freq - frequency in Hz
Vcc - power supply voltage, professional power supply is used.
 
Audio amplifier TDK2040 is tested. 

Double cascade is used with 8 diodes BY6 and 8 capacitors, per side (16 diodes and 16 capacitors are used in the total). 

ETD49 core with 12 isolated layers as secondary, 300um gap and 4-turn primary.

Vcc = 12V
  f[kHz] | V[kV]
 --------|--------
     1   |   3.8
     2   |   4.5
     3   |   4.5
     4   |   5.1
     5   |   4.4
     6   |   4.4
     7   |   5.0
     8   |   6.0
     9   |   7.9
    10   |  10.6
    11   |  13.8
    12   |  17.1
    13   |  20.2
    14   |  22.0
    15   |  20.2
    16   |  17.7
    17   |  13.3
    18   |  11.0
    19   |   9.7
    20   |   8.9	
	
Vcc = 15V
  f[kHz] | V[kV]
 --------|--------
     1   |   4.4
     2   |   4.6
     3   |   4.7
     4   |   5.0
     5   |   4.4
     6   |   4.4
     7   |   5.0
     8   |   6.1
     9   |   7.6
    10   |  10.6
    11   |  13.7
    12   |  16.8
    13   |  19.1
    14   |  23.0
    15   |  22.1
    16   |  18.4
    17   |  14.5
    18   |  11.3
    19   |  10.3
    20   |   9.2