Today Veritasium posted an excellent video covering the history and theory of Blue LEDs, it is absolutely worth watching. 👍
olen
olen
Have not seen the video, but always hated blue leds. Cold and heartless on audio equipment.
In June of 2015 I mentioned the outstanding achievement the creation of the blue LED was, but it did not generate any reaction.
https://www.diyaudio.com/community/threads/the-diyaudio-firstwatt-f6.258613/page-36#post-4374290
https://www.diyaudio.com/community/threads/the-diyaudio-firstwatt-f6.258613/page-36#post-4374290
Blasphemy! 😆
Personal preferences aside you will enjoy the excellent story which is well told.
Silicon Carbide blue LEDs had a brief vogue before GaN LEDs kicked them to the curb. Cree (always looking for a way to leverage their SiC expertise) and Liteon were two vendors pushing SiC blue LEDs for a brief time.
The light from SiC LEDs is a more soothing "sky blue" than the actinic blue output of GaN LEDs. What clinched the sad fate of SiC blue leds was their high voltage drop and less than stellar efficiency. 10 mA through a SiC blue LED gets you to "pilot light" intensity, whereas that same current through a GaN LED will get you to a brightness level that will just about poke holes in your retina. One of the surplus vendors I used to frequent had a stock of the old SiC blue leds. I grabbed a bunch, as I find them far more aesthetically appealing than the GaN flavor.
The light from SiC LEDs is a more soothing "sky blue" than the actinic blue output of GaN LEDs. What clinched the sad fate of SiC blue leds was their high voltage drop and less than stellar efficiency. 10 mA through a SiC blue LED gets you to "pilot light" intensity, whereas that same current through a GaN LED will get you to a brightness level that will just about poke holes in your retina. One of the surplus vendors I used to frequent had a stock of the old SiC blue leds. I grabbed a bunch, as I find them far more aesthetically appealing than the GaN flavor.
I have uses for obsolete LEDs, mostly as quiet voltage references. The old GaAsP deep-red LEDs make a dandy 1.6V reference with 10-20mA of bias current. The wishy-washy yellow green GaP "green" LEDs give you around 2V at the same bias level. GaN LEDs are apparently a bit on the noisy side...
There is a thread floating around DIyaudio discussing the use of of LEDs as voltage references, with measurements of voltage drop and noise level.
the thread is here
https://www.diyaudio.com/community/threads/some-noise-measurements-for-leds-and-zener-diodes.35821/
There is a thread floating around DIyaudio discussing the use of of LEDs as voltage references, with measurements of voltage drop and noise level.
the thread is here
https://www.diyaudio.com/community/threads/some-noise-measurements-for-leds-and-zener-diodes.35821/
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The green led in the middle looks to be a GaN green led, with an output more "pure green" than the old standard GaP led, which was more of a yellow-green. It wasn't "easy" to get a pure green LED until GaN came along.
Funny to relate - all LEDs depend on availability of Gallium, as it ends up in the formulation some way or the other. The dance started with GaAs, continued with GaAsP and GaP, GaAlAs, and finally the highly efficient GaN, which enabled LED lighting. The current "white" LEDs used in lighting are blue GaN LEDs with a neodymium-based yellow conversion phosphor piled on top. The white light you think you see is a combination of blue and yellow.
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When I got my Aleph 5, about 20 years ago, I replaced the indicator LED to improve its appearance and believe have done so again since. I'm now quite tired of the ubiquitous blue LEDs that almost everything has nowadays, which are ~460nm, but I still love the more purple-hued versions at ~430nm. Ayre Acoustics (and Pass Labs lit meters, come to think of it!) has or used to have an LED indicator about this color. I found a really nice one, a Bivar 3BWD-S to use on the front of my F5 build and it's still available.
Also, there was a fairly recent story of how Dan D'Agostino got the industry onto blue LEDs, but I can't remember where or I'd post the link. The gist is that Krell was located next to an industrial user of very expensive blue LEDs, which had a very high failure rate unrelated to the cosmetics of the light. Dan offered to buy all the surplus "failures" to use as indicators if he was given exclusive access to them at an "affordable" price. The rest is history, though it helped that costs and technology made it happen mainstream.
Also, there was a fairly recent story of how Dan D'Agostino got the industry onto blue LEDs, but I can't remember where or I'd post the link. The gist is that Krell was located next to an industrial user of very expensive blue LEDs, which had a very high failure rate unrelated to the cosmetics of the light. Dan offered to buy all the surplus "failures" to use as indicators if he was given exclusive access to them at an "affordable" price. The rest is history, though it helped that costs and technology made it happen mainstream.
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Walt Jung has a fairly recent paper about the suitability of various LEDs as references, posted in the refsnregs directory at https://mirror.waltjung.org/.
Thanks for this post, Olen. Made my day.
I am in awe of Mr. Nakamura. You are an inspiration, sir. (as if he will see my post)
I would never buy a product from NICHIA if I can help it. Despicable disgusting behavior.
No surprise that bastards exist all over the world.
I am in awe of Mr. Nakamura. You are an inspiration, sir. (as if he will see my post)
I would never buy a product from NICHIA if I can help it. Despicable disgusting behavior.
No surprise that bastards exist all over the world.
I remember when I was excited to buy a blue LED for $10 way back when the earth was flat!
After my dad got some surplus yellow LEDs, I remember him saying we were awaiting the blue LED, and it would kick off a new era of display panels and really efficient lights.
I also remember the dashboard of 85-86 VWs having this array of LEDs, but the high-beam blue must not have been a LED, in ~1984?
I also remember the dashboard of 85-86 VWs having this array of LEDs, but the high-beam blue must not have been a LED, in ~1984?
