Why even bother doing that? The data all show that, real world, this is an absolute nothing-burger. John's engineering source for the "problem" was a famously unbalanced person with no technical knowledge. If he doesn't want to use them as references in his design, that's fine, but making up pseudo-scientific reasons for not doing so is sheer hucksterism.
Two questions i would like you ask yourself, SY. (And don't think I have my member card of any snake oil party ;-)
- Would-you like to see somebody arguing with you in such a disagreeable way ?
- For some reasons, that I ignore, (every body have his own scales of value) John likes to cut the hairs in four. Concentrating in some details that most of us don't care, considering we have most important things to improve first.
You know, like silver wires in a preamp, or such.
(Well, it is nothing wrong, sliver wires are not an offence against any laws of electricity: they have better conductivity than copper.)
Now, about this LED sensitivity to light (stupid) controversy. Let's be objective.
Are LEDs sensitive to external lights ? Yes. A lot ? Not. Enough to influence the performance of a device and make any difference? You think not, in normal situations (I do either) John thinks yes. What the trouble ?
In fact I have no opinion on this question, because all depends of what we are talking about. A MMC preamplifier, very low level, witch will be amplified a lot, or a VAS ?
Reason why I asked a measurement in real situation: By example, a LED as the CSS reference in a MMC cartridge pre-amplifier. (Witch I don't really care as it is faster to let the LEDs in the dark and forget, than to measure, because no more source of light, no more question.)
People often do. No biggie. Of course, I don't make any money from audio hucksterism, so I may not feel as emotionally invested.
The French term I know involves a fly and certain sexual practices. And it may indeed be an appropriate metaphor.
That is exactly where I use them, and in two different extremely quiet phono stages. Fortunately, I took advice from a competent engineer and not some nontechnical crazy lady I was banging.
OK, time to explain myself further: I don't use LED's as indicator lights because it is difficult to add just one and not unbalance the total DC current in the circuit. As my best circuits use a power supply transformer without using the center tap (why is a separate issue), everything remains balanced with MY circuits because they are designed with complete symmetry and therefore draw just as much current from the positive rail as the negative rail. Adding an LED would typically draw more current from one of the power supply rails and slightly unbalance the current load. Perhaps, it would be OK, perhaps not, but I just avoid the problem by not using one as an external indicator light.
I started this discussion with a '-) when asked about LED's for an indicator light remembering that Enid Lumley had complained about them, many decades ago. SY jumped on me (and Enid, who was a qualified electronic technician and had a MA from UCLA in psychology) because he uses an LED as a bias control at the INPUT of a phono stage (quite a sensitive place I should think, about 100,000 times more sensitive than an indicator light) and he took to showing where I was wrong.
Actually, just a few weeks earlier, I was talking to Walt Jung about LED's and he told me that red LED's were very quiet. (I never measured one for noise) So, my '-) that included Enid Lumley (RIP) probably created unnecessary controversy, yet in further investigations it was found that LED's could be modulated by external light sources, even when forward biased. Personally, if I were to use an LED in a critical section of a circuit, I would protect it from light, somehow, perhaps with heat shrink. Better safe than noisy! '-)
I started this discussion with a '-) when asked about LED's for an indicator light remembering that Enid Lumley had complained about them, many decades ago. SY jumped on me (and Enid, who was a qualified electronic technician and had a MA from UCLA in psychology) because he uses an LED as a bias control at the INPUT of a phono stage (quite a sensitive place I should think, about 100,000 times more sensitive than an indicator light) and he took to showing where I was wrong.
Actually, just a few weeks earlier, I was talking to Walt Jung about LED's and he told me that red LED's were very quiet. (I never measured one for noise) So, my '-) that included Enid Lumley (RIP) probably created unnecessary controversy, yet in further investigations it was found that LED's could be modulated by external light sources, even when forward biased. Personally, if I were to use an LED in a critical section of a circuit, I would protect it from light, somehow, perhaps with heat shrink. Better safe than noisy! '-)
"si quis vestrum, iudices, aut eorum qui adsunt..."
I will do something surrealistic, now, take the defense of Mr. John Curl.
(Please John, don't read what follows, pure ad hominem)
When I arrived in this Forum, I was absolutely shocked by some J.C posts. You knows, those about burning silver cables, marking their sens (source-> charge), and all those Bybee bottles of oil...
And sometimes exasperated by the self-promoting and arrogant tone of some of its interventions.
I knew his name, for the work he did on the very innovative and original PA system of a famous (at this time) Rock'nroll group. And because he was one of the designers of some professional tape recorders I used often in studios.
How can he be so far from the modest and didactic attitude we can expect from a famous and technically flawless expert ? Like are oncle Nelson and brother Bob ;-).
I immediately joined the benches of the civil party and the accusers.
With time, slowly I changed position, and here I am, sitting at the defense table.
What i first thought was arrogance, I'm sure now it is just an enormous lack of self confidence.
What I first thought was dishonesty (snake oil promotion), I'm sure now it is deep uncertainty. That I can understand because, in a way, I share this uncertainty. And I had to suffer here, like him, of the violent attacks from those I call "Objectivists", because we are not sure that measurements can reflect everything that we can "feel". And that, as him, I spend a lot of time in listening.
It seems that John likes to live in some kind an imaginary world, where magic has an important part. More than for most of us. Magic is always an attempt to answer real questions. For what i know about the work he did, nothing that offense the laws of electronic morality.
Of course, he knows a lot about electronic for audio. Read a lot, experimented a lot. Of course he made measurements, and know what they mean. It is not enough for him. Are we going to tie him to the stake for witchcraft ?
After all, we all have our own imaginary world... Even the ayatollah of "objectivism" that believe in the magic of pure numbers.
My client has a certain age, my client has achieved a lot in his life, which were considered by many as exceptional. This deserves acquittal and respect. And even admiration. Can't we feel a trace of jealousy in this JC bashing ?
For what remains, a little indulgence, a smile, a nice tune when some points could lead beginners on track that seems wrong for most of us... seems to me large enough. And only "point of views".
It is time to treat the wounded of this battle of the LED, no one knows why it started. And to treat John as a friend, sometimes a little original, but still interesting to have at his table. And, who knows, learn sometimes things from him ?
I will do something surrealistic, now, take the defense of Mr. John Curl.
(Please John, don't read what follows, pure ad hominem)
When I arrived in this Forum, I was absolutely shocked by some J.C posts. You knows, those about burning silver cables, marking their sens (source-> charge), and all those Bybee bottles of oil...
And sometimes exasperated by the self-promoting and arrogant tone of some of its interventions.
I knew his name, for the work he did on the very innovative and original PA system of a famous (at this time) Rock'nroll group. And because he was one of the designers of some professional tape recorders I used often in studios.
How can he be so far from the modest and didactic attitude we can expect from a famous and technically flawless expert ? Like are oncle Nelson and brother Bob ;-).
I immediately joined the benches of the civil party and the accusers.
With time, slowly I changed position, and here I am, sitting at the defense table.
What i first thought was arrogance, I'm sure now it is just an enormous lack of self confidence.
What I first thought was dishonesty (snake oil promotion), I'm sure now it is deep uncertainty. That I can understand because, in a way, I share this uncertainty. And I had to suffer here, like him, of the violent attacks from those I call "Objectivists", because we are not sure that measurements can reflect everything that we can "feel". And that, as him, I spend a lot of time in listening.
It seems that John likes to live in some kind an imaginary world, where magic has an important part. More than for most of us. Magic is always an attempt to answer real questions. For what i know about the work he did, nothing that offense the laws of electronic morality.
Of course, he knows a lot about electronic for audio. Read a lot, experimented a lot. Of course he made measurements, and know what they mean. It is not enough for him. Are we going to tie him to the stake for witchcraft ?
After all, we all have our own imaginary world... Even the ayatollah of "objectivism" that believe in the magic of pure numbers.
My client has a certain age, my client has achieved a lot in his life, which were considered by many as exceptional. This deserves acquittal and respect. And even admiration. Can't we feel a trace of jealousy in this JC bashing ?
For what remains, a little indulgence, a smile, a nice tune when some points could lead beginners on track that seems wrong for most of us... seems to me large enough. And only "point of views".
It is time to treat the wounded of this battle of the LED, no one knows why it started. And to treat John as a friend, sometimes a little original, but still interesting to have at his table. And, who knows, learn sometimes things from him ?
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That's why it's particularly sad when he goes out of his way to promote nonsense.
John, you could connect the indicator led between +V and -V rail, instead of +V and GND, but then, you could "unbalance" left and right channel power supply ;-)
I like to read this thread, one could read something interesting but every 100 pages, or more...
It would be more fun (IMO) if SY could restrain his character and don`t jump on every opinion. I don`t know what is he doing here, because he knows everything about everything and already designed the perfect sound system for him
I like to read this thread, one could read something interesting but every 100 pages, or more...
It would be more fun (IMO) if SY could restrain his character and don`t jump on every opinion. I don`t know what is he doing here, because he knows everything about everything and already designed the perfect sound system for him
On my opinion, it is not "non sense", and I don't see where can be "promotion".
Questions are:
-Are LEDs less noisy than Zeners ?
-Are LEDs more accurate as voltage references (temperature, dispersion, current dependency etc.)
Well, it has been said that LEDs are sensible to external light. Right, they are:
-How much for our purpose ?
-How can-we get rid of this flaw, if exists ? (This answer kills the previous)
Five lines to say everything about this subject ? Not a disagreeable word for nobody.
And we could spend our efforts to measure and compare various kind of LEDs.
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Is it better not to be a gentleman and base technology on faith or scepticism ?
Jacco, I believe an important part of this controversy is based on something amusing, on my point of view. LEDs are designed to be light generators. using them as voltage references is somewhere 'illegal', it is a function creep, if you see what I mean
;-)
By the way, no semiconductor provider has had the idea of encapsulating LEDs in an opaque enclosure and add them to his catalog of Zeners ?
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Not really function creep, but imo a happy coincidence.
The first time I saw a red LED used in a temp-compensated current generator was an application note from the now-absorbed Precision Monolithics. It simply asserted that the tempco of forward voltage was a good match for a silicon bipolar's b-e junction, without any references.
Gallium Arsenide Phosphide and related compounds took a lot of work to get to where there were good yields for making LEDs. One could conjecture that the purity and other details of the processing required for uniform light output were as well beneficial to the electrical properties such as noise, and fidelity to a given I-V curve.
Since it is very unlikely that silicon integrated circuits will use LEDs on chip, and since there are other ways to produce temperature-compensated current generators in silicon, the realm of mixing LEDs with other components will remain the province of some amount of discrete components in the system.
So they will remain useful, but somewhat problematic for production as there is really no manufacturer's guarantee about their suitability. An anecdote here: when I used one for a level shifting circuit for an OEM automotive amplifier, when I'd foolishly backed myself into a corner by quoting a cost of a change before having the whole specification, I had the purchasing agent looking for parts. She was a dear person and a hard bargainer, but not too swift technically.
She had a stream of reps coming through, pitching their wares as indicator lamps, and assuring the superiority of one of them over some other one from the competition. I had a hell of a time getting them to understand that it was not an indicator lamp, and that I needed the so-called "standard red" and didn't care at all about the luminous efficacy.
I have a distant recollection of something along those lines. But it should be recalled that they do not have the sharp knee of zeners, and it would be inappropriate to refer to them as such. Their appeal is due to (1) the low noise as a forward-biased diode, and (2) the reasonable match of their temperature coefficient of forward drop at a given current to the roughly -2.2mV/degree Kelvin of a silicon bipolar Vbe.
Yes. I think they were the ones who had a very odd advertising campaign with an audio focus, and one of the ads made it to semi-permanent posting on the walls of a lab at Harman. It asked "Are you an Audio Silicon Specialist?
Seen the ad, not the poster.
Right up my back alley.
(ox-aleph-alpha. as opposed to beta)
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Yes, significantly.
It depends, but for audio work, no significant difference.
Close to zero.
For the purpose of audio, it doesn't. If you want to do something for the sake of doing something, feel free, but making silly claims is... well, silly.
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