QUAD 33 tape board attenuation question

I have a modified Quad 33 which I use with various sources - turntable through the disc adapter board set up for Shure V15 III, cd through Radio input with 6.8k series and 3.3k shunt resistors for (I believe) 10db attenuation, and DAC handling signal from computer through the Tape circuit. If I set the adapter to H the level is lower than cd, and on M it is slightly too high. Can I change resistors on the adapter board to adjust to the same level, and if so, can anyone point me at the right ones to save me the task of puzzling it out (I'm not very good...)
 
Thank you! I already have 6k8 series and 3k3 shunt on Radio 1 for cd input which seems to work well (it was recommended when I first modified the unit a very long time ago) I have just tried adding the same values to Radio 2 input for the DAC and it also seems to work ok, and Flac files played through the DAC come out at the same level as the signal from a turntable playing through the disc adapter (which is modified to be the ideal loading for a Shure V15 III) I can now keep the Tape input with the standard values in case I want to use a cassette deck with it occasionally.