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Really, really wierd question: but does the color of the LED affect the tone of the clipping? and what variable determines it if so, luminous intensity? Wavelength? what?

thanks for the help in advance!

Forward voltage drop.

A diode, of any kind, requires a certain amount of voltage before it conducts. With normal silicon diodes, this about .6 volts. So, anything above .6 volts will go through the diode, usually to ground-- thus, anything above .6 volts is clipped. So, the more of the signal that's above .6 volts, the more the signal will clip.

(it's more complicated than that)



LEDs have much higher forward voltages. 1- 2 volts. They don't vary just by colour, but by type.

Here's my readings. One with cheap read LEDs that I generally use for clipping diodes, and some ultra-brights I use for indicators:

Cheap red: 1.6
Orange 1.8
Yellow: 1.82
Red: 1.772

White, UV and green didn't give a reading. I'm sort of thinking that means they were too high or have some sort of capacitance to them. I'll check the specs on my meter.

I have used different colors for slightly asymmetrical clipping. It's subtle.

so, if i used red LED's i would get harsher (i.e more) clipping than if i used yellow, or am i getting this backwards?

(EDIT):i ask because i intend to build a preoco rat clone in a month or two and will include some mods from beavisaudio and wondered whether experimenting with different colours of LED's would effect this mod http://www.beavisaudio.com/projects/FKR ... rMouse.gif (its on the left of the page)

The difference between using both red and both yellow would be negligible. You won't notice it at all. You're better off putting LEDs on one side of your clipping toggle and a different type of diode on the other.

ahh thanks, i'm new to this stuff so i appriciate your help!

The difference between the 3 brighter types are so close you wouldn't notice.

The difference between the cheaper red LED and the others is as significant as the difference between diodes that I honestly do notice the difference between. But, since LEDs clip so little, it's realistically negligible.

I use these because they're cheap and work great:

http://www.mouser.com/Search/ProductDet ... L-LX3044ID

But now Mouser has these:

http://www.mouser.com/ProductDetail/Kin ... 9frztbg%3d (and they come in different colours)

If I was doing something where you could see the LEDs, I'd use the more expensive, brighter ones since they'd light up more.

thanks for the help guys, i think i'll use what ever's available at my local electronics shop as i'll be picking bits up everytime i get some spare money. Sorry for distracting from the TS's question btw.

McSpunckle wrote:White, UV and green didn't give a reading. I'm sort of thinking that means they were too high or have some sort of capacitance to them. I'll check the specs on my meter.

My DMM generally can't read past 2.0v on forward voltage.

My Peak Atlas DCA, however, can read up to 5.0v for forward voltage. Some of the water-clear LEDs are 2.5v to 3v.

culturejam wrote:

McSpunckle wrote:White, UV and green didn't give a reading. I'm sort of thinking that means they were too high or have some sort of capacitance to them. I'll check the specs on my meter.

My DMM generally can't read past 2.0v on forward voltage.

My Peak Atlas DCA, however, can read up to 5.0v for forward voltage. Some of the water-clear LEDs are 2.5v to 3v.

Checked the specs on mine... 2.4. So I guess those are at least 2.5. It's giving an open reading, and the LED is lighting up, soooo.

I guess those would definitely sound different... it'd take quite a bit of gain to clip them.

Also, I just googled the Peak Atlas DCA, and I feel as if I need one.

McSpunckle wrote:Also, I just googled the Peak Atlas DCA, and I feel as if I need one.

Dude. You must get one. It rules.

I got one last Xmas. It's been so handy to have (and it's saved me money).

I just ordered their Atlas DCR as well, which is the same thing but for passive components, including inductors. It measures down into the low pico-farads accurately, which is cool.

Those two Peak meters are on my Christmas list.

They've been on my xmas list for too many xmas's now

remember you can measure the forward voltage with the voltmeter.

just make a test circuit with a battery say 9v through a 470 ohm res then the led. take your voltmeter and measure the voltage across the led while its on. Although the drop changes a bit based on the current flowing through it, it will not change that much. most voltmeters go well beyond the forward drop of any led

But that takes more work than using the diode test function, and, as such, is not useful to me.