Yes, there are some people who need to believe that proper engineering is missing something so they will buy into almost anything which is different and is accompanied by a good story. I am not saying the OP fits into this category, as I suspect he is simply a punter who spent some money and then heard a change which he believed to be an improvement. I find it interesting that some of the LDR volume vendors are happy to admit here that their product may slightly distort the signal, yet in a pleasant way - I guess this doesn't appear in their advertising or comments to magazines?xnor said:
Thank you for that Andrew. That's truly wonderful to know.
I'll keep it in mind when I listen to some music today.
Yes, I suppose it is merely a matter of perception and perspective that the things I mentioned hearing in the music are an improvement or not.
Of course speaking from experience
with using LDR's as attenuators in your ownaudio system.
Perhaps when that occurs, we might pay more attention.
Cheers / Chris
Why would I choose to use a known nonlinear resistor as a volume control? Why do you think I need to experience something in order to know about its weaknesses?Chris Daly said:
For example, I have never put diesel fuel in my petrol car. Does that mean that I cannot advise someone else not to do it, as I have no personal experience of the negative consequences? One of the big advances in civilisation was when writing was invented, which means that people can easily learn from other peoples' experiences instead of having to try everything for themselves.
I understand that LDRs are nonlinear; I haven't measured them myself but people who know about them (including some LDR volume control vendors) say that this is so. I therefore know that they will distort a music signal.
A device which is basically symmetric and in a symmetric circuit situation can only produce odd order distortion, because only odd order distortion is symmetric. To get even order distortion you need an asymmetric device or a DC bias. Given that an LDR is basically just a film of cadmium sulphide with electrodes attached I would expect it to be symmetric in its electrical response. This assumes that the electrodes are basically the same at each end.stvnharr said:
I didn't change your word. I used your word: "perception". It is the correct word to use.
Well, this has been fun, not.
The only worthwhile information to take from the OP's first post is that he bought an LDR-based preamp and is pleased with his purchase and now understands why the people who use LDR equipment praise it. Everything else is an exerecise in interpretation, quibbling over adjectives, and challenging the poster's right to express his opinion.
It seems that most people fit into one of three major groups of people on this earth when it comes opinions on LDRs:
1. People who don't care.
2. People who have listened to them and have an informed opinion which is almost invariably positive to some degree or another.
3. People who haven't listened to them and thus don't know what they sound like and have established an opinion based on rather sketchy technical information.
This argument smacks of the transistor-tube arguments of the 1960s and 1970s and the later truly "bizarre"(!) suggestion that some people made that vinyl was somehow better than "perfect" CDs. In these cases people could hear the difference long before anyone could explain why it was so, and since the facts ran counter to logic they were pooh-poohed for a long time. I don't think anyone would disagree at this point that tube equipment and vinyl have merit and can sound remarkably good.
If a person's mind is made up about how something sounds without ever personally listening to it, it's too bad but let's not waste time arguing. My uneducated opinion is that what matters is how it sounds, everything else about LDRs might be interesting, but that's all.
If you have an open mind and are convinced you can confirm your opinion that LDRs are destructive to good sound, then find someone nearby who has a set and go listen -- you can feel good later that you confirmed your earlier informed opinion. And, if you go with an open mind, be prepared for the remote possibility that the people who do listen through LDRs might -- as a large and growing group -- know something that you don't.
The only worthwhile information to take from the OP's first post is that he bought an LDR-based preamp and is pleased with his purchase and now understands why the people who use LDR equipment praise it. Everything else is an exerecise in interpretation, quibbling over adjectives, and challenging the poster's right to express his opinion.
It seems that most people fit into one of three major groups of people on this earth when it comes opinions on LDRs:
1. People who don't care.
2. People who have listened to them and have an informed opinion which is almost invariably positive to some degree or another.
3. People who haven't listened to them and thus don't know what they sound like and have established an opinion based on rather sketchy technical information.
This argument smacks of the transistor-tube arguments of the 1960s and 1970s and the later truly "bizarre"(!) suggestion that some people made that vinyl was somehow better than "perfect" CDs. In these cases people could hear the difference long before anyone could explain why it was so, and since the facts ran counter to logic they were pooh-poohed for a long time. I don't think anyone would disagree at this point that tube equipment and vinyl have merit and can sound remarkably good.
If a person's mind is made up about how something sounds without ever personally listening to it, it's too bad but let's not waste time arguing. My uneducated opinion is that what matters is how it sounds, everything else about LDRs might be interesting, but that's all.
If you have an open mind and are convinced you can confirm your opinion that LDRs are destructive to good sound, then find someone nearby who has a set and go listen -- you can feel good later that you confirmed your earlier informed opinion. And, if you go with an open mind, be prepared for the remote possibility that the people who do listen through LDRs might -- as a large and growing group -- know something that you don't.
Okay then, you used the word "perception" out of the context in which it was written to further your point of view.
If I read you correctly, and I'm certain that you will correct me if I am in error, you view the low amounts of low order distortion as a minor signal degeneration, rather than just an artifact of the signal as it goes through the LDR material.
You perceive the minor signal degeneration as a major fault.
I wrote earlier, in Post #81, that I was unable to hear any artifact of the harmonic distortion profile created in the music signals by the LDR material and found the minor signal degeneration to be irrelevant.
Thank you.
Only one little quibble is that I didn't buy a preamp. I bought some parts and put them together in a diy project as described here:
http://www.diyaudio.com/forums/analog-line-level/281859-tortuga-ldr-preamp-build.html
Well, there's not much else to do. You've offered no supporting data, not even the most rudimentary. You've not done any ears-only testing. What is offered is... "I say so and I have testimonials."
This is a technical forum. If you want to market to people happy to accept claims with no backup if the story is good enough, there are better places to do so. If you post product promotion here, expect technical questions and be prepared to answer them on a technical basis.
Because experience gives you credibility, without it you are inviting inaccuracy
and other persons misinformation and even superstition.
Given your expertise in other areas of electronics, it would be a relief to us all,
for your actual experience with LDR's, to replace guessing.
Cheers / Chris
That's nonsense. Go back a few pages and read, e.g. this or this.
Yeah, like with like magic bracelets. The main difference with LDRs is that they can actually have a real distorting effect. Here are CaptainWatt's words: "[...] and yes they've less that pristine specs regarding distortion".
That doesn't invalidate anyone's opinion or preference for distortion...
Like this or this (some measurements by Nelson Pass) and info from the datasheets?
What I am surprised about is that there doesn't seem to be any interest in a systematic investigation in what is going on (the truth(tm)) and approach in improving one's system by type 2 people.
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There is by the quotes in your post, confirmation of
distortion being very low with LDR's, and affirmed by
the manufacturers with similar, if not identical figures.
There is continual interest in improving audio results with LDR's,
for instance post #63 on this thread, where I provided some insight
into how to get even better result with them.
Stvnharr has I think simply tried to tell us about his audio impressions,
and by all accounts they are very similar with those who happen to
already use NSL32SR2(S) and NSL32SR3 audio coupling LDR's
Cheers / Chris
Has anyone done this? All we have said is that his opinion is mistaken. Nobody has try to forbid him from saying whatever he wishes to say.wapo54001 said:
LDR volume controls distort the signal. That is a fact which even some LDR vendors admit. The issue then is how much they distort and the extent to which this is audible. A further issue is whether some people like the distortion - anecdotal evidence suggests that they do. To go from that to 'LDR volume controls damage the signal less than conventional resistors' is simply wrong.
Where are you reading this?
It's magnitudes higher distortion than conventional solutions, the distortion changes with the signal, changes with impedance and will therefore be different for any LDR.
"they've less than pristine specs regarding distortion".
Nope, where?
At least one preamp manufacturer affirmed the opposite, that "they've less than pristine specs regarding distortion".
I think you missed my point. I was talking about the reasons to use LDRs in the first place and investigating the claims about their "sound" (which an attenuator should not have anyway) systematically.
I'm sure you can tune LDR circuits to reduce nonlinearity or match impedances, improve stability, reduce distortion etc. but that kinda proves the point above.
See #115.
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was preceded by:
The first comment is bluster, the second untrue. (Who, by the way, is "we"?)
You started (true to form - we've argued before) with psycho-babble served with a dash of ad hominem - "there are some people who need to believe that proper engineering is missing something so they will buy into almost anything which is different and is accompanied by a good story". Etc. etc. You add that:
From there, you hint that passing (but uncited) remarks by designers are an adequate substitute for proper data. They're not. Next, you brag that even listening to the devices in question is beneath you as you ". . . know that they will distort a music signal".
Don't we all? Looking to "proper engineering" for a moment, I've just dug out a pertinent Silonex app note, "Audio level control with resistive optocouplers". It notes that LDR distortion performance is "medium to good" but qualifies that by adding that, though highish at the extremes:
Though my guess is that designers who use LDRs would dispute none of these and other points in the paper, the data it offers seem to suggest that your comments are so over-simplified as to verge on crass.
Proper engineering further tells us that stepped attenuators also distort the signal with different resistor types and switxch designs doing so in different ways and that rotary pots, even good-quality ones, are often much worse. (Comparative data are hard to come by.) Whether listeners are more tolerant of the sound of SA or rotary pot distortions compared to those of LDRs is a proper topic for debate but I find your approach, which has something of the bully about it, most unhelpful.
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