DSP Robotics Support

Playing around with Waveshapers and it raised a question.
Say I have an analogue 'black box' and I would like to design it's digital equivalent.
While I can easily measure its frequency response and static dynamic range response, is there a way to measure its 'waveshaping' ability?

Let's assume the black box is this (just a stupid example):
Yout = Xin * sin(Xin) , for Xin > 0.5
Yout = Xin , for Xin < 0.5

Is there a way I cam measure this and 'backwards' engineer a similar function?
Maybe if I choose as an input a full range (between -1.0 and 1.0) sawtooth so that I can see all possible sample values - and view it on a scope? Step response? Impulse? Other method?

It's a theoretical question, so let's assume I have all existing measurement gear...

Hi Rocko, I don't know if this is what you are looking for, but I made an analog to digital waveform, check it out!
The reverse engeenering generates a waveform based on the analog input, all you have to do is use the wave generated and put it into a Waveshaper.

- Wassaka

Hi,

Can you explain how to use it and what is it supposed to do?
Sorry, but I did not get you on this one

Rocko wrote:Hi,

Can you explain how to use it and what is it supposed to do?
Sorry, but I did not get you on this one

Basically what you do is give samples linearly (sawtooth) from -1 to 1. These samples enter your analog processor (for example a valve distorter) and the schematic receives the output values of the analog processor and analyzes them. The result is a waveform of -1 to 1 that is able to emulate your analog distorter by means of a waveshaper.
In short: it is a tool that allows analyzing an analog processor and emulate it digitally by means of waveshaping.
I don't know if it's exactly what you were looking for ...

Rocko wrote:Hi,

Can you explain how to use it and what is it supposed to do?

Using it is very easy, you simply modify the parameters in the "CONTROL ZONE" and connect the output of the schematic to your analog processor. Then you connect the output of the analog processor to the input of the schematic again, and press the "START" button. You will see how the output waveform of your analog processor is analyzed. Finally, the waveform generated by the schematic can be used in a waveshaper to emulate your analog processor. In the schematic there is an example function "Tanh (x)" you will have to eliminate it, since it is only an example.

OK

Thanks for the explanation. Ill give it a few runs and get back with some inputs.

Well, I test run this module on quite a few cases. Its interesting.
For measuring the signal of a simple analog circuit. like a single amplification stage, it is a great solution ! Many thanks !


Things get more complicated when it is a more complex analog box, like, if it includes a DC block (High pass filter at say 10Hz) - then the measurements includes the response of the DC block filter.

Can you think of a way to measure a (say) band limited device? Assume a band is limited between 20 and 400 Hz (bass exciter) ?

Rocko wrote:Well, I test run this module on quite a few cases. Its interesting.
For measuring the signal of a simple analog circuit. like a single amplification stage, it is a great solution ! Many thanks !


Things get more complicated when it is a more complex analog box, like, if it includes a DC block (High pass filter at say 10Hz) - then the measurements includes the response of the DC block filter.

Can you think of a way to measure a (say) band limited device? Assume a band is limited between 20 and 400 Hz (bass exciter) ?

To avoid that DC Blocker you must increase the frequency of the burst to 20 Hz (higher than 10Hz).
If we are talking about analogue equalization, this schematic is totally useless ... In that case, try an impulse response to see the spectrum generated by the analog processor.
The schematic that I build only works on analog saturators or something similar, it DON'T works in EQs, Compressors, Reverbs, Echoes etc...