FM Modulation distortion

[soggybag]

I found this in the Stompbox Cookbook. It looks interesting. The drawing ran off the page so the output buffer is missing. I'll redraw it and post it again if anyone is interested.

I set this up on the breadboard and couldn't get it to work. Suggestions questions comments welcome.

[Paul Perry (Frostwave)]

Well it's a fairly experimental & temperamental thing to run on a breadboard.
Note it says in the book that one major problem is coupling of the 55 carrier to the 567, and you may hav eto use separate batteries for the two sections!

I haven't tried it myself, but I think the theory is that the 7555 oscillator is modulated by the audio input & then the FM is demodulated by the 567. And nonlinearity (= distortion) is caused by either overdriving the 7555 (effectively clipping at one side) and by futzing around with the operation of the 567. I'm not optimistic.

[soggybag]

Thanks for the comments. The 555 seems to be working. But the 567 does nothing. I get no output and the LED, which the notes suggest should light, never does. I tried running this with two PS, still no luck.

[dano12]

I haven't seen that configuration on the LM567 before on pin 8. I usually leave it floating. But its not like there are a ton of 567 circuits out there to compare against

One thing I found is that going over 9v+ on the 567 will cause it to not do its magic, don't know if that helps....

Finally, here's a 567 design that I worked up. If you can't get the cookbook one working, feel free to give it a try.