I'm currently looking to build (or purchase) a balanced 1khz notch filter for aiding in measurements. And am not too sure where to look.
There is plenty of advice for single ended options, but almost nothing for balanced.
The twin-T design has been suggested but i'm not sure if simply building a symmetrical version of this would work or not. But also how tightly tolerances would need to be controlled in order for this to work properly. As I don't want one side to be attenuating 998hz and the other 1002hz etc.
Would anyone be able to advise on this? Even commercial options like the QA480 have a fair bit of unit variance and so simply buying two of those to use in a balanced configuration could be problematic.
Thanks!
There is plenty of advice for single ended options, but almost nothing for balanced.
The twin-T design has been suggested but i'm not sure if simply building a symmetrical version of this would work or not. But also how tightly tolerances would need to be controlled in order for this to work properly. As I don't want one side to be attenuating 998hz and the other 1002hz etc.
Would anyone be able to advise on this? Even commercial options like the QA480 have a fair bit of unit variance and so simply buying two of those to use in a balanced configuration could be problematic.
Thanks!
If you are building a 1kHz filter yourself it isn't hard if your components are high precision and minute adjustments can be made when you are in the final stages .
In one of JLH,s articles on one of his RIAA stage designs he paralleled up components to get an extremely high accuracy of reproduction , near was not good enough and it worked , I built it at the time .
I have also built several THD meters including one of John,s designs using 10 turn quality potentiometers.
This allowed a null down to below 0.001 % to be adjusted by hand and quite a sharp one .
In one of JLH,s articles on one of his RIAA stage designs he paralleled up components to get an extremely high accuracy of reproduction , near was not good enough and it worked , I built it at the time .
I have also built several THD meters including one of John,s designs using 10 turn quality potentiometers.
This allowed a null down to below 0.001 % to be adjusted by hand and quite a sharp one .
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