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Old 12th May 2007, 07:06 AM   #1
sandyK is offline sandyK  Australia
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Default "don't need no stinkin LEDs"

I found this "Electronic Tweak" on the www.tweakaudio.com website.

4.Get rid of all LEDs. They add noise to the power suppliesand
mess with imaging and purity,neon lamps or such for indicators.,if needed.Power indicators do what ? How do you know when
something is on....it plays....don't need no stinkin LEDs.

Is this guy for real ?

I use a blue LED as a voltage reference for the VAS in my Class A amplifier instead of a noisy 3.3V zener diode, and my amplifier is dead quiet.

SandyK
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Old 12th May 2007, 07:35 AM   #2
Nordic is offline Nordic  South Africa
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I have heard this roumor too...

I also rememember a thread showing how a normal led could be used as a button, as it is sensitive to light also... think it produces a small voltage...(typeing under correction)...

If this is enough to affect sound, is something we need to ask the guys with the scopes...
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Old 12th May 2007, 07:51 AM   #3
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Default Re: "don't need no stinkin LEDs"

Quote:
Originally posted by sandyK
I found this "Electronic Tweak" on the www.tweakaudio.com website.

4.Get rid of all LEDs. They add noise to the power suppliesand
mess with imaging.....
I would say: Intersting, can you tell me more about it What have you found in your investigations?
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Old 12th May 2007, 07:55 AM   #4
sandyK is offline sandyK  Australia
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Default "don't need no stinkin LEDs"

I know that some types of LEDs can be used as photo detector diode of sorts. I find it very difficult to believe that a LED , when passing a current of several mA, will respond to external stimulus at any meaningful level. In the case of a LED panel indicator,so what ? It would have to emit a lot of rubbish to affect anything inside a metal case (or plastic!) I always understood that a conducting LED (using DC) was very quiet
Am I wrong in using a blue LED as a voltage reference? I have seen numerous circuits from Elektor , and others, that use red LEDs for voltage references.
SandyK
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Old 12th May 2007, 08:38 AM   #5
dnsey is offline dnsey  United Kingdom
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Quote:
I also rememember a thread showing how a normal led could be used as a button, as it is sensitive to light also... think it produces a small voltage
So, for that matter, is a neon. I discovered this bay accident many years ago when I built a neon-based sawtooth generator. It worked fine, but the frequency was highly dependant on the level of light falling on the neon.
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Old 12th May 2007, 08:54 AM   #6
Netlist is offline Netlist  Belgium
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Among the many unfounded claims I found at that website, this looks like a very obvious one.
These are the spikes generated by a neon lamp in close proximity of the scope probe, not connected to the circuit. Try that with a LED.

/Hugo
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Old 12th May 2007, 09:05 AM   #7
sandyK is offline sandyK  Australia
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I feel sure that most members would be well aware of the noise from neons,to say nothing of the flickering. A couple of my nice green bezelled rocker switches use neons, and none of them still work. How many extension power
boards have neons that don't flicker , or for that matter still work ?
I did a quick "Google" for "light emitting diode noise" and was unable to find any reference to their noise generation, only noise generated by their control circuitry, as in traffic lights etc. On the contrary, LEDs seem to be used a lot in noise detection equipment !
SandyK
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Old 12th May 2007, 09:27 AM   #8
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There was a thread here a year or so ago where someone actually measured the noise from LEDs, and IIRC, it was insignificant.
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Old 12th May 2007, 11:20 AM   #9
SY is offline SY  United States
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Quote:
Is this guy for real ?
Of course he is. He's also wrong and has no clue as to how to do an experiment, but that does not change his reality. He exists, he occupies space, and has mass no matter how trivial and foolish the things he writes or (maybe) believes.



Quote:
I find it very difficult to believe that a LED , when passing a current of several mA, will respond to external stimulus at any meaningful level.
It doesn't. I've tried measuring it with a flickering high intensity light just inches from the LED and... nothing. Neons are very different, much noisier but have their own peculiar advantages.
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Old 12th May 2007, 11:35 AM   #10
Nordic is offline Nordic  South Africa
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Good reply S.Y... very usefull...

I suppose what kills neons, is the HV spikes they experience several times a day...unlike X and Y caps they are not designed for this and have no selfrepair feature...

What are some of the benefits you alude to?
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