I’m working on a preamp and would like to compare the FR at different stages of processing. For example, I would like to look at the FR going into the tone section and compare it with the output. Ideally, I would like to subtract the input FR from the output FR. Perhaps using the L and R channels of the QA402.
In summary, I would feed one of the QA402 outputs into the preamp. Hook the left channel input to the input of the tone, right channel input to the output of the tone section, subtract the two and look at the result.
Why not just use the File>Export Data>Export Frequency Series and do your subtractions and plots using Excel ? Today I am updating my post as I am in a similar situation. The overall frequency response of my integrated amp at the speaker output has a high frequency rolloff that is not there out of the preamp (both channels are about the same), at either 1w or 30w. My thinking was to use one of my scope probes set to x1, and hook that up to the left channel input, and probe different parts of the circuit. Of course, I would be mindful of the voltages in the area that I would be probing since I would not want to overload the QA402. Of course, depending upon the kind of problem, you could just inject a single tone and monitor it with a scope along the path…For grins here is what I am seeing:
