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Post by dsjr on Jun 13, 2019 6:35:42 GMT
But all they are is a resistor in series and a resistor across the load are they not? A simple film pot will do that with far less measurable distortion and better tracking over most of it's range - NO messing around with complex power supplies either to add more 'mess.'
LDR's had a stinking rep for non-linearity and even if they're fine when new, I understand they go off over time when used this way. Why over-complicate something that can be done very simply if a 'passive' attenuator is all you need?
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Post by macca on Jun 13, 2019 6:50:01 GMT
To resurrect an old thread, I have recently started to look further into the merits (or not) of LDR's and came across this article (again)
www.neurochrome.com/tortuga-audio-ldr3/
Chris has again stated that his LDR Pre's are distortion free and that the poor performance of the LDR's (Tortuga's unit) is down to poor circuit implementation.
I have suggested he should send one of his units to the forum that tests kit for free, but I can't recall the name of it. Can anyone remember? I think Dave highlighted them before. Audio Science Review - www.audiosciencereview.com/forum/index.php |
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Post by Deleted on Jun 13, 2019 10:05:40 GMT
To resurrect an old thread, I have recently started to look further into the merits (or not) of LDR's and came across this article (again)
www.neurochrome.com/tortuga-audio-ldr3/
Chris has again stated that his LDR Pre's are distortion free and that the poor performance of the LDR's (Tortuga's unit) is down to poor circuit implementation.
I have suggested he should send one of his units to the forum that tests kit for free, but I can't recall the name of it. Can anyone remember? I think Dave highlighted them before. Audio Science Review - www.audiosciencereview.com/forum/index.phpThat's the One! Thanks Macca.
According to the forum, there is a LDR Stereo Coffee due there. We await the results with gusto!
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Post by Deleted on Jun 13, 2019 11:03:01 GMT
Haven't they've been waiting for the LDR for some time? Surely if it was as good as claimed, it would have been made available pretty sharpish to counter the bad reviews.......?
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Post by macca on Jun 13, 2019 11:24:15 GMT
It's got to get from New Zealand to Washington State, maybe that's taking a while?
I already compared all these LDR pre-amps years ago so I know which is best.
Like most components they have strengths and weaknesses. The 'drifting' thing is solved albeit in different ways. The distortion is moot since any active pre-amp or buffer will have some distortion.
Don't really understand why ardent subjectivists who say they are only concerned with 'what it sounds like' are suddenly keen on seeing distortion measurements when it comes to LDR pre-amps but there you go.
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Post by dsjr on Jun 13, 2019 12:58:17 GMT
A resistor L pad shouldn't have any distortion at all to be fair and the 'sound' from the output should be identical to that going in if levels are matched precisely and impedances don't mismatch. The fact you lot claim you can 'hear' when one of these is put in the circuit, surely means it's distorting audibly? - and that means HIGH distortion. I'll stick to me old 'cookers' which still 'measure' very well and don't get in the way of reverb tails or instrumental timbres into various power amps  |
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Post by Deleted on Jun 13, 2019 14:15:47 GMT
It's got to get from New Zealand to Washington State, maybe that's taking a while? I already compared all these LDR pre-amps years ago so I know which is best. Like most components they have strengths and weaknesses. The 'drifting' thing is solved albeit in different ways. The distortion is moot since any active pre-amp or buffer will have some distortion. Don't really understand why ardent subjectivists who say they are only concerned with 'what it sounds like' are suddenly keen on seeing distortion measurements when it comes to LDR pre-amps but there you go. It's not a case of judging its performance based on measurements, it's a case of proving the claims of the designer, which as of yet hasn't been done. Like I said before, how something measures isn't the final word in performance but when you keep claiming that LDRs pres measure better than any other type, you MUST provide evidence to back it up. Personally, if It was mine and I was as confident as the designer is, it would be top of my priority list to prove it. I have no issue with the subjective review, we all do that. |
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Post by macca on Jun 13, 2019 15:35:33 GMT
A resistor L pad shouldn't have any distortion at all to be fair and the 'sound' from the output should be identical to that going in if levels are matched precisely and impedances don't mismatch. The fact you lot claim you can 'hear' when one of these is put in the circuit, surely means it's distorting audibly? - and that means HIGH distortion. I'll stick to me old 'cookers' which still 'measure' very well and don't get in the way of reverb tails or instrumental timbres into various power amps Who is 'you lot' and what is being put in circuit? |
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Post by Deleted on Jun 13, 2019 15:39:49 GMT
A resistor L pad shouldn't have any distortion at all Sorry, no, a single resistor will add distortion, some more than others, its measurable (with care) and often documented in the spec sheets under "voltage coefficient of resistance". As to is it can be heard, that a a different matter, but the "resistors don't distort" ship has sailed long ago, |
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Post by dsjr on Jun 13, 2019 18:05:28 GMT
Well, all active preamps are full of the sodding things, the more exalted with often even more inside, so with respect, if it really mattered audibly....... I'm probably wrong though and as I'm not in a position to measure such things, I can't dispute with those who have. Oh alright, I'm maybe going deaf with too much loud rock music in my past When you see how good DACs are today though (and they're full of chips as well as conventional passive components), it makes the likes of me look at some of these things differently when an LDR preamp measures about as badly as a typical domestic solid state amplifier if ASR is to be believed (digging hole ever deeper - apologies - I'll shut up now). |
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Post by Deleted on Jun 13, 2019 18:51:56 GMT
A resistor L pad shouldn't have any distortion at all Sorry, no, a single resistor will add distortion, some more than others, its measurable (with care) and often documented in the spec sheets under "voltage coefficient of resistance". As to is it can be heard, that a a different matter, but the "resistors don't distort" ship has sailed long ago, Solid info, thanks Nick. SO if LDRs distort, Resistors distort, TVC ring and the chinese relays seem to go out of step in terms of channel balance, which is the least of the evils? |
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Post by sq225917 on Jun 13, 2019 19:25:56 GMT
Assuming all the rights impedances and plenty of drive a passive pre will introduce the least to the signal. But in the real world having a buffer in there is sensible in a mixed make system.
I've just taken receipt of that TKD pot today, not bad at all, channel matching better than 1% across the range, that'll do for me.
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Post by Deleted on Jun 13, 2019 22:29:26 GMT
Assuming all the rights impedances and plenty of drive a passive pre will introduce the least to the signal. But in the real world having a buffer in there is sensible in a mixed make system. I've just taken receipt of that TKD pot today, not bad at all, channel matching better than 1% across the range, that'll do for me. Thanks Si. Hope it sounds as acceptable. |
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Post by Deleted on Jun 13, 2019 22:40:42 GMT
Sorry, no, a single resistor will add distortion, some more than others, its measurable (with care) and often documented in the spec sheets under "voltage coefficient of resistance". As to is it can be heard, that a a different matter, but the "resistors don't distort" ship has sailed long ago, Solid info, thanks Nick. SO if LDRs distort, Resistors distort, TVC ring and the chinese relays seem to go out of step in terms of channel balance, which is the least of the evils? Well my point was that resistor do generate measurable distortion. But it is very small. I was just responding to the suggestion that it was zero. What is interesting though, is that despite the distortion being at a level that should not matter, and only in the last 10 years or so can be measured, the resistors that generally are preferred over the years are the ones with low distortion. So even though it wasn't measured, and so low that it should not matter, people still seemed to tell them apart. LDR's are just flat out non linear. I have no issue (or business having a view) that folk like them, but they are non linear, they are not passive resistors (despite the name) they are semiconductors that vary their resistance when hit by photons. |
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Post by Deleted on Jun 14, 2019 10:01:25 GMT
Solid info, thanks Nick. SO if LDRs distort, Resistors distort, TVC ring and the chinese relays seem to go out of step in terms of channel balance, which is the least of the evils? Well my point was that resistor do generate measurable distortion. But it is very small. I was just responding to the suggestion that it was zero. What is interesting though, is that despite the distortion being at a level that should not matter, and only in the last 10 years or so can be measured, the resistors that generally are preferred over the years are the ones with low distortion. So even though it wasn't measured, and so low that it should not matter, people still seemed to tell them apart.
LDR's are just flat out non linear. I have no issue (or business having a view) that folk like them, but they are non linear, they are not passive resistors (despite the name) they are semiconductors that vary their resistance when hit by photons. That IS very interesting. SO there may be hope for those of us who claim the odd boutique parts we fit "do/can" make a difference  The LDR type preamps that were here certainly didn't sound bad and Chris of Stereo Coffee has said he'll send me an optimised one to try so with all of that and with the upcoming ASR tests, we should get a pretty good idea of where this thing really sits. |
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Post by Deleted on Jun 14, 2019 10:21:33 GMT
Well my point was that resistor do generate measurable distortion. But it is very small. I was just responding to the suggestion that it was zero. What is interesting though, is that despite the distortion being at a level that should not matter, and only in the last 10 years or so can be measured, the resistors that generally are preferred over the years are the ones with low distortion. So even though it wasn't measured, and so low that it should not matter, people still seemed to tell them apart.
LDR's are just flat out non linear. I have no issue (or business having a view) that folk like them, but they are non linear, they are not passive resistors (despite the name) they are semiconductors that vary their resistance when hit by photons. That IS very interesting. SO there may be hope for those of us who claim the odd boutique parts we fit "do/can" make a difference The LDR type preamps that were here certainly didn't sound bad and Chris of Stereo Coffee has said he'll send me an optimised one to try so with all of that and with the upcoming ASR tests, we should get a pretty good idea of where this thing really sits.
IMO, LDR type preamps (well at least the ones I have seen) sound good because of the distortion not despite it. But I have not seen, heard or measured all of them, But I do feel they are a solution in search of a problem.
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Post by Deleted on Jun 14, 2019 12:37:52 GMT
I will read that. Thanks.
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Post by Deleted on Jun 14, 2019 18:07:24 GMT
I experimented with a Stereo Coffee LDR passive pre a couple of years ago and it was a disaster. Money down the drain. I bought an eBay kit but could not get it to work. I think the main problem was that assembly instructions were so lacking in punctuation and had sentences that were so poorly constructed, it was impossible to work it all out. This lead me to sending the kit back to Chris which is bloody expensive, UK to New Zealand. It ended up with Chris building me a Stereo Coffee into a Chinese chassis which finally worked but the necessary engineering on the chassis was very diy shoddy so it didn’t look good. Also, in my system, it sounded awful. Very sharp, glassy edged and bright. That’s not just my impression. Two of my mates were with me when we tried it and they are reliably hearing audiophiles. Now I have heard of others who have been very satisfied with their Stereo Coffee pre’s but they are not for me, and personally, regardless of the likes of others, I don’t think they really work properly. If you have a ‘right’ system to start with, this may be why I don’t rate them and others (who might not have a ‘right’ system) do.
A couple of things. These LDR Pre’s are marketed as the equivalent to a pot in a box passive. They are not passive. The Stereo Coffee has considerable gain. The other thing to consider is the overall legality. It was a Bee in his bonnet issue for RD, but overall, I don’t think he was wrong. As supplied, my take is the SC does not conform to EU legislation, and whilst that may not be too much of an issue if you purchase and use, it does become significant if you choose to move the SC Pre on, and that includes disposable at your local authority tip.
I recommend giving this some thought before committing to any LDR based product.
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Post by Deleted on Jun 14, 2019 18:24:57 GMT
I experimented with a Stereo Coffee LDR passive pre a couple of years ago and it was a disaster. Money down the drain. I bought an eBay kit but could not get it to work. I think the main problem was that assembly instructions were so lacking in punctuation and had sentences that were so poorly constructed, it was impossible to work it all out. This lead me to sending the kit back to Chris which is bloody expensive, UK to New Zealand. It ended up with Chris building me a Stereo Coffee into a Chinese chassis which finally worked but the necessary engineering on the chassis was very diy shoddy so it didn’t look good. Also, in my system, it sounded awful. Very sharp, glassy edged and bright. That’s not just my impression. Two of my mates were with me when we tried it and they are reliably hearing audiophiles. Now I have heard of others who have been very satisfied with their Stereo Coffee pre’s but they are not for me, and personally, regardless of the likes of others, I don’t think they really work properly. If you have a ‘right’ system to start with, this may be why I don’t rate them and others (who might not have a ‘right’ system) do. A couple of things. These LDR Pre’s are marketed as the equivalent to a pot in a box passive. They are not passive. The Stereo Coffee has considerable gain. The other thing to consider is the overall legality. It was a Bee in his bonnet issue for RD, but overall, I don’t think he was wrong. As supplied, my take is the SC does not conform to EU legislation, and whilst that may not be too much of an issue if you purchase and use, it does become significant if you choose to move the SC Pre on, and that includes disposable at your local authority tip. I recommend giving this some thought before committing to any LDR based product. One of the things that Alan did comment on at quite some length, was the instructions being a little confusing. I know he sought clarification on them and also noted that he couldn't get the volume to reduce to inaudible. I believe Chris has a fix for that but it required more work than Alan had priced for so it wasn't tried.
As to the fit and finish of your unit, I can't comment as I didn't see it. I did see the boards that Alan was sent and yes, they definitely had a DIY vibe about them due to them being basically breadboard, but I believe this is because the design is constantly evolving, so that is understandable.
Personally, I have no issue with folks buying anything and enjoying it thoroughly. As to whether the units are illegal in the UK, I will leave that to others who are better placed to comment. That said, I did receive a phone call from a forumite to strongly dissuade me from messing with LDRs due to their Cadmium content. I won't be messing with them.
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Post by Deleted on Jun 14, 2019 18:39:54 GMT
It’s the Cadmium which is the issue.
I’m going back about three years on my experience so things might have changed. Still wouldn’t get me to play with an LDR pre again though.
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Post by dsjr on Jun 14, 2019 19:05:30 GMT
If the lcd preamp had gain input to output so the output was louder, there must be a buffer stage inside surely? An 'L-pad' style attenuator can do just that - progressively attenuate?
Seriously confused now (nowt new there then).
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Post by Deleted on Jun 14, 2019 19:59:57 GMT
If the lcd preamp had gain input to output so the output was louder, there must be a buffer stage inside surely? An 'L-pad' style attenuator can do just that - progressively attenuate? Seriously confused now (nowt new there then). Not as confused as me lol |
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Post by Deleted on Jun 14, 2019 20:17:51 GMT
How does that work then? It’s just a light controller resistor isn’t it? The power goes to the light which activates the resistor which attenuates the signal... the pot controls the light?
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Post by Deleted on Jun 14, 2019 21:36:32 GMT
Sorry Guys, I can’t help with the electronic physics, but for sure the Stereo Coffee had gain. The very reason I was exploring it at the time was because aI was at the time looking for a pre amp with no gain. Things have changed now and it is no longer an issue for me.
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Post by Deleted on Jun 14, 2019 21:46:33 GMT
I experimented with a Stereo Coffee LDR passive pre a couple of years ago and it was a disaster. Money down the drain. Also, in my system, it sounded awful. Very sharp, glassy edged and bright. That’s not just my impression. Two of my mates were with me when we tried it and they are reliably hearing audiophiles. interesting, but the polar opposite from my experiences with one. guess it shows how system dependent these things are. |
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Post by Deleted on Jun 14, 2019 22:45:41 GMT
I experimented with a Stereo Coffee LDR passive pre a couple of years ago and it was a disaster. Money down the drain. Also, in my system, it sounded awful. Very sharp, glassy edged and bright. That’s not just my impression. Two of my mates were with me when we tried it and they are reliably hearing audiophiles. interesting, but the polar opposite from my experiences with one. guess it shows how system dependent these things are. What system is yours into, HJ? |
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Post by Deleted on Jun 15, 2019 15:21:13 GMT
hi, McIntosh amps and Sonus Faber Amati Homage, bigman. wanted to try an LDR, as I like the concept and Chris' SC slotted in very nicely with the MC312.
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Post by Deleted on Jun 15, 2019 17:19:23 GMT
hi, McIntosh amps and Sonus Faber Amati Homage, bigman. wanted to try an LDR, as I like the concept and Chris' SC slotted in very nicely with the MC312. Don't know why but I expected you to say Croft and Tannoys lol. Well I am pleased it's working for you in your system. That's what we all want, no matter how we get there. |
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Post by Deleted on Jun 15, 2019 17:19:46 GMT
Also good to hear some positivity about it.
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