Have you ever missed an obvious solution to an engineering problem?
I'm starting to design an audio line mixer for myself, and I decided to make some distortion measurements of the final product when the time comes. I had a solution to do this (in lieu of obtaining super-expensive measurement equipment), which has been in the back of my mind for a while. It involved making a very narrow notch filter to remove the test frequency, and amplifying the leftover signal. This is a pretty standard solution, yes?
I did some Google searching today about distortion measurement, and came across a solution so obvious I felt like an idiot for not thinking of it:
Difference amplifier.
As in: (DUT output) - (signal source) = DUT distortion+noise (and amplified)
How did I not think of SIMPLE SUBTRACTION before jumping to creating a filter narrow enough to remove a single frequency without affecting its harmonics?
Also, as an added bonus, this search made me aware of some opamps (referenced in the articles I found) which have SUPER low distortion figures, and aren't terribly expensive. Quite useful for audio!
I'm starting to design an audio line mixer for myself, and I decided to make some distortion measurements of the final product when the time comes. I had a solution to do this (in lieu of obtaining super-expensive measurement equipment), which has been in the back of my mind for a while. It involved making a very narrow notch filter to remove the test frequency, and amplifying the leftover signal. This is a pretty standard solution, yes?
I did some Google searching today about distortion measurement, and came across a solution so obvious I felt like an idiot for not thinking of it:
Difference amplifier.
As in: (DUT output) - (signal source) = DUT distortion+noise (and amplified)
How did I not think of SIMPLE SUBTRACTION before jumping to creating a filter narrow enough to remove a single frequency without affecting its harmonics?
Also, as an added bonus, this search made me aware of some opamps (referenced in the articles I found) which have SUPER low distortion figures, and aren't terribly expensive. Quite useful for audio!