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Turntable cables question

post #1 of 23
Thread Starter 
This might be a dumb question, but is there anything special about the L-R cables that connect the turntable to the phono stage? I have some standard L-R cables that are far better quality than the one provided by the TT manufacturer, and I'd like to swap them out and run a separate electrical wire for the ground between the TT and preamp. What I don't know is if the TT cables are a different impedance (or something).

- Mark
post #2 of 23
Not a problem.
post #3 of 23
What you are proposing to do will do no harm. There's no reason to believe it will do any good either, unless there's something demonstrably wrong with the existing cord.
post #4 of 23
Thread Starter 
Thanks to both.
Quote:
Originally Posted by mcnarus View Post

What you are proposing to do will do no harm. There's no reason to believe it will do any good either, unless there's something demonstrably wrong with the existing cord.

Yeah, I was afraid of this turning into "The Great Ongoing Cable Debate". smile.gif That's not really where I'm coming from - I don't believe in spending tons of money on cables. But the provided one seems especially chintzy - I even had to squeeze the ends to get a firm fit. I occasionally get faint static, which is fixed by a bit of a twist to re-seat the thing.

Thanks again,

- Mark
post #5 of 23
Quote:
But the provided one seems especially chintzy - I even had to squeeze the ends to get a firm fit. I occasionally get faint static, which is fixed by a bit of a twist to re-seat the thing.
Well, that's definitely a reason to change cables.
post #6 of 23
There are two qualities you need to consider in a moving magnet cartridge system: capacitance and shielding. The first is because the capacitance of the cable will react with the other reactive elements of the system to affect HF response of the cart (see here), and shielding, because the relatively low signal level and high impedance of the system make it more susceptible to pick up external noise/signals.
post #7 of 23
^^ Completely agree with the previous post. A turntable is one component that justifies a high quality cable due to the low signal levels of the cartridge output. I've been a fan of moving coil cartridges for many years now which tend to have really low signal levels. The careful selection of a TT to phone pre-amp cable made a noticeable difference over a set of generic LR cables.
post #8 of 23
Quote:
Originally Posted by twowheelin View Post

^^ Completely agree with the previous post. A turntable is one component that justifies a high quality cable due to the low signal levels of the cartridge output. I've been a fan of moving coil cartridges for many years now which tend to have really low signal levels. The careful selection of a TT to phone pre-amp cable made a noticeable difference over a set of generic LR cables.
High quality does not equal high cost though. I was thinking of Mogami/Canare/Belden mic cables which are modest in cost and I have used many times. Better still is to get the phono pre as close as ispractical to the TT.

For MC, shielding is all that's really important as the impedances are too low for capacitance to be an issue like MMs.
post #9 of 23
Thread Starter 
I had a 3 foot AR Pro Series audio L-R that I swapped out the stock cable for, and it works well. As A9X-308 (?) noted, I have my phono stage immediately below my TT.

Another dumb question though, why does one need to use the grounding cable on turntables, when I don't need it on any of my other equipment?

- Mark
post #10 of 23
Hi Mark,
Quote:
Originally Posted by chileboy View Post

. . . why does one need to use the grounding cable on turntables, when I don't need it on any of my other equipment?
Not a dumb question. It's mainly because of the low level of the signal, which requires substantial amplification by the phono-preamp. It doesn't take much to couple 60Hz hum into such a low-level signal, and the hum is then amplified by the preamp.

Here is the situation with my setup: Internal to the turntable, the cables connect to the cartridge and nothing else. There is no grounding to the audio wiring, and because the turntable has a two-wire plug, the metal of the turntable, like the tone-arm, is not chassis-grounded. If I don't hook up the ground wire, I hear a slight 60Hz hum, from the AC power coupling into the audio. If I then touch any metal part of the turntable, the hum gets load enough to shake the house. If I hook the ground-wire to my preamp, all hum goes away, as the metal of the turntable is now grounded.

The only way the metal parts of my turntable are grounded is through that ground wire. If the turntable had a three-prong plug, then a separate ground-wire might not be needed, but then you would have the possibility of a ground-loop, which would be fixed by removing the third prong and adding a ground-wire. So that's the best way to do it.

You could also ground the metal of the turntable using the audio-cable shield, but then, if there is a ground-potential difference, an AC current would flow through the shield, which would again induce hum into the signal.
post #11 of 23
Moving Magnet phono cartridges require a ground cable. Been that way for a few decades. smile.gif
post #12 of 23
Quote:
Moving Magnet phono cartridges require a ground cable.
They require a ground, but not every turntable grounds the cartridge through a separate cable. It's also possible, as Mark H. notes, to ground through the shield. Probably not the best approach, but it saves a penny or two.
post #13 of 23
Thread Starter 
Quote:
Originally Posted by MarkHotchkiss View Post

It's mainly because of the low level of the signal, which requires substantial amplification by the phono-preamp. It doesn't take much to couple 60Hz hum into such a low-level signal, and the hum is then amplified by the preamp.

Here is the situation with my setup: Internal to the turntable, the cables connect to the cartridge and nothing else. There is no grounding to the audio wiring, and because the turntable has a two-wire plug, the metal of the turntable, like the tone-arm, is not chassis-grounded. If I don't hook up the ground wire, I hear a slight 60Hz hum, from the AC power coupling into the audio. If I then touch any metal part of the turntable, the hum gets load enough to shake the house. If I hook the ground-wire to my preamp, all hum goes away, as the metal of the turntable is now grounded.

The only way the metal parts of my turntable are grounded is through that ground wire. If the turntable had a three-prong plug, then a separate ground-wire might not be needed, but then you would have the possibility of a ground-loop, which would be fixed by removing the third prong and adding a ground-wire. So that's the best way to do it.

You could also ground the metal of the turntable using the audio-cable shield, but then, if there is a ground-potential difference, an AC current would flow through the shield, which would again induce hum into the signal.

Thanks Mark, all of that makes sense. I was curious because most (maybe all) of my components only use a two-prong plug, so it would seem they would need some kind of ground as well. Although, now that I think about it, my power amp probably has a three-prong, so maybe everything else is grounding through that via the interconnects?

Anyway, I'm guessing from what you said that the difference is the very low-level of the signal from the turntable, and if any component required that much amplification, grounding could become an issue.

Thanks again!

- Mark
post #14 of 23
Quote:
Originally Posted by mcnarus View Post

They require a ground, but not every turntable grounds the cartridge through a separate cable. It's also possible, as Mark H. notes, to ground through the shield. Probably not the best approach, but it saves a penny or two.

If the turntable has a ground wire (typically green), you have to use it. wink.gif
If the turntable doesn't have a dedicated ground wire, then it probably uses a ceramic cartridge or....... is a very inexpensive (crappy) turntable if it uses a shield for a MM cartridge (like some TT's that came out a few years ago with built-in/switchable pre-amps).
post #15 of 23
Quote:
If the turntable has a ground wire (typically green)
Hardly typical, in my experience. How many turntables have you ever seen?
Quote:
If the turntable doesn't have a dedicated ground wire, then it probably uses a ceramic cartridge or....... is a very inexpensive (crappy) turntable if it uses a shield for a MM cartridge (like some TT's that came out a few years ago with built-in/switchable pre-amps).
I gather you are unaware that Rega turntables come without ground wires. Just as an example.
post #16 of 23
Okay.... I've been seeing turntables starting around 1962. But, if you want to argue about the typical color.... I couldn't be bothered, no matter your experience. rolleyes.gif
Again, if the turntable has a ground wire (no matter the color).......... you have to use it!
post #17 of 23
The turntable should always have a separate ground wire from the metal chassis or arm base of the turntable to the metal chassis of the main preamp or integrated amplifier. The size of this conductor is not important; 18 or 20 gauge is typically used.

This is a chassis ground, whereas the outer cable conductor is a SIGNAL ground, which carries the return signal current back to the cartridge. The two should be
kept separate to prevent hum and noise.
post #18 of 23
Quote:
Originally Posted by chileboy View Post

This might be a dumb question, but is there anything special about the L-R cables that connect the turntable to the phono stage? I have some standard L-R cables that are far better quality than the one provided by the TT manufacturer, and I'd like to swap them out and run a separate electrical wire for the ground between the TT and preamp. What I don't know is if the TT cables are a different impedance (or something).

Someone said something about running turntables since 1962. How about since 1960, and still have one?

Bottom line is that if there is adequate shielding and electrical continuity, what you have is fine.

Even more to the point, are you having problems with hum or interference pick up? By interference pickup I mean something like a nearby radio station or police cars rolling by your house talking on their radios?

There's an old adage that goes something like "If its not broke, don't fix it". That is just common sense.

This is especially true of grounding wires. If you aren't having problems with hum, it is even possible that adding a ground wire can make things worse.

I'll even get in your face and ask you how you know that the wires you propose to use are really technically better? I wouldn't say that unless I cut the wire and stripped it and looked at the center conductor, the insulation, and the shielding. One never does that unless you want to scrap the wire or are prepared to put a new connector on it. How's your soldering? Some wires look great, but all you can see is the outer insulation, and that's all you have to base your judgement on unless you want to go deeper.

Depending on what cartridge you have, there are some things you can do what will improve sound quality.

How is the cartridge mounting geometry? Have you checked cartridge geometry with a protractor or gauge?

http://www7a.biglobe.ne.jp/~yosh/alignment_gauges.htm

Have you checked tracking force with a stylus tracking force gauge?

http://www.bhphotovideo.com/bnh/controller/home?O=&sku=229192&is=REG&Q=&A=details

Have you checked out cartridge capacitive loading with a test record and frequency response measuring hardware?

http://www.tnt-audio.com/sorgenti/load_the_magnets_e.html
post #19 of 23
Quote:
The turntable should always have a separate ground wire
Tell it to Rega.
post #20 of 23
Thread Starter 
^ Well, as I said Arnold, I had no intention of getting into the never-ending cable debate.

You must have missed where I said the main issue was that the supplied cable did not fit tightly and I would sometimes get static unless I rotated one of the RCA plugs. I just wanted to be sure that using any good-quality audio cable would be fine. I'm not a believer in high-priced exotic cables - just quality cables - and I believe I made that clear in another post, so no need to "get in my face", as you said.

I did not mention it because it was not germane to my question, but since you ask, no I haven't been at this as long as you - however, I have some experience and I've already properly aligned my cartridge (with an arc protractor), adjusted the tracking force with a proper stylus gauge, checked the azimuth, and yes, I use the Hi-Fi News Analogue Test LP to check everything. My only issue was the static in the cable.

Thanks for the input,

- Mark
post #21 of 23
Quote:
Originally Posted by chileboy View Post

^ Well, as I said Arnold, I had no intention of getting into the never-ending cable debate.

You must have missed where I said the main issue was that the supplied cable did not fit tightly and I would sometimes get static unless I rotated one of the RCA plugs.

I missed that, but the usual fix for loose RCA's involves crimping the outer sliding contacts on the RCA plug with a pliers to tighten it up.
Quote:
I just wanted to be sure that using any good-quality audio cable would be fine. I'm not a believer in high-priced exotic cables - just quality cables - and I believe I made that clear in another post, so no need to "get in my face", as you said.

I did not mention it because it was not germane to my question, but since you ask, no I haven't been at this as long as you - however, I have some experience and I've already properly aligned my cartridge (with an arc protractor), adjusted the tracking force with a proper stylus gauge, checked the azimuth, and yes, I use the Hi-Fi News Analogue Test LP to check everything. My only issue was the static in the cable.

Sounds like you have all of the rest of that stuff under control.
post #22 of 23
Thread Starter 
Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by chileboy View Post

^ Well, as I said Arnold, I had no intention of getting into the never-ending cable debate.

You must have missed where I said the main issue was that the supplied cable did not fit tightly and I would sometimes get static unless I rotated one of the RCA plugs.

I missed that, but the usual fix for loose RCA's involves crimping the outer sliding contacts on the RCA plug with a pliers to tighten it up.

Yeah, I did that actually, but perhaps wrongly it just gave me some doubt as to the general quality of the cable, and I'm just a bit of a perfectionist (I'll avoid the anatomical reference) I guess. Since, like everyone else, I have boxes of good unused cables, I just thought I'd swap it for a known quality cable. Plus, there's always more to learn, which is why I ask. This thread taught me a few things, which is good.

Thanks,

- Mark
post #23 of 23
Quote:
Originally Posted by chileboy View Post

Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by chileboy View Post

^ Well, as I said Arnold, I had no intention of getting into the never-ending cable debate.

You must have missed where I said the main issue was that the supplied cable did not fit tightly and I would sometimes get static unless I rotated one of the RCA plugs.

I missed that, but the usual fix for loose RCA's involves crimping the outer sliding contacts on the RCA plug with a pliers to tighten it up.

Yeah, I did that actually, but perhaps wrongly it just gave me some doubt as to the general quality of the cable, and I'm just a bit of a perfectionist (I'll avoid the anatomical reference) I guess.

RCA cables do vary in terms of how many insertions & pulls they will take before they loosen up. Since their usual lifetime duty cycle involves doing that a relatively small number of times, its usually not much of a problem. But as engineer I can appreciate cables that take the proverbial licking and keep on sticking.
Quote:
Since, like everyone else, I have boxes of good unused cables, I just thought I'd swap it for a known quality cable. Plus, there's always more to learn, which is why I ask. This thread taught me a few things, which is good.

It's that known quality part that often leads me into surprises. ;-)
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