Running Uproar at 18v?

[timbo_93631]

Just for kicks I have been messing with opamps in my Uproar, different types (4580D, TL072, BURR BROWN OPA2134PA) and stacked opamps with various combinations.  This got me to think about running it at a higer voltage.  After checking all the datasheets the input voltage min is 2v and max is 18v on all types with the exception of the 4580D datasheet which had a note that stated the max was 18v but the recommended max operating voltage is 15v.  If I have two 4580D's stacked what happens to that voltage rating?  I don't think it would be doubled like a passive component.  Anyone know?  Also if I plan on regularly running my uproar at 18v will a 4.7k CLR be enough to protect the LED?

[jkokura]

Yes the 4.7K will be enough, but it may become brighter than you'll be used to. In that case try going with a 10K, which may not be 'super bright' at 9V, but will be bright enough, and will be a more reasonable brightness for the 18V.

I was using 1K's at 9V until I found I was ruining the darkened stage effect...

Jacob

[oldhousescott]

This got me thinking about constant current sources for the LED and I found out there is a class of devices called "current regulator diodes" or "current limiting diodes" which are actually active devices that will regulate a current across a range of applied voltage. These might be the ticket for LED drivers in pedals that accept 9v to 18v input. Mouser PN 954-S-103T is a 10mA/50v max current regulator diode. They come in different mA ratings if you like brighter or darker illumination. Just substitute for the CLR in the circuit. Someone should grab a few and see how well they work.

[timbo_93631]

I left it as is, the LED I have in there is a ratshack diffused green 5mm, with 4.7k CLR it was fine at 18v.  I tried it with two sets of stacked IC's, TL072/OPA2134PA fo IC1 and TL072/4580D for IC2.  Sounded pretty dang smooth at practice last night.