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RCA / Cinch Y-adapter (stereo to mono downmix for subwoofer) by jk_printer | Download free STL model | Printables.com
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Monoprice Audio/stereo Cable - 0.5 Feet - Black | Rca Plug/2 Rca Jack, Mono Source To Stereo System : Target
3.5mm Stereo Male to Mono RCA Stereo Male Adapter Cable - Micro Connectors, Inc.
Amazon.com: SPRODIO Single Stereo to Mono Converter, RCA L/R Audio Adapter Stereo to Mono summing Cable Adapter SC21 : Musical Instruments
Rolls DB226 Stereo Line to Balanced Mono Converter DB226 B&H
0.5ft (0.15m) Value Series™ One RCA Mono Male to Two RCA Stereo Male Y-Cable | Audio Adapters and Couplers | Adapters and Couplers | Audio Video
6 RCA Mono to Stereo Cable RCA F to Dual RCA Males | Computer Cable Store
Offex 1/4 inch Mono Phono to Dual RCA adapter, 1/4 Mono Male to Dual RCA Female, 6 inch - Walmart.com
Earphone Audio Jack 3.5mm Connector Stereo Adapter Male Female RCA Audio Mono Channel Plug to Screw Terminal Mono Channel Plug - AliExpress