I have however noticed some strange behavior with the LM3915’s, my circuit’s dot/bar pin would not function (I have 2 IC’s, 7 on backorder), and some LED functionality was unreliable, requiring the voltage to be up to 18-20V. The datasheet explains it as oscillation occuring, however trying to get rid of it seems to be very hard (plus I can’t seem to view it on my scope at all). I can’t seem to duplicate the oscillation after boosting voltage from 12 to 20V and adding the ‘recommended’ cap from the datasheet. I don’t have any tanatlums handy (well, I have SMD salvaged ones but those aren’t all too reliable/trustworthy), but the electrolytic solves some of the oscillation problems, as well as the undervolt. The oscillation/undervolt is characterized by the peak volume LED being lit the brightest with all the other lower signal LED’s dimming relative to which peak LED is selected.

Its a scary coincidence that I’m using the LM358 for the fliege filter, and almost the exact same cap values. I might as well use his table since those resistors seem more available. I only picked a 7 band spectrum analyzer cause its the number of LM3915’s I could get under $20 CDN (pre-tax of course).

He too uses Fliege filters for a 7-band analyzer. I’m attempting to build this, but instead of nixie tubes I’d like to use LM3915’s to drive the LED’s. This is quite similar to what you are attempting.

Perhaps his schematics will help. I have very little experience with circuit design, so I hope you carry forward with your project. I’m very much looking forward to your next post, best of luck!