Other Parts Discussed in Thread: OPA2132
Good afternoon. I need to create an equalizer with non-standard frequencies. That is, these frequencies are not spaced at the same intervals.
I found the app webench.ti.com/.../filter-type. But I couldn't figure out how to use it.
I would be very grateful if you show by example the calculation of such a filter for the middle position and for values of 80 and 16000 Hz. The maximum/minimum input and output frequencies are 20 - 20000 Hz.
Thanks!
The input impedance of such a circuit is R1 / 10. What value of R1 would you recommend?
The input signal will be taken from the mixer based on the OPA2132.
Hi Gennadiy,
Take note of the formulas on the page as they will vanish once you start doing calculations. First thing is to enter a center frequency, a Q factor (or a damping ratio but Q makes more sense here) and a gain. Press calculate at the bottom and something like this will appear:
As you can see it gives us component values and a lot of characteristics that give a good starting point. If you scroll down you'll get a bode plot. Take note of the capacitor ratios on the right. We'd like the input impedance to be pretty high, so if we maintain the same capacitor ratio but make them smaller, we can increase the resistances.
However this becomes less of an issue if the output impedance preceding this stage is very low. If I understand your diagram correctly, the output of the Panel_OPA2132 goes to the EQ stage correct? This means the input impedance doesn't have to be so high.
As far as preventing damage, I'd simulate one EQ filter at a time to make sure you're getting the result you want; then simulate them in the same circuit like you have shown before prototyping or experimenting. As long as your voltage supply is safe and you are not providing inputs much higher than line level (2Vrms) you shouldn't have much risk for damage.
Best regards,
Jeff
