Dear Sir salbayeng,
your schematic is designed for single supply operation, as it has a rail splitter (R11,R12).
Dont you think, depending on Op-amp, power supply should choose ?
Whats the benefit of -Ve and +Ve ? Does not it amplifying signal on both side?
What are the drawback of single supply ?
My main circuit at first post, if you can see my supervisor suggest me to keep the cascaded 3 equalizer in in series !
That means signal from microphone with certain frequency could trapped in one frequency selected portion.
In this time we observed both boost and buck operation gain.
Dont you think its a wrong idea as background noise could directly appear to the post amplifier for hearing ? or gains are multiplied ?
If you take a look on your circuit, one portion of equalizer directly connected to the output, having in parallel action.
In the Bass control section, R8 is connected other Mid and Trable are connected with capacitors.
Make sense ! Frequency is inversely proportional to capacitor impedance.
During operation, one impedance is active while inactivate others.
Those make huge change on gain.
Let me think it more, because I need a noiseless and distortion free like others.
Hearing aids have a fairly limited frequency range (not as much as 100Hz to 10kHz) so you could squash together the bass and treble cutoffs.
Well, did you see senior member Audioguru says what in this text? look at his graph.
Keep in touch.
I need your help.