Really nice switched capacitor audio filter, from 2440 down to 100hz. Needs 12vdc. A 10 operational, a 9 cosmetically (small scratches).
Filter would be nice addition to older rig with limited filtering.
I don't have manual, but really simple to operate. Built in nice metal case, has wired 1/4" plug to connect to receiver......just supply headphones or amp speaker and you're in business.
$30 shipped to lower 48. PayPal, MO, check....etc....
Ed, send email to firstname.lastname@example.org