Forward voltage and low impedance. I built three of those amps where the output tubes were bottom-lit from the LED array. Delightfully cheesy, yet very functional and inexpensive. There's photos on my website.
Now who is being silly? I guess using the LEDs for bias too can be pleaded in mitigation, and valve-lighting saves totally wasting the photons.
They brighten and dim with the music when I turn up the volume, an added bonus. Nice clipping indicator as well.
Am I allowed the IR LEDs in my phono preamp?
Am I allowed the IR LEDs in my phono preamp?
Hi
I understand this is a bit overboard for the kind of solution you're looking for.
-a piece of tape will most likely be the best solution.
But seriously..
The best way to 'dim' an LED is to flash it.
LED's characteristically are not easy to dim with DC. They like to either be on or off, and to get all of their rated voltage.
They can however operate extremely fast (kHz, or even MHz).
You will need a digital circuit that can output a high frequency (so you don't see the flash) square wave with an adjustable duty cycle ('on time' vs 'off time').
This is probably easier and cheaper than many people realize.
I don't have a schematic with me now, but maybe I'll post back if there is an interest in building a digital LED dimmer.
-just for the hell of it
I understand this is a bit overboard for the kind of solution you're looking for.
-a piece of tape will most likely be the best solution.
But seriously..
The best way to 'dim' an LED is to flash it.
LED's characteristically are not easy to dim with DC. They like to either be on or off, and to get all of their rated voltage.
They can however operate extremely fast (kHz, or even MHz).
You will need a digital circuit that can output a high frequency (so you don't see the flash) square wave with an adjustable duty cycle ('on time' vs 'off time').
This is probably easier and cheaper than many people realize.
I don't have a schematic with me now, but maybe I'll post back if there is an interest in building a digital LED dimmer.
-just for the hell of it
Does your switching proposal affect the audio circuits and/or sound quality?
I have found that DC brightness adjustment works very well for indicator LEDs.
LED/LDR volume controls also use DC control.
LED voltage references use DC.
I have found that DC brightness adjustment works very well for indicator LEDs.
LED/LDR volume controls also use DC control.
LED voltage references use DC.
No. It wouldn't have to.
-assuming it's a power indicator.
If you want to make a level meter, then you'd have to isolate it somehow (optically?).
It would depend a lot on the amp, and what you were doing with the LED.
But the short answer is no.
My suggestion relates generally to dimming an LED.
-how it is integrated into a piece of gear would need more specific consideration.
What I had in mind was a simple circuit that one could add to a power indicator which would have something like a small pot to adjust the brightness.
In that case the audio path would not be affected.
-assuming it's a power indicator.
If you want to make a level meter, then you'd have to isolate it somehow (optically?).
It would depend a lot on the amp, and what you were doing with the LED.
But the short answer is no.
My suggestion relates generally to dimming an LED.
-how it is integrated into a piece of gear would need more specific consideration.
What I had in mind was a simple circuit that one could add to a power indicator which would have something like a small pot to adjust the brightness.
In that case the audio path would not be affected.
An LED is a diode. It's light output might not be strictly proportional to current, but not far off. Therefore to dim a DC powered LED just give it a bit less DC. Only if you are worried about ultimate efficiency and not worried about noise would you employ a chopper circuit instead.
Bias LEDs which vary with the music remind you that most amplification devices add second order distortion, so I guess that is useful. Or they remind you that the light output is not strictly proportional to current, which in the context is less useful. IR LEDs are fine, provided you don't accidentally burn a hole in your retina.
Bias LEDs which vary with the music remind you that most amplification devices add second order distortion, so I guess that is useful. Or they remind you that the light output is not strictly proportional to current, which in the context is less useful. IR LEDs are fine, provided you don't accidentally burn a hole in your retina.
I'm sorry, I had difficulty reading this.
Actually, bias LEDs which vary with the music remind me that my amp is biased to AB.
Dimming LEDs can be a bit hit and miss. If you reduce the DC voltage (ie with additional series resistance) eventually the LED will cease to light at all. The best bet is to just reduce the amount of light that can escape with a filter of some kind. A blue LED will be seriously reduced in brightness by a RED filter. You could try using the lens paint that autotraders sell to repair broken tail light lenses. Flashing will certainly work but may compromise your system with additional noise and certainly additional complexity.
5 cent series resistors have worked just fine since the invention of led's....simple, cheap, effective and reliable...why do some find the need to complicate things. 🙄
Eric.
Eric.
If you are not comfortable replacing or adding the series resistor, try a drop or two of Elmer's Glue on the lens...once it dries it is opaque. You can add another layer if it's not enough or just peel it off if it doesn't work for you. Look for another solution then...
If you are comfortable, lift one end of the resistor and clip on a 10k to 20k pot in series and adjust to your eyes' content. You can then measure total R and replace with an equivalent resistor.
If you are comfortable, lift one end of the resistor and clip on a 10k to 20k pot in series and adjust to your eyes' content. You can then measure total R and replace with an equivalent resistor.
Experiment and connect a resistor in parallel with the LED to bypass the current. Little tricky but do-able and is advantageous.
Gajanan Phadte
Gajanan Phadte
Why not carefully mask of around the led with some quality masking tape. Then get some smoke paint and then do a light quote. Led still usable and simply done?
- Status
- Not open for further replies.