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Post by svart on Mar 2, 2020 18:17:14 GMT -6
The ones and zeros are data and error correction works very well. The problem is that the clock is good ol' analog with all of its quirks. SPDIF optical transceivers are notorious clock jitter generators that can swamp a lot of common reclocking methods. Moving a plastic optical cable can actually move the image around especially with older ICs. Where optical can help is by eliminating ground loops. So you would be an advocate for ADAT (lightpipe) over SPIDF? Just trying to learn. Those are both data protocols. The physical optical cable is branded Toslink. Toslink can carry either ADAT or spdif.
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Post by Bob Olhsson on Mar 2, 2020 18:30:18 GMT -6
I'm an advocate for modern chips with an embedded clock and designs that aren't subject to ground loops.
We began our digital journey with incompetent interface IC designs. It got straightened out after the same engineers couldn't defend themselves with ABX tests when video directors pointed at their monitor screens demanding to know "what the f@ck is THAT?" I was at a SMPTE meeting where that actually happened!
The thing about digital is that when it doesn't behave as expected, something really IS wrong. People give manufacturers and developers a pass way too often.
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Post by EmRR on Mar 2, 2020 19:15:59 GMT -6
I should really replace my old ADAT-provided optical cables. Very rare that I use them, but when I need them it’s NOW. Any strong reasonably priced recommendations?
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ericn
Temp
Balance Engineer
Posts: 14,921
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Post by ericn on Mar 2, 2020 20:07:13 GMT -6
I should really replace my old ADAT-provided optical cables. Very rare that I use them, but when I need them it’s NOW. Any strong reasonably priced recommendations? Good luck Doug 😎 Seriously I think 99% of the Toslink cables out there are sourced from the OEM of the month. As an industry we just don’t use enough fiber to really matter, though most of us could probably benefit from more fiber in our diets.
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Post by svart on Mar 2, 2020 20:10:01 GMT -6
I should really replace my old ADAT-provided optical cables. Very rare that I use them, but when I need them it’s NOW. Any strong reasonably priced recommendations? The Amazon brand toslinks look pretty decent. Just don't get the cheap thin black plastic ones.
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Post by johneppstein on Mar 2, 2020 20:45:50 GMT -6
Interesting topic, makes me wonder. What’s easy for me to understand would be a glitch, a sudden extreme sample not anywhere close to the sample before or after. This would sound like a pop or click. So if there are random errors, you’d think it would it be obvious. What is tricky to understand, apparently when bits have errors, it can be close to the sample before or after. Ok here’s where it gets weird to me: if it was DSD then it’s easier for me to grasp, if the sample before/after was wrong, I’d assume overall the average of bits would sort of average close to the original signal and sound messy. With how we use packets to build a 24bit word, when a bit error happens is it somehow not bad enough to place the sample too far away from the original sample? I guess there must be some significant bits early on in the word that tell whether it’s positive or negative? So I guess an error has a a 1/24th chance of changing the positive/negative placement? And then maybe a 1/12th chance of placing it in the top or bottom half of any possible positive locations? I guess the more bits, the less the errors show up as audible click/pops, just more of an ugly nastiness? It's much more than that. The bits in the individual sample can be interrupted timewise or dropped altogether.
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Post by stratboy on Mar 2, 2020 20:47:47 GMT -6
I should really replace my old ADAT-provided optical cables. Very rare that I use them, but when I need them it’s NOW. Any strong reasonably priced recommendations? The Amazon brand toslinks look pretty decent. Just don't get the cheap thin black plastic ones. Oops.
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Post by svart on Mar 2, 2020 20:53:15 GMT -6
The Amazon brand toslinks look pretty decent. Just don't get the cheap thin black plastic ones. Oops. I mean, you can. I have a handful myself, but those are the kind I've had trouble with in the past. A few of them wouldn't hold tight in the sockets, one had the big bubble, etc. If you can get them for a dollar each, buy a handful because a few might not work Else, I'd get the Amazon basic ones.
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Post by tkaitkai on Nov 30, 2020 20:11:33 GMT -6
Reviving this thread because I just had a very similar experience.
Bought a $50 AudioQuest optical cable a few months back, mostly out of curiosity. Did some quick tests, didn't listen as critically as I should have, and pretty much just forgot about it.
Lately, my recordings have been sounding kind of lackluster — brittle/harsh and slightly distorted. Tried a whole bunch of stuff trying to tackle it. Mic placement, room treatment, mic cables, different sample rates, etc. I also finally got around to separating signal & power cables in the back of my rack (embarrassing, I know). Cable management seemed to help with the distortion, but the harshness was still there.
Swapped out the AudioQuest for a flimsy $8 Hosa and voila. Harshness gone. After reading this thread, I'm not surprised there was a difference — I guess I'm just surprised by how shitty the AudioQuest sounds.
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Post by svart on Nov 30, 2020 21:09:48 GMT -6
Reviving this thread because I just had a very similar experience. Bought a $50 AudioQuest optical cable a few months back, mostly out of curiosity. Did some quick tests, didn't listen as critically as I should have, and pretty much just forgot about it. Lately, my recordings have been sounding kind of lackluster — brittle/harsh and slightly distorted. Tried a whole bunch of stuff trying to tackle it. Mic placement, room treatment, mic cables, different sample rates, etc. I also finally got around to separating signal & power cables in the back of my rack (embarrassing, I know). Cable management seemed to help with the distortion, but the harshness was still there. Swapped out the AudioQuest for a flimsy $8 Hosa and voila. Harshness gone. After reading this thread, I'm not surprised there was a difference — I guess I'm just surprised by how shitty the AudioQuest sounds. To bookend your experience, it's not that one cable can sound different because of natural variation as is the case with analog cables, it's a case of the cable you replaced had a problem. The most common issues are that the ends don't hold tight. The end of the cable is supposed to smash up against the emitter or receiver device so that there's no gap and no diffraction. Another common occurrence is that folks bend the cables too tightly and fracture the plastic pipe inside which leaves reflective surfaces that can cause reflections that cause bit level errors.
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Post by tkaitkai on Nov 30, 2020 21:44:49 GMT -6
svart That's really interesting. The AudioQuest is basically brand new whereas I've had the Hosa for years. I wonder if the Hosa has one of the issues you described and I just happen to like that more. Either way, thank god I didn't spend more than $50 on that thing. Anyone want a cable?
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Post by svart on Dec 1, 2020 8:49:23 GMT -6
svart That's really interesting. The AudioQuest is basically brand new whereas I've had the Hosa for years. I wonder if the Hosa has one of the issues you described and I just happen to like that more. Either way, thank god I didn't spend more than $50 on that thing. Anyone want a cable? SPDIF and ADAT don't have error correction, so if they receive a small number of bit errors, they'll just pass them through and you'll get odd sounding audio up to the point where it's so bad that you'll start to hear crackling and popping as you get to the point of losing so many bits it creates locking issues. As I've mention before, I've had maybe two dozen optical cables over the years and the earlier TOSLINK optical cables were much better quality than those today. The last batch I bought to hook up a few ADAT converters, I bought a handful of the super cheap black TOSLINK cables. Of those, one wouldn't even seat in the optical port at all and one would intermittently work. The rest worked OK for what I was doing. I cut the skin back on the intermittent one and found it was cracked in multiple places. The one that wouldn't seat had a problem with the molding and it was loosely fitting once I trimmed it with a knife.
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Post by Omicron9 on Dec 1, 2020 9:16:10 GMT -6
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Post by svart on Dec 1, 2020 9:21:14 GMT -6
That's cool. I worked at a company that repaired and calibrated mobile fusing devices for single-mode fiber. It used to be a truck sized device but then shrunk down to a briefcase sized device, then down to something the size of a brick. Extremely precise devices that needed certifications, etc. But TOSLINK cables are usually just a plastic strand with none of the general qualities of communications-level fiber.
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