[raven1962]

DIY amp I'm looking at:
http://www.theprojectasylum.com/electronicsprojects/musical-instrument-stereo-headphone-amp/musical-instrument-stereo-headphone-amp.html

Original Schottky Diode spec:
http://uk.farnell.com/on-semiconductor/mbr150g/schottky-diode-1a-forward/dp/1651124
 
Has a Schottky Barrier Diode, between power supply and amp.  I don't know enough to find the values, to substitute into this:
http://www.globalspec.com/reference/25593/203279/7-5-diode-mixers

Ideally, the diode in the substitution diagram could be an LED, with the right parts, adding a 'power ON' indicator, without an additional power drain, rather than just putting an LED and resistor in parallel with the amp.

Sure, it takes a long way around (and costs more) but it serves a purpose, while preserving the purpose of the Schottky.  I don't understand the formulas, so I can't backtrack to make up the substitutions.
 
If there's a better diode circuit, to do this, that's fine.  Just trying to fill a gap (as I see it) in the design, by replacing the one diode that is between the power and the amp, with an equivalent circuit, to also use an LED as a Power indicator.

Thanks in advance!

 

 

[DingoSmuggler]

D3 is there for reverse polarity protection of the incoming power.
The reason it will be a schottky is just for the lower forward voltage drop, but a general purpose rectifier would be fine also.
No, you shouldn't use an LED here.
 
If you want to wire an LED in there without too much battery drain, just get a 5mm LED with high brightness, but wire it up with a large enough series resistor to only use 1mA of current, or less.

 

[raven1962]

I was guessing, based on location, that it's more of a 'pop' filter/buffer, for the power, which is how I've been seeing it used, in some projects.  Don't plan on using the AC power supply, just 9VDC battery.  I can see needing it for the pop filter/buffer, so the series/parallel diode/resistor layout makes sense, that way, at least to me.  Might also give me a battery-power indicator, if I read it right, though I'm not absolutely sure about that.

I know that I DON'T know, so that's why I'm asking for help.  I have to trust what little I understand of what I read, then ask seemingly stupid questions, but I DO want this done right, first time.  I don't have nice toys to backtrack the circuits, just a DMM that is made for household use.  Going to be using a jury-rigged power-supply, for a soldering setup, so everything else will have to be straight-forward, boom-boom-boom.  I plan on using sockets, rather than soldering ICs in place, so I can tinker with different ICs, at a later date.

 

[Nisbeth]

The only function here is reverse polarity protection. The reason for choosing a schottky diode is that it has lower voltage drop, so while a standard diode could be used it might impact your perceived battery life (because lower voltage = risk of signal clipping).

/U.