power-on circuitry? also couple cmoy questions

[Soymilk]

well that was fast, already got it. i guess 7.50 for one day shipping isnt too bad
 
still wondering about the opamps (would the ones used for the l/r channels in a ppa be fine in a cmoy too). here's a list of what i have:
 
AD797AN, AD8065AR, AD823AN, AD8066AR, AD8397ARZ, AD744BQ,  AD8610BRZ, AD825AR, AD843BQ, AD829AQ, AD8620BR, LM4562NA, OPA637AP, OPA627AP. iirc some of these were options for only the ground channel of the ppa though.

 

[gimble]

Yeah, I saw their shipping. Bleh. Still, you have to keep in mind that they aren't exactly targeting hobbyists. For the op-amps, you might start by checking them against this list. It's a good starting point at least.
 
I was fiddling around on the Jameco catalog page and this came up:
 
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_1953680_-1?CID=PDF
 
It looks to be a center-negative version of the above power supply for a buck cheaper. Unless I'm missing something. It's roughly 3AM, so, who knows.

 

[Soymilk]

any of the opamps should work fine in the cmoy though right?
 
also apparently a few of the opamps i have are the tiny surface mount package rofl. i never really checked them all when i first got them, but they were free so who am i to complain plus i can just get an adapter.

 

[MisterX]

 
Quote:

 any of the opamps should work fine in the cmoy though right?

 
There are a couple of them that will not work in a CMoy.
The AD8397 is an example but that is the preferred op-amp for the left and right channels in a Mini3 so....

 

[Soymilk]

since i'm lazy, i've narrowed it down to two opamps since these are the only two dip-8 dual opamps i have out of my random collection: lm4562, ad823. any direction on where to go between these two? if not, im gonna just go with the 4562 since it's a bigger number and bigger means better right

 
also, if you havent seen my other thread about controlling an led with the volume control and may be able to answer a couple questions, a look here http://www.head-fi.org/forum/thread/512714/volume-controlled-led would be appreciated

 

[Soymilk]

hmm, so putting it in series (+v -> resistor -> capacitor -> led -> ground) makes the led fade to nothing when the power turns on, it starts full power and fades out. i was going for the opposite effect D:
 
through various ways of putting the capacitor with the led/resistors, the closest i've come is getting the led to fade out after cutting power, i havent found a way to make it fade in when you turn on power. can anyone point out what im doing wrong?

 

[Soymilk]

at this point i figure i actually want an inductor, not a capacitor in there.

 

[cobaltmute]

Place the capacitor in parallel with the LED to ground.

 

[Soymilk]

hm, i thought i tried that. it might also be that i need a larger capacitor there. we'll see

thanks.

 

[Soymilk]

ya ended up needing a much larger capacitor to get any noticable fade-in D:

 

[cobaltmute]

There is some formulas on this page that may help:
 
RC Time Constant