Behringer SHARK FBQ100 Automatic Feedback Destroyer - $60 (Bellingham)

Works excellent.
The SHARK FBQ100 also has an integrated mic preamplifier with 48V phantom power for use with condenser mics.
The balanced XLR and 1/4" inputs can accept mic and line signals with full gain control.
There are also balanced XLR and 1/4" outputs for wide system compatibility.
A delay line offers up to 2.
5 seconds of adjustable delay, while a noise gate offers automatic and manual parameter settings.
There is an automatic compressor with variable density, as well as a subsonic filter with an adjustable cut-off frequency.
Compact design, ideal for PA applications The intelligent "learn mode" can automatically equalize your PA and protect your system from feedback The search algorithm uses narrow 1/60 octave single-shot FBQ filters that can destroy up to 8 feedback frequencies while maintaining sonic integrity.
The remaining filters work automatically as required, adjusting only feedback-specific frequencies The adjustable mic preamplifier has ultra-low noise technology for high-quality sound.
It also offers 48V phantom power for use with condenser mics The balanced gold-plated XLR and 1/4" inputs can accept mic and line signals with full gain control Servo-balanced gold-plated XLR and 1/4" outputs let you choose between line or mic output levels for connecting and converting virtually any type of signal with a variety of devices The delay line offers up to 2.
5 seconds of delay, which can be adjusted in meters, feet, or milliseconds to compensate for time variations due to speaker positioning in large venues The noise gate offers automatic and manual parameter settings There is an automatic compressor with variable density Integrated subsonic filter with an adjustable cut-off frequency Optional rack-mount kit available (sold separately) for convenient installation