[kin0kin]

has anybody measured what's the typical headphone cable (i.e. 650, k701...) capacitance @ 20khz?

 

[Garbz]

won't be more the a few pf. But it changes from cable to cable.

 

[kin0kin]

yeah just asking for an average possible number. but how much is a few pF?

the kimber ICs have an average of around 30-50pF (yeah i know it's and IC and they are braided). Safe to say a 3M long cable has about 20pF capacitance?

 

[DaKi][er]

I've never measured, but I was thinking it could be up around 100pF

 

[kin0kin]

Quote:

Originally Posted by DaKi][er I've never measured, but I was thinking it could be up around 100pF

not impossible.....I suppose kimber's 30+pF is "pretty good" to be able to retail them at their price.

 

[jcx]

google cable capacitance pF/ft

range is <10 - >50, eyeball average ~20 pF/ft so 20 pF total C is optimistic by an order of magnitude for 3 meters

high flex cable will have wires close together but use skinny wire, separation to diameter ratio controls parallel wire C (and dielectric const of insulation of course)

 

[Garbz]

well capacitance is by far not the only quality indicator. Infact some awesome cables have horrible capacitance measurments. What do you need the data for?

 

[kin0kin]

just to know what capacitance load will an amp be driving

 

[jcx]

http://www6.head-fi.org/forums/showp...&postcount=805

cable C is very important to amplifier stability at high frequencies

 

[kin0kin]

yes I'm well aware of that, it's the reason I created this thread.
I was not aware that the capacitance of the cables is almost around 500pF

 

[kilkil]

Is cable capacitance the reason why my amp will run happily with the 10' headphone cord plugged directly in, but when I plug in a 15' extension too it complains with loud buzzing? The loud buzzing only happens throughout about half of the volume range.

 

[Garbz]

quite possibly.

 

[tangent]

Quote:

Originally Posted by kin0kin I was not aware that the capacitance of the cables is almost around 500pF

Yes, I've seen this myself. It's one reason high-power op-amps are so popular for audio: they're often made to have high output currents precisely so they can drive heavy capacitive loads easily.

By the way, your "at 20 kHz" qualifier above isn't necessary. The capacitance is the capacitance. Changing the frequency you measure at only makes your measurement job harder, since it's easier to test capacitance at higher frequencies. You can talk about the impedance at a particular frequency, but that's a separate issue.

 

[kin0kin]

i wasn't quite sure why kimer kable stated their cable's capacitance at a particular freq, so i thought it was some sort of standard used in measuring them