How do i hookup a subwoofer to it?
Probably through either the headphone output or one of the RCA outputs on the rear.
This is the only discussion I could find to address your sub issue:
https://audiokarma.org/forums/index.php?threads/sansui-alpha-au607-output%E2%80%99s.877604/I currently run a 1973 Sansui 771 where I run a pair of Bose 501's off the receiver, the run the receiver into a Presonus monitor station where the sansui is added to a pair of Mackie HR824's powered speakers and also a set of JBL powered speakers with the Presonus getting its signal form a Samsung TV. The sound is amazing and the Bose to Sansui setup rounds off the low base very nicely.
Many powered subwoofers can accept speaker level inputs, in addition to RCA. If your sub has speaker wire connections on the back, then you need only run a second pair of speaker wires from the amplifier to the sub.
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