i started this proyect because i have a earset (omnidirectional) wireless microphone and the bass region was causing troubles with a lot of feedback, it started because where i use it they installed a couple of 18 inch subwoofers, so i need to filter the lower frecuencys, so i started searching and found the high pass filter shure a15hp but for the moment i cant afford it, so i started searching how to calculate high pass filters and decided to do a 1st order high pas filter for frequencies lower than 100 Hz
i couldn't find anything easy to do or undestand on the internet so that's how all this invetigation started...
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Step 1: Find the Imput Impedance of Your Device
the frecuency of your filter changes depending on what device you connect them as an example if you connect it on the xlr input of the mixer it will filter frecuencies about 100 Hz and lower but even on the same mixer if you connect it on the "line input" it will filter frecuencies lower than 22 Hz, so investigate the input impedance of the device that you are going to connect to, most audio mixers
here's a simulation on the xlr input:
and here a simulation on the line input:
it's the same filter value but the frecuency filtration changes drastically...
Step 2: Calculate Your Capacitor Values
now that you have the impedance of your device, got to this websites to start calculating the filters the way you want them...
go to this webite and just put your impedance input and your desired frecuency:
you can also make your calculations here:
Step 3: Round the Values to More Standard Parts
you cant get all values of capacitors so you need to look at the chart and find the closest real value to the one that you calculated...
also we will need 2 capacitors for our inline filter because the microphone sends the audio signal using 2 wires and a third one for ground, but we have a problem, when we use to capacitors together like in the illustrations their capacitance value drops in half so instead of being 0.72 uF capacitors, they will act like 0.36 uF capacitors, so we will need to find two 1.44 uF capacitors to solve our problem, but because that value is not available we will get two 1.5 uF capacitors for our low cut filter...
Step 4: Gather the Parts...
just go to your local electronics store and get:
1 x female 3 pin xlr connector
1 x male 3 pin xlr connector
2 x 1.5 uF bipolar (non polarized) capacitors
and 3 conductor cable (a short one will work)
the capacitors i used are very big, but you can get way smaller ones like these ones i found on ebay:
Step 5: Time to Solder Stuff...
be careful when soldering the connectors because you can melt the plastic.
also don't forget to put the tension relieve on the cable before soldering the connector because you will not be able to do it later.
and you are now ready to use your filter to stop:
electric grid hum