Dimming LED in a dual pedal

[oliphaunt]

I have built a pedal with a simple boost and overdrive in the same enclosure.  Each circuit is independant and has it's own footswitch and LED.  Everything works and sounds great, but the problem is that the OD circuit's LED dims when I switch on the boost.  The boost LED is not effected in any way by the OD.  The LED' hot leads are tied together, then go to a single 4.7K resistor, the straight to the 9V input jack.   Do I need to separate the two, each with their own resistor?  Any other thoughts?  This isn't a big deal but I would like to know why it's happening.

[slacker]

Yeah you need separate resistors for the two LEDs. What's probably happening is that the boost LED has a lower forward voltage than the OD one. As they are tied together the voltage on both of them will be pulled down to the voltage drop of the boost LED which will make the OD one dim.

[R O Tiree]

LEDs of different colours have different forward voltages. So, if one is 2.3V and the other is 1.8V and you're tying them to the same current limiting resistor, then they will both adopt the Vf that is lowest, hence one is dimming.

LEDs also, like any other component, have a spread of values within the same colour.

Provide a separate current limiting resistor and you're sorted.

[R O Tiree]

Snap!

[slacker]

I like your explanation better 

[oliphaunt]

I used a red and orange LED, and putting in a second resistor did the trick.  Thanks!