Using single CT supply with LM3886

[TDWesty]

I have built a stereo LM3886 amp using a single PSU board and dual amp boards from chipamp.com. Because I am new to this, I am using an old 25V CT transformer I had on hand, not a dual secondary type as recommended for the PSU board, so mine has only 3 wires on secondary - 2 AC + the CT. I found a reference for an older PSU board for the LM3875 on how to use this type of transformer, but am not sure if I have done this correctly. Where does the CT connect ideally? Does it matter? I am trying with no success to eliminate hum, and moving the CT around has no effect (even leaving it off completely), so I am now wondering if my use of a single secondary supply is part of the problem.

I do get a steady and even 37VDC on each rail, and the amp does sound fine, aside from the hum, which is ok with no source connected, but with a source, or a loose RCA cable, hum becomes fairly intrusive.
I've tried without much success to find any schematics showing this type of TF used.