I tired to measure the frequency of the OT equalizer a looong time ago. Im not sure if my measurements are really reliable some values seems strange to me 
Anyway here is what I found (left column = equalizer value, right = frequency in Hertz) :
6 8.075
10 10.7666
12 10.7666
14 13.4583
16 16.1499
22 21.5332
26 26.9165
28 32.2998
30 34.9915
32 40.3748
34 45.7581
36 51.1414
38 59.2163
40 67.2913
42 80.7495
44 86.1328
46 104.9744
48 118.4326
50 131.8909
52 156.1157
54 166.8823
56 196.4905
58 226.0986
60 247.6318
62 290.6982
64 336.4563
66 387.5977
68 427.9724
70 495.2637
72 565.2466
74 645.9961
76 726.7456
78 820.9534
80 944.7693
82 1087.4268
84 1246.2341
86 1426.5747
88 1579.9988
90 1833.0139
92 2088.7207
94 2339.0442
96 2723.9502
98 3095.3979
100 3520.6787
102 4059.0088
104 4519.281
106 5170.6604
108 5924.3225
110 6788.3423
112 7633.5205
114 8809.7717
116 10039.856
118 11417.981
120 13116.4124
122 14849.8352
124 16938.5559
126 19188.7756