Hello, I have passive pickups, and have installed an EMG active preamp on a push/pull knob into my guitar (EMG AB After Burner). Will my guitar signal be low impedance regardless of whether or not the preamp is engaged?
Depends on what you mean by 'low impedance.'
I mean, most normal passives are in the 7-10kO range.

Anyway, when you disengage the boost it -should- be bypassed in a manner which makes your guitar electrically identical to if the boost were not installed, or very near to it.
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