[sdiy] Harmonic Sweetener: Jules Ryckebusch May 12, 2000

[NSSINC]

Good morning,

This circuit was posted here about 20 years ago...

I tried it then and it didn't work for me, and I have just tried it 
again with the same results.

The filter section of the circuit (IC2) does not seem to operate as 
intended.

The output swings to one of the power supply rails and stays there.

Is there any chance the op-amp input polarity on the highlighted filter 
section is inverted?


https://www.noyessoundstudio.com/files/JR_harmonic_sweetener_filter_hghlight.pdf


The filter circuit described here seems to indicate as much:


https://www.noyessoundstudio.com/files/all_about_circuits_detail.jpg

From- 
https://www.allaboutcircuits.com/video-tutorials/op-amps-low-pass-and-high-pass-active-filters/


And my first attempt at dong a spice simulation reflects what I'm seeing 
in the real world. It works ok if I swap the input polarity, but latches 
to the rails as drawn.

https://www.noyessoundstudio.com/files/simulide_filter_working.jpg

https://www.noyessoundstudio.com/files/simulide_filter_NOT_working.jpg


I swear, way back in the day I built it on breadboard from the actual 
article in Electronic Musician and it worked great. I have yet to find 
my copy of the article or one on the web.

Looking for a sanity check, is it me??

Thanks for taking a look.


-Al