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

[oleavitt at proton.me]

Yep! The op-amp filter (IC2 a/b) inputs are swapped in the PDF article. The positive feedback making them act like comparators with hysteresis.


On Sunday, November 17th, 2024 at 9:41 AM, NSSINC <nssinc at hevanet.com> wrote:

> 
> 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
> 
> 
> 
> 
> 
> 
> 
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