The High/Low Shelf is an original design, transistor-based EQ and Boost circuit. The Low control boosts everything below 900Hz, the High controls everything above. Both Frequency bands boost/cut 16dB. Volume output can boost up to 20dB.
This circuit works as all of the following: Treble booster, bass booster, volume booster, articulation tightener, brightness reducer, etc.
True bypass, 15mA current draw, 9-18Volt operation