter affects the ballistics.

Play the 0VU signal, and adjust the level being sent to the meter for 0VU indication.

Now play the test signal, without changing any settings. The test signal is a tone burst, see below for specifications. A meter that fulfills the specification for a standard Volume Unit Indicator (aka VU meter) should indicate 95% of 0VU during the burst (on) period and 5% of 0VU during the silence (off).

Further discussion

The VU meter test signal gives you a qualitative way of assessing the impulse response of a meter having a scale marked in VU. Although there are many such meters made, only a select few can actually call themselves Volume Unit Indicators (i.e. VU meters).

The test signal is a tone burst, 1000Hz sine wave @ -12dB, 300ms on time, 300ms off time, derived from IEC Draft Publication 268, "Sound System Equipment, Standard Volume Indicators (1988) which measures response and return time of the movement. Consult the IEC document for the full specification.

A meter that fulfills the specification for a standard Volume Unit Indicator should indicate 95% of 0VU during the burst period and 5% of 0VU during silence. Use the 0VU wave file to set the 0VU indication on the test subject. You should note that a standard VU meter's impulse response depends on the source impedance it is driven from.

When driven from a 600-ohm line, a 3600-ohm series resistor in series with the meter is required. When driven from a zero-impedance source, like an opamp, the correct resistor value is 3900-ohms.

Last modified 2/4/2021.