Secondhand Aphex Dual Channel Audio Expander / Gate - Part # 612Used Aphex Dual Channel Expander Noise Gate Audio Processor. Item No. 612. Preloved Aphex expander noise gate unit. This item was used by myself for approximately 3 months for a band that I accepted a mixing job with but subsequently split up. Description: Two Channel Stereo expander gate. A true dual channel expander using downward expansion with a variable ratio (1. 2: 1 to 30: 1), thus allowing an infinite variety of dynamics control which are