Apply a little bit of super glue on the LED, and then dab some baking soda
on that. Instant diffusion 🙂
on that. Instant diffusion 🙂
My amp had an searing red diode. The last time I sent it in for an upgrade, I asked for a solution. He put in a wee potentiometer that can be adjusted. I haven't opened the case to see just how this was implimented since it's now nice and dim. Prior to this I have used a spot of nail varnish.
A lot of the high-brightness GaN and GaAlN monster LEDS have sufficient brightness for pilot purposes at only a milliamp or two of drive current. Choose your series resistor accordingly.
My dad used to repair watches, he used that combo to build up the places where the strap pins connected to on the plastic watches...
DC allows a wide range of brightness from very dim to rather bright. Only when you need to go brighter than the brightest possible DC level, or dimmer than the lowest possible DC level, would PWM be necessary.
The problem with PWM is that it's a square wave with many harmonics, and the signal could induce electric fields or magnetic fields in your audio circuit. There are ways to prevent this from becoming an issue, but the easiest way to avoid audio noise is to stick with DC.
There are two degrees of non-proportionality to the light. First, the LED specifications will show a nonlinear light output as a function of current. Note that the human eye also responds nonlinearly to light, which is one reason why we have gamma curve adjustments for displays. Light response is most useful when logarithmic.
PWM LED dimming is more efficient, but similarly, eliminating the risk of audio noise is more important than ultimate energy efficiency, relative to the overall circuit.
Another interesting thing to note in LED data sheets is that the diode voltage drop increases with current. You are correct that the LED will shut off if the voltage drops below the minimum, but at the opposite end the forward voltage increases as you try to pump more current through the LED.
Note also that blue LEDs have a much higher turn-on voltage than red LEDs.
It really helps to know the exact part number for the LED you are working with, although a potentiometer will probably tell you everything you need to know, provided you have a good meter.
This is a good suggestion for a couple of reasons. Not only does it allow you to experiment without removing any existing parts, it also works with LED drivers that are current-output rather than voltage-output.
I've been dealing with a clock on my night stand that is simply too bright. It has 3 switches for any combination of RGB, but they're all too bright for me (red is the dimmest in this circuit). I finally got fed up and opened the case to find that there are no resistors! It seems that the IC that controls the entire clock function has a constant current driver for the LED, so no resistors are used (that I can see). The only way to dim the LEDs in this circuit would be parallel resistance to bleed excess current. It's highly unlikely that you'll see a current driver on an amplifier's LED power indicator, but it's still useful to know this technique.
Unfortunately, it's a waste of power, but we're probably not concerned about LED power in an audio power amplifier.
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Hi all, as you can see I'm fairly new here but have been lurking for some time and enjoying the forums. I work on Navy ships and won't have much time to get much done while at home this time but will return in 5 to 6 months when I can sink my teeth into some projects.
Interesting thread. I know it's superficial and doesn't have anything to do with the sound quality, but I too am about to make some changes to the meter lighting on a few amps of mine.
I've got two SAE 2400's, a SAE 2600 and a Nikko Alpha 650 I want to have selectable led lighting on and be able to switch back and fourth between blue led, red led, and the stock lighting.
I'm planning on using a three way toggle to switch between lighting and a potentiometer to control the brightness on the blue and red led lighting.
I'll mount the three way toggle on the back of the amplifiers as well as the potentiometer for the led's.
I may end up using a two way toggle if I don't like one of the led colors. Can anybody advise me on what range of potentiomer I should be focusing my attention on. I will be using a chassis mount pot for this and the source will be 12V DC.
Interesting thread. I know it's superficial and doesn't have anything to do with the sound quality, but I too am about to make some changes to the meter lighting on a few amps of mine.
I've got two SAE 2400's, a SAE 2600 and a Nikko Alpha 650 I want to have selectable led lighting on and be able to switch back and fourth between blue led, red led, and the stock lighting.
I'm planning on using a three way toggle to switch between lighting and a potentiometer to control the brightness on the blue and red led lighting.
I'll mount the three way toggle on the back of the amplifiers as well as the potentiometer for the led's.
I may end up using a two way toggle if I don't like one of the led colors. Can anybody advise me on what range of potentiomer I should be focusing my attention on. I will be using a chassis mount pot for this and the source will be 12V DC.
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@Rob41
I'm thinking an LM317 in a constant current configuration would be an easy mod. Something like a 62 ohm resistor in series with a 1k potentiometer. That will allow ~20mA on down to ~1mA for the selected LED.
I'm thinking an LM317 in a constant current configuration would be an easy mod. Something like a 62 ohm resistor in series with a 1k potentiometer. That will allow ~20mA on down to ~1mA for the selected LED.
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