Hi,

We have a question with regards to the ADAU1701 and Sigma studio that we hope you can help with.

We are trying to simulate a constant current output from a voltage amplifier (power amp) when driving inductive loads..

We have been working with the ADI ADAU1701 development kit and the DSP has proved more than capable of providing most of the functions we require but when it comes to equalising for the load it has proved more difficult.

We have tried using parametric boost/shelf functions to try and achieve this but these require the manipulation of several variables to try and approximate what we want to achieve.

And so finally to my question.

Are you aware of any functions in Sigma studio that can replicate a gain stage with an output that rises at constant 6db/octave from a single specifiable frequency?

Hope you can help.

Hello Andrew,

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Edit-- The project file had its filters set for 96 KHz sample rate, but the -1701 register core control was set for 48 KHz (1x, 1024 instructions). Thus the simulated responses were correct, but the filters would provide incorrect response (corner frequency half the expected value) if run on the hardware. The attached project has been fixed. The spreadsheet remains the same. ***By mixing the output of a differentiator (+6 Db / octave slope for all frequency) with a straight flat gain, you get a response that remains flat with increasing frequency until the differentiator's output dominates -- then its rising response takes over. Both these functions can be combined into a simple 2-tap FIR filter, as shown below:

A FIR differentiator's two coefficients are of opposite polarity, while a straight gain is just one positive coefficient. The attached spreadsheet calculates the combined filter's coefficients given the sample rate and the desired corner frequency.

Best regards,

Bob