Steve, if you have time, place a 135 ohm 5 watt wirewound resistor in front of
each 1N4007 diode string.
If you have more time use a reversed 9.1v 5watt zener diode in the center tap to
ground too.
I think that will smooth out that SS recitifier sound a bit and give you a little more of that hollowstate feel. 
Bruce