Modifying preamp power supply

My current preamp, which is actualy front stage of A75 is using +/- 30V regulated power supply. I was planning on building Aleph P preamp in a same chassis and use the current PS. Can I connect regulated -30V to ground and use +30V as a positive voltage supply achieving that way +60V. The ground of the +/- 30V supply is not connected. Any advantages/disadvantages to that setup? Thanks for any info.