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Posted by birdculture 3 days ago

A nearly perfect USB cable tester(blog.literarily-starved.com)
233 points | 117 commentspage 2
atoav 12 hours ago|
One thing to realize is that especially for high resolution video cables these cheap testers can't really deliver. The way to test them is a eye diagram (see: https://incompliancemag.com/eye-diagram-part2/ ) and testers with that capsbility cost upwards of 10.000 Eurodollars.
jmalicki 11 hours ago||
So you're saying there is something to audiophile grade HDMI cables?
scq 11 hours ago|||
No. What it can affect though is the bandwidth of the cable, meaning e.g. for HDMI cables, they might not support higher resolutions or framerates. If it's on the border you might see random disconnects or screen blanks.

The quality degrading is not something you will see, as it's a digital protocol.

"Audiophile grade" HDMI cables are likely to just be a Shenzhen bargain-bin special with some fancy looking sheathing and connectors. I would trust them less than an Amazon Basics cable.

fmajid 11 hours ago||
Indeed. If I want super high quality cables, I get them from Blue Jeans Cables, who tell you exactly what Belsen or Can are cable stock and what connectors, as well as the assembly methodology.
fmajid 1 hour ago||
Belden or Canare. Pesky autocorrect.
HPsquared 11 hours ago||||
With digital signals and ECC, the cable need only be "good enough" to get perfect data transfer through the system.
atoav 9 hours ago|||
Correct. But especially if you're using long cables a cable with more "headroom" in the eye diagram will perform more reliable than one that is just at the edge of breakup.

For home use that doesn't matter usually, but I for example run events where I need the cable to work also after 10 people stepped on it and then this can become a significant thing.

Not in terms of quality, but reliability.

jmalicki 10 hours ago|||
His link made very clear the issues of jitter and flickering.
tom_alexander 9 hours ago||
These two statements aren't mutually exclusive. The link is looking at the analog signal through an oscilloscope. The person you replied to is pointing out that after decoding and applying error correction, you can still end up with the same digital signal output. So the eye diagram charts are useful for detecting the quality of the cable, but as long as the quality is past a certain threshold, it does not matter.
atoav 11 hours ago|||
No. What I am saying is that it is hard to test the quality of a 8K 240Hz 4444 video cable without having a device that can send and receive this or even higher.

If you send bits across a line fast enough you're grtting into the territory of RF electronics, with wrong connector or conductor geometry you will get echos on the line and all kind of signal loss. A good digital protocol should keep this at bay with error correction and similar mechanisms, but if you want to know what the good cable is on a better than binary scale of works/does not, you need to look at these things.

jmalicki 10 hours ago||
I just need to make a cable with better eye diagrams so I can market it to AV enthusiasts with "golden eyes"!
TeMPOraL 10 hours ago|||
Our cables are so good that their eye diagrams look like a photograph of a cross-section a gold analog AV connector. That is not a coincidence!
atoav 9 hours ago|||
Well the thing is better doesn't mean better quality here. Better means you can use a longer cable or abuse the cable for longer till it dies.

This is a big part of what makes any pro gear expensive: reliability. If you just connect your home hifi to your speakers in an acoustically untreated space, you could also just use a bunch of steel wire coathangers and get an indistinguishable result. Even a el-cheapo store brand music shop cable will do the trick for years if you don't habitually change your setup four times a week (most people don't).

But if you need reliability and predictability in a studio or live context giving a damn about cable quality is mandatory since a broken cable in the wrong place can ruin your day and reputation. But it is an absolute myth that they will affect the sound in any meaningful way.

Exeption: guitar cables. The capacitance of guitar cables can shift the resonance frequency of the pickup up or down leading to audibly different results. But that id no magic either, you could just take a low capacitance cable and add in arbitrary capacitor for 10 cents as needed.

jmalicki 9 hours ago||
I have seen shielding and gauge make quite a difference for cables carrying analog signals!
mmastrac 7 hours ago||
Can you rewrite the emarker chips?
Liftyee 7 hours ago||
Brilliant little device. I will be picking one up ASAP!. Didn't know that lying cables were a thing but I have a ton of charge only cables?!

I speculate USB B wasn't included because there are only really two types, 2.0 (regular size) and 3.0 (has an obvious extension on the connector). There also don't tend to be power-only A-B cables because they are usually found on printers, Arduino s, ... And not for charging devices.

Fun fact: A Xiaomi fast charge cable (with orange plugs) has an extra contact on the A end to support USB C PD out of a USB A charger.

kotaKat 7 hours ago||
Similarly: Is there a USB-C power delivery adapter to force directionality? I needed to siphon off power from small batteries into a larger pack (that could supply more power out than the small packs) in a power outage. I absolutely could not force my larger power station to accept a charge and it kept pushing power back the wrong direction despite which ends of the cable I plugged in first.
ssl-3 4 hours ago|
It's ugly, but yes: https://www.anker.com/products/a8895?variant=45839927509142

That cable has one power input (that is only an input), and two outputs (that are only outputs), and a brainbox in the middle to direct the circus.

If we label the connectors as A, B, and C, then it works like this: A charges B and/or C, and other charging directions are no-op.

The less-complex way is to use a USB A to C cable, if that's appropriate. With these, the A side is always the source and the C side is always the sink.

---

And yeah, it's annoying. I got a cheap lithium car jump starter several years ago with some neat power bank features (like 60W USB PD in/out, on one port). So I plugged it into my phone with USB C at my desk, and discovered that they'd charge eachother seemingly randomly. While changing nothing, I'd look over and sometimes the jump starter would charge the phone, and sometimes the phone would be charging the jump starter. The conglomeration formed a heater, with more steps.

(Back and forth with the same poop, forever.)

kotaKat 3 hours ago||
Ah, yeah, I remember those. That miiiiight work for my use case...

--- (I remember. The poop.)

Onavo 13 hours ago||
I just want one that tells me the maximum voltage and current supported by a USB C cable.
fmajid 11 hours ago||
The Treedix will tell you that, as it is a feature of the eMarker chip (no chip means 60W).
contingencies 11 hours ago|||
Got this recently for USD$3 on sale: https://www.aliexpress.com/item/1005006848187940.html
wolfi1 12 hours ago||
there are several: one that is moderately priced and which I consider myself to buy is the JOY-IT UM120
Onavo 11 hours ago||
Thanks, why do you prefer that particular model?
wolfi1 11 hours ago||
I wanted to have a model which tells me the modes which are supported and which is actually selected for a reasonable price and which I can order at a reasonable trader. this model seems to do the trick
Modified3019 12 hours ago||
I’ve had one for a while as well. I don’t use it often, but frankly I couldn’t sort my cables without it.
Eisenstein 11 hours ago||
Hopefully they used connectors with a high mating cycle rating.
pugchat 3 hours ago|
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