NonLinearity Viewer

[Zero D]

I was looking at DPC Manual & saw this.

"XMAX

Nonsymmetric nonlinearities can be studied by applying a sinewave signal to the driver at a fairly large power (enough for high excursion levels) and utilizing a stroboscope. Sweep up and down in frequency to observe DC-offsetting. The driver will simply be moving its operating center / rest position either in or out of the air gap as if a DC-current had been applied to the signal. Even order (primarily second) harmonic distortion creates this behaviour."

I emailed Claus Futtrup & asked for permission to quote the above, which he kindly agreed to

It occured to me that a device to attempt do that might prove useful. So i've designed one ! I havn't built it, but have simmed it, & it seems to do what's required.

The block diagram shows how to hook it up. The circuit diagram shows the components required & connections. The OpAmp doesn't need to be expensive, for eg, a TL071 would do. 1 White LED might be ok if bright enough. An LED torch with the batteries removed, could be ideal for this. I would expect the viewing to be done in darkened conditions, for easier analysis.

I've posted it in here, because it's mainly bass related, i expect.

Any suggestions etc would be welcome

EDIT

After reviewing, i realised the original circuit full wave rectified the audio ! Doing that doubles the frequency to the LED, when it needs to be the same rate as the sig gen f. Now it is, my bad !