Parametric EQ

Hi All,

This EQ frequency range is 500Hz-15KHz. How is that calculated?
I need to limit it to 3KHz-6KHz



Thanks in advance:)
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Active filter circuits come in many topologies, each with its own design equations. Its possible to work out from first principles using network analysis, though usually much easier to find the design equations by searching - here I'm not sure what topology that is, if you have more details or a name for the circuit that will help track it down, otherwise its Kirchoff's laws and lots of complex algebra.
Topology is Wien Bridge, freq. span is defined by C16 (C17) and R49+RV6A (R52+RV6B). Highest 1/ 2* PI()*R*C = 15kHz with 6.8 kOhm, and lowest 0.5kHz with 206.8 kOhm.

Q is depends on R123/R122 voltage divider in positive feedback loop, can't say more precise.