I was a Dynaco St-70 series II new onwer one month ago and listen so many previously played CD, I feel the bass not enough compare with my previous power amp. (melody Sp3 bypass version). After that I saw many related st-70ii forum and modified totally 7 nos. of caps (3x100uf 100v, 2x100uf 400v & 2x68uf 450v replaced by “100uf 450v”). The result is good! The speed & reactions, bass are improved but the bass still not enough “deep”. Until I saw your forum discussion the st-70ii added the limiting bandwidth filter to cut-off the 17hz & 23khz sound source. Do you know is it the bass not enough deep reason ? If this is true, can I modified the c22 & R33 values to increase the low frequency? Or jump pass the filter, directly form input jacks to after R33 circuit board ?