Coaxial vs CAT 5

Quite so But I don't think that was what I was implying. I simply tried to express the idea in a few sentences. I tried to find a graph, that showed the effect.

Many years ago, I studied those graphs in my work.

SOP is every 6Kft, with the first coil being 3Kft from the CO.

That spec was adopted for {real} T1. There, the reason for the initial 3 Kft was the CO was a really noisy place with all those crossbar and step switches clacking away; so they wanted more noise margin on that leg.

I've never grokked what good the 3Kft spec was with analog...

Or maybe, they wanted the loading coil in the middle of each 6K segment.

Hmm, a different way of thinking about it. You could well be correct.

In case it was not obvious; having T1 design meet the 3Kft/6Kft rule means a crew can go to that point on the cable, and mount the repeater on the same pole as the existing "can" with the coils.

Fewer cable openings, less work, lower cost. For all its faults, Ma's engineering design was well thought out toward minimizing low TCO/lifecycle costs; the opposite of our current obsession with ""lowest price""....

Yeah, true. Howwever, Ma Bell thought that telephone networks would always be circuit switched, and never considered alternative technologies such as cell phones, IP and DSL for the last mile.

Now SBC is going to buy AT&T, 'Ma Bell' being taken over by one of its baby spinoffs. MCI, too.

Thanks for all that info Ro

(someone wrote)

(snip)

Professional equipment uses balanced low impedance for audio signals to avoid that problem. Transformers on each end. I believe it is usually shielded twisted pair, but UTP might work.

Again transformers should work, but this time the low impedance side for the speaker/amp and high for the UTP.

The usual standard uses a transformer called 70.7 volt on one side, and 4/8/16 ohm speaker terminals on the other. Of course the actual voltage depends on the signal going in.

Those should work, though I have never tried it. They are commonly used for PA systems in schools and such. Otherwise, home intercoms usually use higher impedance, maybe 40 ohm, speakers.

-- glen

If you drive it with a 100 ohm source, then yes, but most line outputs are 1000 ohms or so. 15pF/ft and 300ft is 4500pf.

4500pF*1000ohms is 4.5us, f=1/(2pi*4.5us)=100kHz, will have some rolloff at 20kHz.

Telephone wiring uses 600 ohm source impedance and longer wires. The parallel capacitance is balanced by series inductors spaced out along the cable.

-- glen

Actually, telephone cable has appreciable rolloff within the voice frequencies, which is why loading coils are used when going significant distances. The coils flatten the attenuation within the desired bandwidth, at the expense of higher frequencies. However I doubt that roll off would be significant at the distances used in a home.

As for those "Golden Ears" types, don't you know that their ears are so good, that they can hear things that are physically impossible to hear? A few years ago, there was a columnist (Larry Klien IIRC) in Radio Electronics magazine, who'd occasionally take aim at those Golden Ear types. Seems some of them can listen to two different audio systems, in different environments at different times and tell which one sounds best, but they also reject A-B tests as invalid. They're also the idiots who tend to buy stuff such as Monster cables and other such junk.

Jeeesh, this thread came back from the dead. When people ask about using telco wire for HiFi speakers (amps into a low impedance) is making a mistake and it's possible to show rolloff, IMO. (I use 12 ga stranded power tool extension cord wire cut to length. It comes in pretty colors and handles nicely and is cheap.)

As for "golden ears", I find that if I'm equipment shopping, when I carry a couple records (it's been *that long*), I can go system to system or store to store and hear different things, but for me it's a skill that needs to be practiced. Once I've bought some kit I just enjoy it and cease to listen diagnostically. I've never done AB tests.

I have blood relatives that have perfect pitch and can identify specific musical instruments on classical recordings.

I dropped my Golden Ear magazine subscriptions years ago. I once told the editor for one of them that I thought that spending the money on

*msic* was mutch more satisfying. He wasn't happy.

Agreed. The speaker cables are vastly overpriced. OTOH I find the price for a Monster "patch cord" pair, well made, with heavy gold plated RCA plugs (4 of them) for $20 or so not unreasonable. It's been years since I needed to buy any.

I use their gold plated spade lugs and bannana plugs for the same reason.

One thing pointed out by Larry Klien, was that for most purposes, ordinary lamp cord was fine for connecting speakers. Anything else is a waste of money. However I'd suspect using telephone cable or CAT 5 might have resistance loss issues, when handling low impedance loads, over significant distances.

When defining "junk" I guess it's best to consider cost/value. The higher the ratio, the more likely it's junk. ;-)

Bottom line, are you getting value for money?

That gold plating is another issue. If gold is so good (yes, I know it doesn't tarnish) why are low noise instrumentation connectors made with silver plating? Does the gold actually improve anything, other than vendors profit?

Well, for them hearing has passed from a sensory experience into a psychological experience. Perhaps a religious experience. In a free country, we really should respect other religions, even if we don't much believe them.

Monster cables are not junk. They're usually fairly decent midrange cables but sold at outrageous prices with the most appalling pseudoscience flim-flam.

-- Robert

One of my pet peeves has been the quality of connections on the speaker circuit. People spend $x,000 bucks on a 200w amp and speakers and they find that they have cheapo 5-way bannana jacks that *can't* be torqued enough to break the oxide layer IMO, and gold doesn't have that problem.

I once measured the voltage drop across all 8 commections in a stereo setup with a millivolt DMV and found it was *very* hard to get a low resistance connection. Add 4 crappy connections in series with too much 18ga wire connected to a 4ohm speaker and you're not getting your money's worth. I think the worst connection I saw was .5 ohm and with dynamic music i guess you've got spikes in the amps range. I was measuring voltage drop with a .5 amp 400 Hz tone. (*loud*)

The gold spade lugs are nice but the area pressure on a bannana jack is not enough to bake a really goot connection, IMO. At least on the equipment I've had.

/end of rant/

Silver is the best conductor and makes good contact in connectors.

When I asked that question, I was referring to audio cables etc., as per the discussion. Computer chips have their own issues, low noise isn't one of them.

Well, you could at one time spend a few thousand dollars on a Yugo... ;-)

One thing I often see, are people with spoilers etc., on the back end of a Honda or Nissan. I wonder how much "value" they bring. ;-)

I don't think "junk" has any element of cost/value. It seem to more equate to "garbage" -- low absolute value.

High-end sports cars definitely are not "junk", but often have high cost per unit value.

-- Robert

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