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Turntable question (cables)
fewtch
post Jun 10 2002, 19:33
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OK, so most MM turntables cartridges put out 2.5-5mV, and this miniscule voltage is run through maybe 6 feet of (often) poorly shielded RCA cables to a phono preamp.

Would it be worthwhile to purchase a set of "monster cables" or other well-shielded special audio cable terminating in RCA plugs, and solder those in to replace the defaults coming out of the turntable? Anyone ever do this and notice an improvement (seems like there could be a big one)? And how about a thicker ground wire, possibilities there too?

Cheers...


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Jan S.
post Jun 10 2002, 19:35
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If you ask the ppl that sell these they will tell you there is a difference.
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Pio2001
post Jun 10 2002, 20:54
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When I was experimenting on this, I found differences for CD Playback, but not for Vinyl playback. I think the sound of vinyl was not accurate enough to be affected by the cable quality.

I don't think the gauge of the ground cable will make any difference. Its position and the place where it's plugged would be more important IMO.
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fewtch
post Jun 10 2002, 21:14
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QUOTE
Originally posted by Pio2001
When I was experimenting on this, I found differences for CD Playback, but not for Vinyl playback. I think the sound of vinyl was not accurate enough to be affected by the cable quality.

What about reducing interference picked up by the cables and transmitted to the phono preamp? Those things greatly amplify any input signal, so if the cables coming from the turntable are picking up a radio station or something... :ponder:

It's hard to believe that at (say) 2.5mV from a cartridge, 6 feet of unshielded (or under-shielded) plain old steel wire isn't adding significant impedance and picking up RF energy.


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Pio2001
post Jun 10 2002, 21:59
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Are you saying your cable is not shielded ??? In that case, change it at once tongue.gif

The only problems I got with interferences were with the Planar3 (no ground connector) and the Denon DL-110 catridge (special "high" output moving coil).
No problems with the Stanton Trackmaster on the Technics SL-3100, with which I tried different cables.
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fewtch
post Jun 10 2002, 23:12
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QUOTE
Originally posted by Pio2001
Are you saying your cable is not shielded ??? In that case, change it at once tongue.gif 

Not very well shielded, compared to "monster cable" and such. Not only that, but those expensive cables are "directional" (probably something to do with molecular alignments in the wiring).... it still seems that such low voltages (especially) would benefit from stuff like this, but if you say you tried it...

But did you ABX the differences? (LOL)... tongue.gif

Maybe I'll try it anyway, it certainly couldn't hurt anything.


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Case
post Jun 10 2002, 23:16
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QUOTE
Originally posted by fewtch
Not only that, but those expensive cables are "directional" (probably something to do with molecular alignments in the wiring)

You do know that this is BS. The direction of the cable has no effect on the signal going through.
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fewtch
post Jun 10 2002, 23:33
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QUOTE
Originally posted by Case

You do know that this is BS. The direction of the cable has no effect on the signal going through.

Why not? It depends on the material the cable is made of. A diode certainly has an effect depending on direction of current, I don't think there's a reason why a cable couldn't be made which conducts better one direction than another (why you'd want to is another story).


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daniel
post Jun 10 2002, 23:55
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I found on the net some "scientific evidnce":eek: :eek: about cable directionality. I guess it was the cable company:D . But seriously, fewtch, don't use those cables that came with your cd player/TT/amp/cassete deck etc. etc. The cheapest desent cables will do. I measured those cheap ones. Each one had 0.5 to 1ohm impedance! Really. I'm not kidding. Even my 5m speaker wire has 0.0ohms!
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fewtch
post Jun 11 2002, 00:02
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That's what I'm afraid of, that certain cables will have "too much" impedance for a ~2.7mV phono signal... who knows what they used for some of those vintage turntables. You don't want to impede a tiny voltage coming from a phono cartridge, and especially you don't want to add RF noise.


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daniel
post Jun 11 2002, 00:05
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Despite an increasing tendency for manufacturers to mark cables directionally, no evidence was found
under controlled conditions to support the notion that speaker cables are directional. It was found, on
the other hand, that merely laying a cable diffe rently could affect the inductance and capacitance.
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Case
post Jun 11 2002, 00:08
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QUOTE
Originally posted by fewtch
Why not?  It depends on the material the cable is made of.

It's been long time since I read physics, so I can't prove it with fancy theories. Maybe if I had some old school physics books around I could find some information.
But to me this is similar to green pen, pure marketing trick. But this would be easy enough to prove by someone who has such cables, all it takes is to measure resistance of the cable in both directions and show the results.
Btw, I tried searching some information with google and all I found was this. I find it amusing.
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daniel
post Jun 11 2002, 00:20
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QUOTE
all I found was this. I find it amusing

Damn, this could be called scientific compared to audioquest claims.
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daniel
post Jun 11 2002, 00:25
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When biwiring, the two cables used must either be identical, or have essentially identical designs. If the cables have different inductance or capacitance, they will cause different amounts of phase shift.


So what! If you know what you are doing then this claim is relevant only for transcient perfect loudspeakers. And I havent seen those in sale. Only diy-ers do those things (maybe some very exotic speaker manuf-er)
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Pio2001
post Jun 11 2002, 00:28
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Of course, the mere resistance of the cable won't prove anything. It would be the same as judging the quality of an ampli relying only on its power.
The only thing to do is recording the output while in use. Unfortunately, the differences are cahotic from a recording to another, even if you record twice the same CD right from the analog output : no way to cancel the recording inverting one to paste on the other.

The only directional cables I saw explained were "twinax" cables. Two cores, one for the signal, one for the ground. The shield is connected to the ground at one end of the cable only. The shield not being conducting (disconnected at one end), it prevents current to be inducted in it by ground looping.
When you connect two devices that are both grounded via their power supply (creating a loop), you often get some Hum. This kind of cable is very effective at cancelling this hum (breaking the loop, or more exactly, shielding a part of the loop).
It is said that it's better to plug the connected end at the source. Again, I didn't check if it was true.

XLR cables have a core used for the ground signal, but I don't know if their shield is cut at one end.
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Pio2001
post Jun 11 2002, 00:46
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QUOTE
Originally posted by daniel
 
Damn, this could be called scientific compared to audioquest claims.


Wow ! At last we know WHY silver is used in cables biggrin.gif

In radio-frequencies applications (way above the audio range) skin efect can be a serious problem, overcome by silver plating to reduce resistance at the surface, where the bulk of high frequency current flows.
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daniel
post Jun 11 2002, 00:55
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QUOTE
Wow ! At last we know WHY silver is used in cables 


Yes, i know:evil: biggrin.gif (+a smiling bat)
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JonPike
post Jun 11 2002, 11:01
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QUOTE
Originally posted by Pio2001


Wow ! At last we know WHY silver is used in cables biggrin.gif 

In radio-frequencies applications (way above the audio range) skin efect can be a serious problem, overcome by silver plating to reduce resistance at the surface, where the bulk of high frequency current flows.


Ahhh.. cables and you.. One of the most Religious areas of Audiophiledom..

I come from an Electronics Engineering background.. and I think most of the beleifs are more Faith, Trust, and Mass Hypnosis.. (marketing with some Religon mixed in?) than real Science.

Some of the ideas actually have some merit.. but most are completly out to lunch.

For phono connections.. yes, you can spend hundreds just for the twisted pair that only goes from the cart, down the inside of the arm, and to the external cables. For the outside cables.. just some well shielded stuff would be the main thing..

Resistance? the imput impedence for MM cartriges is a set standard: 47K, (47,000 ohms) so if you had a really high resistance of 1 ohm, that would cause a loss of 1:47000.. not a big deal, even with millivolts of signal.

Grounding? a difficult subject.. but it boils down to: A. Make sure it has a good connection. B. Avoid ground loops. All cables will benifit from having a single end be the ground attachment point, that point being a single place, usually at the amp (or preamp). Since the chassis of the TT needs it too, that's why a separate wire goes from there to the amp... Actually, my Sony dosen't do this (shields are attached at the TT end) but dosen't seem to suffer from hum. When the ground wire is attached, anyway. Phono is more sensitive than most things, due to the huge gain of the preamp..

A conceptual thing: The Star Ground.. Meaning you have all your grounds connect together in ONE place.. (like the amp) they radiate out from there. Minimizes loops. Setting up your stereo gear like this helps prevent currents flowing in shields between different components. OTOH, a TT is single piece, with two channels.. getting currents flowing between L and R shouldn't happen.. so the sheilds being tied shouldn't be a big deal.. though the unshielded run thru the tonearm to the cart kinda requires the chassis be shielded, and THERE a separate ground to the amp is like a one side connected cable and prevents possible loops.

A test.. if you can, by putting your hand on and around the cables and connectors, cause audible hum.. you might think about upgrading them to a better shielded one, and or check the connectors for bad connections.. in the cable or where it plugs into your amp. If not.. you've probably got as good as you can get.

As for Silver wire.. in my Ham books, I read about someone spending lots of $$ getting a UHF transmitter's cavity silver plated.... and it made no measurable difference, cause it was "only" 432Mhz. (!!) If it was Microwave frequencies.. (in the Ghz range) it probably might have ben worth it. At Audio freqencies... hmmmm..
Silver's bulk resistance is only 10% lower than Copper, anyway..

Anyway, enough late night rambling..
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KikeG
post Jun 13 2002, 10:11
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The only sort of directionality in cables is the related to the shielding connection pointed by Pio. Any other supposed molecular properties of the cable conducting better in one direction and the like, are marketing BS. Cables are not directional in this way, simply because the electrical signal they carry is not directional, is AC signal. So any "directionality" in these cables would result in horrible distortion of the audio AC signal.

By the way, you can do your own tests of audibility of a cheap cable + soundcard as explained in this thread:

http://www.hydrogenaudio.org/forums/showth...=&threadid=2280
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fewtch
post Jun 13 2002, 17:06
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*AC* signal? AC is alternating current, meaning the current reverses polarity constantly. Do you mean "modulated DC," or do you really mean it's AC?


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Pio2001
post Jun 13 2002, 17:48
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It's AC, of course (=modulated DC by definition). On the waveform, the silence (0 Volt) is in the middle.



Here's a sinewave. The red line in the middle represents no current at all. Higher levels are positive voltage, and lower levels negative ones.

It represents as well a sound wave, or the AC current we use everyday.
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fewtch
post Jun 13 2002, 18:19
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So how would DC be represented on the graph, as a straight line always staying at the same level (above or below the midpoint)?


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Pio2001
post Jun 13 2002, 20:05
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Yes, the two horizontal dark blue lines could be DC, one positive, the other one negative.
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