Microphonic Cables

[ulysses]

hey all

just wondering of your experience with microphonic cables

i have a dimarzio woven cable with switchcraft jacks. about 10 foot. its about 15 years old.

it has gone microphonic which is disappointing as i paid about $60 for it new.

it makes the tap tap sound when you tap the jack.

before i bother wasting my time- i figured i'd ask your experience with them.

1. is it likely the jacks have any part to play in the tap tap sound? has anyone had switchcraft jacks go bad and make the tap tap sound? as switchcraft jacks are $6 a piece, i may reuse them on new cable

2. can the cable be cut up to make smaller patch leads that are not microphonic?

3. every time i finish playing guitar i coil the cable into  5x 2 foot loops and place it on top of the amp i was using. is this likely the cause?

4. how long do guitar leads usually last before they go microphonic?

cheers all

[blackieNYC]

Microphonic cables- yeah, it's a thing.  I use a lot of star quad expensive mic cable to make guitar cables, and sometimes this IS the problem.  And sometimes the cable is superior. 
Many describe this as a downside to low capacitance cable:http://www.thegearpage.net/board/showthread.php?t=1289102
But this might just be a couple dudes with opinions on the matter.  Thick jacketing, some "trilobite" pre-Cambrian animal is mentioned - I'm kidding, because the terminology and the science aren't worth much.  You've got a lot of cable.  Plug in, turn up, and flick the cable with your forefinger.  Least thumpy cable, put it into your guitar at the front end.  A thumpier cable may work fine getting stepped on, as a post pedal cable to your amp.  Some you'll want to throw out.  If they all suck, plug in a few at the music store and thump test them.  I don't think it has anything to do with jacks and plugs. 

[amptramp]

Cables tend to suffer from problems where the cable enters the jack.  This area get a lot of flex, so there is usually a spring wire or rubber extension going out of the jack at this point.  The cable itself may be microphonic because of:

1. Connections to the jack starting to go microphonic.  This is especially true of the shield.  Most jacks are good at terminating the central wire but not so good at terminating the shield.

2. Foam dielectric being flexed with a DC voltage across it.  This causes the capacitance to change and add to the current.  There is a current I = C * dV/dT from microphonic dielectric but also a current of I = V * dC/dT if there is a DC voltage on the cable and the capacitance changes.  Since the cable usually goes to a high impedance input, even a small current can result in a large voltage.

3. Breaks in the central conductor of the cable.  This usually happens near the connector due to flexing.  Copper tends to work harden so a cable that is nice and flexible in the annealed state (as manufactured) may become more stiff and brittle as time goes on.

The solution?  Fiber optic cables can't come soon enough.  No ground loops.  No susceptibility to interference.  Light weight.  Flexible for life.  All you need is the correct transmitter / receiver pair.

[samhay]

^The solution?  Fiber optic cables can't come soon enough.  No ground loops.  No susceptibility to interference.  Light weight.  Flexible for life. 
Perhaps so, but let's also add expensive and brittle to that mix.

To the OP - I would be fairly estatic if one of my guitar cables lasted 15 years.

[Mike Burgundy]

I've had Neutrik and Cordial do this (two heavy hitters, quality-wise) after long periods of time. The cable from my pedalboard to the amp is badly in need of replacement right now, and that's a Neutrik/Cordial one, I'm guessing about 15yrs old. It's run right next to the drumriser and has seen a lot of drummers' feet.
Cables wear, and that has an effect. I really believe the lifetime warranty on some brands (planet waves/ d'addario) is based more on the small percentage of people that are actually going to claim after 10 years, and less on lifetime durability. I just don't think it's possible with regular *normal* use -  (don't abuse it, but do expose it to heavy use and road carelessness - do you gently lay the coiled cable in a case and cover it at 2PM in the morning, or do you chuck it in? ).
Moisture might affect it too, I've once had a cable that had the shield oxidised completely all along its 20 foot length. That one was very microphonic. Honestly no idea where the moisture came from that caused *just* this cable to do that.
If the cable is okay along most of its length (tap it!), but reacts when tapped at the jacks, you either have a (partial) break in or near the plug, or a mechanical contact problem between jack and plug. The rest of the cable might be okay.

[anotherjim]

There's a common failure point in jacks too. The plug tip is basically a bolt or stud that goes all the way through with either a nut or riveting holding it all together and making contact with the wiring solder tag. If that comes loose at all you have a noisy plug. If it is loose, you can usually rotate the tip or sleeve with finger pressure. Riveted ones are usually scrap when that happens.

[ulysses]

thanks for the replies

i will try and see if the cable isn't microphonic in some spots and check the jacks separately

cheers

[ulysses]

hey all-

so i spent some time testing this cable- here are the results

1. only one end of the cable made the noise when tapped
2. the further i tapped the cable away from the jack the less volume the tap would make - lower than 1 foot from the jack taps are quite quiet but still present
3. i cut off the jack and 1 foot of cable (now a 9 foot cable)
4. tapping the cable with only 1 jack = silence
5. soldering back the jack onto the shortened cable = microphonic tap tap sound
6. desoldering the old jack and soldering on a completely different cheap brand jack from my spares box = silence
7. on close inspection the inside rivet on the jack looks looser than it once was. looks like the likely cause is letting the tip of the jack hit the ground which loosenens of the rivet holding the tip tight.

will order a new switchcraft jack and get back into business- and will stop letting the tip hit the ground in the future

i did email dimarzio who said they would replace the whole cable if i sent it to them in the usa. cost prohibitive from australia - but still decent service

cheers