Hi Pos, hummm. 200KHZ , 150, 100 why and I really would rather audio trannies in my designs not reach that far. As is most seem to hit about 70K at only a minor drop from pass band.

I actually design into the amps a frequency limiting measure to prevent them form going past about 35K. IMO only noise and possible EMI out above that. When I order custom trannies (most of my projects have them) I specify flat pass band from 20HZ to 25KHZ with a smooth roll off one octave on either end. Must be able to handle that at the full output that I specify and not saturate at the currents I plan on using.

Thus far this has been a successful concept as the amps using them measure to those limits. To be sure the math and design issues are better left to the pros. Also the trannies I get this way are significantly larger, heavier and to a certain extent more costly. The weight and size are roughly double a typical off the shelf trannies. I do not use toroids for outputs, only standard designed ones.