How can you tell good cables from bad ones with a multimeter.

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chrisghost

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Can I use my multimeter to tell a good quality cable from a bad quality cable?

I got to know a guy a while back who has a studio, but he can't solder. He was used to throwing defect cables into a big cardboard box under his desk and he's now donated that box to me.

The cables are an array of different brands and qualities. I want to repair and re-use what's worth re-using.

Thanks.
 
you can use a multimeter to check for continuity, but that wont tell you if its "high quality" or poor quality- it'll just tell you if the cable is passing signal. In my limited experience I've NEVER seen a *cable* fails. Its always the connector or the solder joints to the connector.
 
Ohms scale. You should see virtually no difference going end to end on each leg and/or shield than putting the meter leads together –solid good circuit, 'zero ohms. Given solid path end to end, there should be the same reading from leg to leg or leg to shield as the meter leads not touching anything –open circuit, 'infinity ohms.
Gotchas-
Meters have different levels of range (sensitivity' if you will). Hold both lead tips -leads not touching together, firmly in one hand. If you see a lower reading than open' leads this meter is reading the rather high resistance of your skin. Don't confuse that with your 'open test. You may have to figure out how to isolate yourself from the cable.
Connections, shorts between legs, and in particular with old stomped on cables, the shield braiding can be breaking down.
This means you will want to measure while moving the cable around to see faults. (Not so easy on the male end of an XLR for example)
It may in fact be easier in some cases to just hook the thing up with a constant signal, jiggle, twist and listen. Try it at higher gain to listen for crappy shield.
Like Jeff mentioned 9 times out of 10 it'll be at the connector or the first several inches where the cable see the sharpist bends. With crappy, second-hand soldered joints and wire, a lot of times it's just hack it there and start fresh.
 
Sure, everyone should have a multimeter. The red Sears Craftsman ones with audible continuity that go on sale for $15 or so are great.

But the multimeter won't tell you if it works great, only if it works or not. Your ear will tell you if the cable is acceptable better than anything else.

The best way is to get an amp and a sound source (guitar, synth, tape deck etc) and start with a known-to-be-good cable and then start substituting the questionable ones.

You might want to get some Caig Deoxit as that's pretty much the industry standard electronic cleaner/lubricant.
 
You'll also find it helpful to have a second set of multimeter leads with alligator clip ends rather than probes. Holding probes against the connector while shaking the cable all about is really difficult.
 
continuity is about all you'll learn from it... good to have a meter around though... as to the cables i bet if ya simply cut off the ends by about an inch or two and resolder the connector back on you'll be up and running...
 
Thanks a bunch for the info Mixsit. Your theory makes a lot of sense. Can anyone back up Mixsit's theory, just in case?

Thanks Commanda, alligator clips should be pretty practicle.
 
chrisghost said:
Thanks a bunch for the info Mixsit. Your theory makes a lot of sense. Can anyone back up Mixsit's theory, just in case?

Thanks Commanda, alligator clips should be pretty practicle.
Click to expand...

Mixsit it spot on to me.

Multimeters aren't as good as just trying the cable with a source and an amp.

Plug the thing in, sing in the mic or play that guitar and wiggle the cable near the ends - try to make it fail.
 
Just to be clear: I'm not talking about breaks or bad connections, I can handle that stuff, no problem.

I'm talking about the SOUND QUALITY of the cable. Cheap cables don't let the sound through very good. (Which sounded weird to me too, when I first heard it.

Saying that, if the sound doesn't go through very good, that's probebly because it has resistance, which you measure in Ohms, so Miksit sounds spot on.
 
chrisghost said:
Just to be clear: I'm not talking about breaks or bad connections, I can handle that stuff, no problem.

I'm talking about the SOUND QUALITY of the cable. Cheap cables don't let the sound through very good. (Which sounded weird to me too, when I first heard it.

Saying that, if the sound doesn't go through very good, that's probebly because it has resistance, which you measure in Ohms, so Miksit sounds spot on.
Click to expand...

Slightly different subject there then. If the cable is decent, bobust build, has a quality shield and/or lagre enough wire for the job to begin with (for speaker cable size and length matters), other than issues with them getting noisy from movement (shield breaking down I presume?) and out and out breaks and intermitents.. but that was "...but he can't solder. He was used to throwing defect cables into a big cardboard box .."
Now you want to measure the dif between say a 25' $10 vs $30 or whatever? Hmm. Nope. I wouldn't know how you'd do that with a multi meter.
 
oh.. and any that have molded plugs probably arent worth screwing with... they almost always use shitty cable as well as shitty connectors... ymmv...
 
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