If R2 is 100k does that make C1 1.6uf ?You want the center tap to be at AC ground. So the corner frequency of the C1 x R2 = 1/(2PiC1R2) should be low, say 1hz. A value of R2 = 10kohms and a 1hz corner frequency would make C1 = 16uf. Larger values of C1 would be fine. A larger value of R2 would let you get away with a smaller capacitor.