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Would this improve the quality of signal to a CNC machine?

(If it used USB for data transfer)

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Ian P26/02/2021 20:07:02
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2493 forum posts
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I've put this in the Tea Room as its mostly for discussing the pro's and conn's of cheap versus expensive cables between PC's and driven equipment.

Is seems that (apparently) transferring digital audio signals is best achieved by using only the highest quality cables. I have always understood that digital was digital and thought that as long as a USB cable transfers the 0's and 1's to the far end it would have no effect on the sound quality. Since the cables in the links below improve the sound quality, would these cable make CNC machined parts even more accurate?

devil

Edited By Ian P on 26/02/2021 20:08:11

HOWARDT26/02/2021 20:15:02
723 forum posts
25 photos

Cheap compared to some Kimber hi-fi cables. Not convinced that beyond switching away from bell wire or equivalent makes much difference, but then I only listen to LP,s.

Andrew Tinsley26/02/2021 20:15:46
1387 forum posts

Ah! That reminds me that gold plated pins on a 13 amp socket, definitely improve the audio from good analogue audio amplifiers!

Andrew.

Edited By Andrew Tinsley on 26/02/2021 20:16:09

Tom Sheppard26/02/2021 20:20:08
31 forum posts

Sheer twaddle. Electrons aren't fussy.

James Hall 326/02/2021 20:25:50
38 forum posts
8 photos

I think that someone has (apparently) been pulling your plonker.

IFF the bits are getting transmitted and received correctly the quality of the cable will make absolutely no difference.

Unless you are sending signals over too long a distance or in a high noise environment the chances are that a cheap cable should be fine (subject to correct manufacture).

Be wary of advice from hobby mags on these matters - particularly when talking about hi-fi - kit reviewers and bloggers have to maintain interest and hence sales; one of the ways they do this is by cooking up fashions for one expensive tweak or another. Remember when sounds weren't worth listening to unless your speakers were hooked up with cable capable of serving the National Grid - but with five million cores!

Emgee26/02/2021 20:27:25
2010 forum posts
253 photos

Screened cables usually provide better interference rejection.

Emgee

Andrew Johnston26/02/2021 21:21:20
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6009 forum posts
670 photos
Posted by Tom Sheppard on 26/02/2021 20:20:08:

Sheer twaddle. Electrons aren't fussy.

Hmmm, not an electronics engineer I presume? Electrons most definitely are fussy, and can be extremely annoying when they don't flow where you expect. smile o

The USB signal (1.x and 2.0) is differential, transmitted over a twisted pair with a nominal impedance of 90 ohms. If the impedance is wrong and/or the lines are not terminated properly then reflections and overshoots will occur, ultimately leading to loss of signal integrity.

A digital signal is really an analogue signal. In some ways digital is more challenging than analogue as the fast edges imply a larger bandwidth than might be suggested by the data rate. If the transmission channel is not linear, ie, non-dispersive, then distortion of the signal will result leading to problems in decoding the signal. There's a vast literature available on the transmission and decoding of digital signals, with some pretty hairy mathematics.

Having said the above a quality USB cable will not be expensive. The cables linked to in the OP are nothing to do with technical ability; they're intended to separate fools and their money.

Andrew

Ian Parkin26/02/2021 21:52:28
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931 forum posts
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I see that in Ians links to the cables they can add on a cable of  three thousand pounds a contract enhancer for only an extra £3.20

must be some special snake oil...

I’d love to know how many cables they can sell at those prices

Edited By Ian Parkin on 26/02/2021 21:53:18

James Hall 326/02/2021 21:52:37
38 forum posts
8 photos

A digital signal is most definitely NOT an analogue signal. Over copper it is transmitted by way of an underlying analogue signal, but that is a different matter and the two signals are quite discreet.

Ian Parkin26/02/2021 21:56:58
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931 forum posts
221 photos

And look at the cost of mains cables a 10m iec set for only £13,800

where do they think the electricity comes from to supply the mains socket

 

makes a new myford look good value

Edited By Ian Parkin on 26/02/2021 21:57:49

SillyOldDuffer26/02/2021 21:58:19
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7131 forum posts
1571 photos

USB doesn't provide any error correction itself so maybe a bad connection due to an unshielded cable in an electrically noisy environment or wobbly plugs could corrupt the digital stream.

I don't know what hi fi systems do, but computers send and receive data in check-summed blocks and usually ask for repeats until they get clean data. Broadcast digital tv and radio can't ask for a repeat so they just drop the offending block causing audio to go silent or the screen to pixelate. The quality of received segments is perfect, but they are interspersed by obvious glitches. Unlike an analogue system It either works or it doesn't: there is no general low-level loss of quality, just good and bad blocks.

Maybe hifi systems use usb cables as ordinary audio connectors and aren't digital at all. A convenient bodge, but prone to analogue defects, that might be reduced by a decent cable.

What's needed is a good dose of double-blind testing. For some strange reason it's never done...

Dave

Andrew Johnston26/02/2021 22:10:42
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6009 forum posts
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Posted by James Hall 3 on 26/02/2021 21:52:37:

..........and the two signals are quite discreet.

That's a new one on me. I've never seen a signal, analogue or digital, that aimed to avoid social embarrassment. smile

It's convenient, and may be logical, to think of a digital signal as being one of a small set of values. But in reality, however it exists, the actual signal is analogue. Would a FSK signal be analogue or digital?

Andrew

Martin Kyte26/02/2021 22:48:23
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2346 forum posts
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I have to agree with Andrew in this one. The signal is analog. The signal is interpreted as digital by the receiver circuit defined by it's threshold levels. Digital coding, analog transmission. You could transmit digitally by sending single electrons with the data coded in spin up or spin down but the cost of your system would make the USB cables above seem cheap.

regards Martin

Martin Connelly27/02/2021 08:16:12
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1705 forum posts
181 photos

My ears are well past their best before date. I doubt any amount of money thrown at a sound system will ever make it sound as good as when my ears were still in the first flush of youth.

Martin C

Hopper27/02/2021 08:38:35
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5427 forum posts
134 photos

Yes, I just spent $1,000 on a new sound system. Then realised the sound is only going to be as good as my two hearing aids!

Oh well, at least it's loud enough that I can't hear my neighbour banging on my door, or his bloody dog barking.

Ady127/02/2021 08:56:55
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4345 forum posts
675 photos

Plus our hearing degrades quickly as we age, particularly for the higher ranges

Those fabulous ABBA sounds of our youth can never be as good in our old age no matter what we do

Chap on my dog walk showed me with a phone app, neither of us could hear a thing in the higher ranges, even though those sounds were within the audible range for a human

Hopper27/02/2021 09:28:58
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5427 forum posts
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Yep that's me. Can't hear the beeper on the microwave any more or the "lights on" alarm beeper when getting out of the car. Shoulda worn earplugs in all those power stations I guess. Let alone Harleys with straight pipes and Nortons with megaphone mufflers. But that would have been uncool.

Dave Halford27/02/2021 09:56:43
1439 forum posts
12 photos

You certainly get errors at 2mbit and above from a bad connection so decent connectors are worth paying for and it also helps that the impedance of the cable is what it says it is. Good screening will help stop the VFD noise getting on the cable.

Will it make a difference CNC, no ideasmiley

James Hall 327/02/2021 10:13:25
38 forum posts
8 photos

Martin Kyte: you may well agree with Andrew Johnston on this one but you would, with respect, both still bee wrong.

This really is DigComms 101 - kids' stuff. To say that a digital signal is really an analogue one because it is carried over an analogue channel is as ridiculous as saying that an analogue signal is really a piece of wire because the piece of wire carries the electrons. I've tried to think up an illustrative analogy with the difference between the meaning of word and a dumb spell-checker for you further amusement - but it proved to be too contrived.

Anthony Kendall27/02/2021 10:33:04
103 forum posts

Being a simple person, I like to look at it like this.

Digital signals are decodeable providing noise added does not approach the amplitude of the digital signal such that it is not possible to reliably distinguish between a nought and a one.

The length of the cable will have an affect - as distance increases, the amplitude of the wanted signal decreases and the noise gets proportionally greater, depending on the environment.

Thus, any cable should be low loss and screened.

To answer the OP - unless you are going to send signals to your mate's house down the road, the normally available screened cables will suffice. This should cost no more than 2 quid per metre. It might even get you to your mate's house as well!

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