I just built the second one and it took maybe 30 seconds.Trimming a Twin T to null its output.
How difficult, it is ?
How many iterations going around at the two trimmers, does it converge smoothly to the final result ?
You just dip each one - the first iteration is only a few dB.
Rinse, lather, repeat and it converges pretty fast.
Maybe 5 to 6 iterations.
I use a scope for it - doing it with the FFT is slower.
True.You should have noticed the two 1K trimmers have different sensibilities. There is a x2 difference in how hard they pull
I had a whole tube of 1K trims and wanted to use them on my Protoboard.
Also wasn't sure how much range I'd need.
I do have a 500Ω in as a gain trim so I should make the BOM have two.
I want to make a "twin-H" where no filter element is grounded.In earlier posts, you mentioned "differential notch filter."
Two twin T connected together at a virtual ground node.
A twin H. That would be made of five 16K resistors and five 10nF capacitors.
You could also call it a "twin-twin-T" or "double twin-T."
What I have now is two twin-T connected together at ground which is indeed not balanced.
For checking the oscillator's balanced output I decided to try them differentially by hanging a CMR stage on the output.
The twin-H INA would obtain a bias current path through the twin-H to the input connector which would have 100K to ground bias resistors.
The 100K input resistors and the post-INA CMR stage would be the only points to touch ground.
This maintains a common mode gain of "1" in the INA and which then provides CMR in a post-INA CMRR stage.
My MM phono preamp board would be a good way to follow the twin-H.
I have enough 10 nF 1% to make a true twin-H.
I think I need scale the resistor values to maintain the same Fc.
Do 5X 15K9 and 5X 10 nF sim at 1 kHz for differential inputs?