Panasonic VP-7782A Audio Analyzer

I VP-7782A :

The VP-7721A measures levels in true RMS from 100 Volts (+40 dBV) down to 100 microvolts (-90 dBV) full scale.

Signal-to-noise ratio is automated by measuring and holding the signal level on one meter, then the generator automatically mutes after 1.5 seconds and the second autoranging meter measures the remaining noise. The difference between the two readings is the signal-to-noise ratio.

THD + Noise is measured to 0.003% (-90 dB) full scale. It’s marked “THD,” but it’s really measuring THD + Noise. It notches the fundamental and measures what’s left in true RMS with a 700 kHz bandwidth.

THD measurements are automatically tuned to the generator’s setting, and the reference level is automatically set to the measured input level, even as the input level varies.

Since the analyzer auto-tunes to the generator internally, if you use an external generator or test signal, tune the generator to the same frequency as the test signal to tune the distortion analyzer. Adjust the frequency slightly if needed for the lowest distortion reading; if I’m within a couple of percent of frequency I’m fine.

400 Hz high-pass and 30 kHz and 80 kHz low-pass filters each have their own buttons. The weighting button is for optional filters.