Phone lines do carry DC, They also carry Audio and if I remember correctly the characteristic impeadance of a phone line is 600 ohms. In the case of phone lines the characteristic impeadance does come into play because of the long runs of cable.
shaun
Oops! I just remembered some of my college training and characteristic Impeadance does apply to DC aswell.
Shaun
"Shaun"
** Yup.** Nope.
** The mud sticks.
.... Phil
"Shaun"
** Further to you question:An electrically "short" transmission line ( with low losses) looks like a series inductor if the load end is shorted and looks like a pure capacitor if it is open.
Only time it does neither is if you load it with its characteristic impedance.
One trap with the low Zo speaker cables that I mentioned before is they necessarily exhibit high capacitance per metre - ie 5,000 to 20,000 pF. At some very high frequency ( ie MHz) the impedance of nearly any speaker is in the hundreds or thousands of ohms - so the cable acts like it is open at the load end and presents a high capacitance ( with high Q ) to the drive amplifier. Some hi-fi amps can burst into RF oscillation with such a capacitance.
The simplest fix is to add a " zobel" network at the load end of the able - a 0.1uF poly cap and 8 ohm, 1W resistor in series does the job.
.... Phil
A problem with poorly improvised speaker wiring is impedance and capacitance together. Single conductor wires strewn about for long distances don't work well.
-- I will not see posts or email from Google because I must filter them as spam
"Kevin McMurtrie"
** There are two simple and cheap ways to make a very good speaker cable.In both cases, series inductance is low and parallel capacitance small.
..... Phil
"The Golden Reference speaker cable uses Cardas' patented "Golden Section" design, which in this case employs "multi-gauge stranding in a symmetrical, 12 conductor, helical triad of quad-axial planetary arrays of golden ratio, constant Q conductors". Whew! If, like me, you're not sure what that quote really means, look at the accompanying diagrams to see how the cable is put together. The smallest wire strands are at the center of the conductor bundles, and wrapped with copper Litz wire. The cable is constructed in a very complex manner with thin walled air tubes that provide a dielectric; internal Teflon jackets that surround the bundles of conductors; a Teflon graphite composite shield; several layers of Teflon binding and spiral shielding; capacitively coupled soft-shield drain conductors; and a final outer urethane jacket. It's obvious from their construction that a huge amount of thought and expense go into making the Golden Reference line of cables."
These are known for extracting the maximum amount of money per foot from "expert" audiofools. That "Golden Section" is indeed golden! .....VWW
"VWWall"
** Thanks for your input - Mr Vee Dub.The multi-stranded cable I alluded to was known as " Mogami Cable" as well as a few other trading names. Enamelled wire, 72 strands per conductor, clear PVC centre support and outer sheaths - only 7mm in dia.
Nothing bullshit about it really and sold for $3 a metre, off the reel, in the late 1970s.
Terminating the ends was fun - one had to separate the green and copper coloured strands and twist the bundle tightly - then use a very HOT soldering iron the burn off the enamel insulation.
I liked to fit 4mm "banana" plugs to finish the job.
.... Phil
There are 600 ohm speakers, as well. You stated no one would ever run a speaker line 3.75 kilometres, when some are longer than that.
-- You can't fix stupid. You can't even put a band-aid on it, because it's Teflon coated.
get
en
dond
dpensive
eries
tes
ore
se
Thanks Phil, I was summing X-pF/foot by 200 feet, and wondering how
10-40(?) nF is going to matter.George H.
g.
ts (=3D
"George Herold"
Thanks Phil, I was summing X-pF/foot by 200 feet, and wondering how
10-40(?) nF is going to matter.** See my post here, a few hours ago.
.... Phil
o r
. =A0At
in
the
ob.
"scribbling furiously...." L =3D 6.4 uH? (Just guessing at Zobel network.)
George H.
"George Herold"
"scribbling furiously...." L = 6.4 uH? (Just guessing at Zobel network.)
** Huh ??The idea of the 8 ohm "zobel" is to load the fancy cable with its characteristic impedance and so render it resistive and benign at HF.
No transmission line effects exist in domestic audio ??
Wot absolute bunkum.
... Phil
Yeah I've been reading along. The flat ribbon cable are 1000's of pF per foot. I'm reminded of the story I heard about the first trans- atlantic telegraph cable. They closed the switch at one end and the mirror galvenometer on the other side slooowly responded.
George H.
"Impedance and capacitance together"? What the hell does that mean? The best speaker cable is zip cord (14GA, if you can find it).
a
tor
At
is
tI thought I was calculating the inductance of the speaker. (Sorry I'll have to google zobel network.)
George H.
Want to explain that one? You should seek a tuition refund.
a
tor
At
is
tYah, do you mean this circuit?
George H.
"George Herold"
Yah, do you mean this circuit?
In my example, the " anomaly " is the fact that nearly all hi-fi speaker
*systems* have a steadily rising impedance above 20 kHz or so. The appropriate time constant ( R x C ) in this case depends mostly on sort of the frequency one might expect a hi-fi amplifier to oscillate at when loaded with a pure C within range of values involved.BTW:
" The simple things you see, are all complicated ... "
.... Phil
"Phil Allison" wrote in news:8qgnnlFbboU1 @mid.individual.net:
Bullshit. They'd never have been able to withstand the whining horizontal output transformer or yoke in an old analog TV all those years if they could hear that high. Your teenager would have been listening to the 19 Khz pilot tone of ever FM radio station, poorly filtered by the cheap receivers, too.
I'm paying the price for all my audio sins at 65. I've been listening to about 12 high pitched imaginary tones for 30 years after listening to axial marine ducted fans in the Navy so long. I can't shut them off...The lowest tone I'm "hearing" as I type this at 3:30AM because it keeps me awake late is around 11Khz.
I could hear a faint whistle from the horizontal output of the old TVs when I was young, but it was quite rolled off....just like the RIAA Equalization on all the records/tapes and FM radio.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.