Hi,
As part of a 3rd year technical project i am designing a portable, battery powered parametric EQ, i have a working design and am now at the stage of specifiying the components required for each band.
band 1 : 100Hz-6kHz centre frequency range
band 2 : 6kHz- 14kHz range
band 3 : 14kHz-20kHz (this can be slightly less than 20kHz as most cant hear this high)
the ranges are specified by the components in a gyrator circuit (simulated variable inductor).
I am aware of the equations to establsh the resonant frequencies of an inductor and aware of the equation to work out the inductance of the gyrator circuit, the bit im struggling with is altering component values to achieve the desired bands, when i widen them the performance of the filter at other frequencies becomes unstable.
Any help would be great, LTspice file and potentiometer sub and symbol files are attatched.
As part of a 3rd year technical project i am designing a portable, battery powered parametric EQ, i have a working design and am now at the stage of specifiying the components required for each band.
band 1 : 100Hz-6kHz centre frequency range
band 2 : 6kHz- 14kHz range
band 3 : 14kHz-20kHz (this can be slightly less than 20kHz as most cant hear this high)
the ranges are specified by the components in a gyrator circuit (simulated variable inductor).
I am aware of the equations to establsh the resonant frequencies of an inductor and aware of the equation to work out the inductance of the gyrator circuit, the bit im struggling with is altering component values to achieve the desired bands, when i widen them the performance of the filter at other frequencies becomes unstable.
Any help would be great, LTspice file and potentiometer sub and symbol files are attatched.
IMHO, 100 Hz to 6 kHz is a very wide range to cover with a single band, this is almost 6 octaves, where the second band (6 kHz to 14 kHz) is just a little over one octave, and the last band (14 kHz to 20 kHz) is much less than one octave. Also 100 Hz as the lower limit of the lowest band is quite high, you are neglecting more than 2 full octaves below 100 Hz.
You may want to re-think the ranges so that each covers about 3 octaves (e.g. 40 Hz to 320 Hz, 320 Hz to 2.5 kHz, 2.5 kHz to 20 kHz), or just simply one decade. (e.g. 20 Hz to 200 Hz, 200 Hz to 2 kHz, 2 kHz to 20 kHz). By reducing the adjustment range, especially for the lowest band, you will find it easier to make the filters stable at the extremes of the range.
Also this thread would be much better suited in "analog line level".
You may want to re-think the ranges so that each covers about 3 octaves (e.g. 40 Hz to 320 Hz, 320 Hz to 2.5 kHz, 2.5 kHz to 20 kHz), or just simply one decade. (e.g. 20 Hz to 200 Hz, 200 Hz to 2 kHz, 2 kHz to 20 kHz). By reducing the adjustment range, especially for the lowest band, you will find it easier to make the filters stable at the extremes of the range.
Also this thread would be much better suited in "analog line level".
Last edited:
ah, ok
well the aim of the EQ was to focus on vocal frequency elements and have some ability to attenuate high frequency noise hence my first band allocations.
On a second note im having trouble working out required components for each band, i understand that the caps (C1 and C2) alter the resonant frequency of the gyrator in combination with the pot but how would i relate this to lower and upper frequency limits? for example one early (and is far as i can work out incorrect) assumption would be that one controls the lower limit and the other the upper limit.
my question really is what is the relationship of each component to each range feature?
Sorry for the incorrect posting area, will know from now on when creating threads
well the aim of the EQ was to focus on vocal frequency elements and have some ability to attenuate high frequency noise hence my first band allocations.
On a second note im having trouble working out required components for each band, i understand that the caps (C1 and C2) alter the resonant frequency of the gyrator in combination with the pot but how would i relate this to lower and upper frequency limits? for example one early (and is far as i can work out incorrect) assumption would be that one controls the lower limit and the other the upper limit.
my question really is what is the relationship of each component to each range feature?
Sorry for the incorrect posting area, will know from now on when creating threads
- Status
- Not open for further replies.