With 4uF the resonance about at 8Hz (if you increase the capacitance, the frequency shifting down).
If you decrease the parafeed 10k:600 transformer secondary load (for example from 100k to 600R) the resonance hump size decreasing, till completely disappears. At 660R secondary load the size of capacitance (in the 1..10uF range) almost uninteresting, but the "gain" lower than in case of larger size of load.
If you decrease the parafeed 10k:600 transformer secondary load (for example from 100k to 600R) the resonance hump size decreasing, till completely disappears. At 660R secondary load the size of capacitance (in the 1..10uF range) almost uninteresting, but the "gain" lower than in case of larger size of load.