[Richard Crowley]

"W.G.D." wrote ...
I have a respectable but old(er) 'stereo' receiver, a Sony STR-V55
(along with a Sony PS-X75 turntable) which I use in a home-office.
L-R speakers are in-ceiling mtd.(!) Sound is fine; however, I would
like to pump-up the low end by adding a subwoofer. Rcvr and turntable
can support it; ceiling-mtd spkrs are OK at best. There is a set of
pre-amp out-in jumpers at the STR-V55's rear. What is the most
economical way to derive a "center-like" 'bass' channel from both L &
R channels?

Replace the "jumpers" with a pair of RCA "Y-adapters"
to maintain the loop connection. I would use the kind
with two male connectors and one female.

Run the L/R line-level signals to a powered sub-woofer
which has line-level inputs.