Sorry if this is a newbbie question but then....does that feedback turn the comparator to schmitt trigger type?
After having done a recent design with super fast comparators, this positive feedback accomplishes one thing. This gets you hysteresis control. You can ultimately control the "jitter" better with positive feedback.
A comparator with a static comparison voltage is already a schmitt trigger of sorts. The trigger voltage(in your schematic snippet) is set by the division of R11 and R3 to R10.
As Brad mentioned, only parts that are specified to be immune to latching up can be used with positive feedback otherwise they will just rail out and overheat.
One trick that you might try is to add a small ceramic cap in parallel with each LED. I've seen that trick on some higher end equipment that uses switched LEDs in sensitive environments although I've never done it myself and can't tell you it's true limitations. Some of the fast transients/higher harmonics are softened by the cap, essentially smoothing the switching waveform.
*EDIT* I just read JohnRoberts post about the relay:
consider adding some capacitance across relay winding to slow down edges.
This is in fact what I was talking about. I'd say 100pf or less depending on your currents.
*EDIT* I see that you chose 33pf. Sounds good to me, I would have chosen 47pf myself.. :green:
Lets not forget that LAYOUT can have a very critical effect on this type of stuff. From dealing with RF layouts and problems like this with power supplies near RF traces/parts I can tell you that there are a million ways to screw this up and about 3 ways to do it right.
Decoupling is critical here too.
As for the jack clicks, some circuits I've seen use a switched jack that makes/breaks ground on a secondary circuit. You could use this to control a PFET that would control the relay. This way you have to have the plug all the way in the jack before the circuit activates.
Just an idea.
