L.R. Baggs M1A Active Soundhole Pickup...

The M1 is a patented humbucking pickup with a twist.
In a common stacked humbucker, the lower coil cancels
hum, but doesn’t contribute anything positive to the
sound. We unlock the lower coil with a carefully tuned
support that allows it to capture higher frequency resonances.
As the pickup moves with the guitar’s soundboard, a body
signal is created in the suspended coil that adds presence
and realism to your amplified sound.

The M1 Active’s plug-and-play design features a preamp with
audiophile circuitry for that pure acoustic sound we are known for.
The built-in electronics boosts the pickup’s output for a full and
direct signal to any acoustic amplifier or P.A. system, eliminating
the need for any external preamps. The M1 Active includes a volume
control and adjustable pole pieces for perfect balance and tone
between the strings.