is correct to use the spectral analyser function of DIGIcheck to detect the background noise in a channel ? If Y monitor the channel without playng it Y detect the presence of a frequence till -80 to -70 dB uniformly on all frequencies (25 --> 20k); but if Y pull off the power cord using the cells every frequence disappear while if Y play the channell appear the spectrum shape, centered around 6- 800 Hz tipical of instrument (a flute). Is correct to interpret this as the presence of background noise coming from power outllet ? Thanks niky