While I can't help with Bytor's DIY Y, I can at least link to a couple examples: the Outlaw PCA Y-adapter (which is ideally suited to your application -- connect it to the output and connect two standard analog audio cables from it to the BP2000's) or a couple examples from Radio Shack (neither of which has the same arrangement of connectors that would allow you to use them without some additional tinkering around).

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