BURWEN BOBCAT TONE BALANCER - MORE HIGHS SETTINGS
Relative to Balanced, boost at 15 Hz is greater while 100 Hz is lower.   10,000 Hz is 2 dB higher.  The middle range is flat instead of slightly tilted down.   
Once you have near optimum tonal balance, as little as 0.1 dB becomes important.

An inherent 22,050 Hz peak occurs at half the 44,100 Hz sample frequency, made by the HIGH control even though it is designed as a non-resonant filter.
 
W
hen a recording is made, a brick-wall filter prior to Analog-to-Digital conversion prevents input above 20 kHz and resultant aliasing.