No. The Hum Debugger does NOT just have two levels of noise gating. It uses a SPECIAL ADAPTER to sample the power and anything attached to it. Then it uses noise cancelling technology to eliminate the noise.
From their web page:
“Not a noise gate, and not a noise suppressor—but a real hum extractor.”
The NORMAL/STRONG switch controls whether only odd numbered harmonix are eliminated in low setting, or both odd and even harmonix in high setting. From the manual:
“NORMAL/STRONG TOGGLE SWITCH - Sets the amount of Hum Elimination. In NORMAL mode the Hum Debugger removes only the odd harmonics from the hum present in your signal. In STRONG mode the Hum Debugger removes both odd and even harmonics from your signal’s hum content.”
Also from the manual:
“WARNING: Use only the 7.5VAC/400mA AC adapter the Hum Debugger comes supplied with. Do not use any other AC adapters. Using other AC adapters, even those made by Electro-Harmonix, could cause harm to the unit, the adapter or your drummer. The Hum Debugger does not use batteries.”
The reason that you must use the AC adapter that comes with it is that the special adapter is part of the circuit that samples the power signal.
This is, in fact, exactly what you were proposing.