Theta chroma 396 HDCD dac 6db bypass for redbook playback

Hello fellow members,
I wonder if anyone is familiar to the 6 db defeat of the Pacific Microsonics PMD-100 HDCD filter.I have a Theta Chroma 396 HDCD dac,it uses the BB 67P-K d/a chip, CXD1244 / PMD100 HDCD filter.According to Pacific Microsonic spec, this 6db cut is necessary to account for the allegedly greater dynamic range of HDCD playback vs normal CD playback.All tests and reviews report that the non HDCD version of the dac is sonically superior to the HDCD one for normal cd playback.They also suggest ,included Robert Harley of Stereophile,that there is a simple mod to defeat the digital domain attenuation.Could anyone help?Any photos or schematics would be much appreciated!
Thank you,