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Old 10th June 2011, 11:44 AM   #1
dinck is offline dinck  Netherlands
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Default Seeking advice configuring XLR interconnects

Hi there,

I found this forum while googling for answers and have been visiting it for quite a time now. Fora present the combined wisdom of communities and i must say I am a little ashamed I haven't contributed so far, mainy because I feel a bit intimidated and I realise I know very little in this field of expertise. This, my first actual entry follows that path in that I seek advice.

I have recently upgraded my premap and CD player. I have had a Meridian 201 and 206DS combo for about 18 years but the transport and laser unit of the 206 have given away and can't be fixed because spare parts are o longer available. This makes me a little sad, I realy loved the sound but most of all I enjoyed the design an the build quality. Anyway, I replaced the set with a Meridian 502/508.24 combo. Newer components in the same league wouldn't fit my budget and quite frankly I don't like the design of the majority of most of them. I even favour the old Meridian set over the new one in this respect but I must say I didn't expect my new set to sound that much better.

And now let's go on topic.

The 502 and 508 are fully balanced while also offering balanced connectors. I would like to take full advantage of the balanced design and make my own balanced interconnects. I am considering using a 5 wire braided silver litz unshielded cable. Two pairs of wire would be twisted to make two double sized hot leads but I wouldn't know what to do woth the fifth remaining lead. Does any of you care to comment, specificly on the following questions?

1. Should a balanced interconnect also be shielded and is a unshielded braided cable less favourable?
2. If I go with the braided cable, would I need to connect the fifth wire to ground? And if so, should it only be grounded at the output end or at both ends? The comments on grounding the shield are not realy conclusive n this respect though grounding at both ends seems to win the vote...
3. And if that wold make any difference, while twisting the live wires shoud I twist the adjacent or the alternate wires?

Well, I am looking forwards to your replies.

franz
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Old 11th June 2011, 01:44 PM   #2
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In audio systems, star grounding systems are best because they don't have loops for AC power to induct ground currents around. One component in a system should be safety grounded, either the preamp or power amp, if separate boxes do the different functions. The grounding between the components should be done with a wire, with the shield used to keep out RF noise (radio frequency). In most cases, grounding the shield at one end only provides best results, but it is a cheap experiment, so try it both ways. CD player signals are high level and don't need a lot of protection, usually, unless the distances are long. More care must be taken with signals from magnetic phono cartridges, or tape heads (with electronics separate from the head).
The amount of twist in a twisted pair is critical to RF signals (like computer signals), but audio frequency signals are not very sensitive to this. Where there is a balanced signal in a pair, with signal going in one wire and return current going in the other, twisting them together defines the coupling and reduces interference from other currents. Usually the twisting is done before jacketing by the manufacture, and you have no choice afterwards of which wires are twisted. If you are making and jacketing your own cable, you have taken DIYaudio to an extreme.
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Last edited by indianajo; 11th June 2011 at 01:50 PM.
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Old 11th June 2011, 05:40 PM   #3
dinck is offline dinck  Netherlands
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Hello Indianajo,

I appreciate your comment but am afraid you misread my intention. The cable I am considering is a five-conductor braid, each conductor consists of silver litz and is teflon coated. The cable itself resembles the Kimber Kable KCAG which has three braided conductors. When I mentioned twisting pairs of wire that was obviously confusing, I meant twisting the bare ends of two conductors. Thus conductors 1 and 3 (or 1 and 2 in case of using the adjacent conductors) would be made to one live lead and conductors 2 and 4 (or 3 and 4) would be the second live lead. This woud leave the fifth conductor as a possible ground and if I understand you correctly I would have to connect this one to pin 1 of the XLR plugs at both ends.

Like the Kimber KCAG the braid would not be jacketed (hence unshieded), which would not be a problem since it's just a short run between CD and preamp. I understand braiding also rejects RF, and pairing two connectors of a braid would likely be even more effective. Isn't the whole point of balanced cables to keep out RF? So would an additional shield offer further advantages?

My present power amp only supports unbalanced signals. Were I to replace the amp (plans to build two monoblocks were the main reason I started visiting this site!) a shielded interconnect would indeed be favourabe as it woud require a quite long run. As you have pointed out, that would take DIY to a level I am not confortable with.

franz

PS. please excuse my typos, my keyboard is not very responsive so I occasionaly miss a character and I do not have an Engish spell check.
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Old 14th June 2011, 05:46 AM   #4
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Your post is all confusing, at least for me.
Do u intend to connect balanced output to unbalanced input?

If so, u should not do it.

Gajanan Phadte
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Old 16th June 2011, 03:32 PM   #5
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Hello Dink,


For a balanced interconnect use a balanced cable! If you like to use silver please do, Teflon insulation works fine and to my opinion does not influence the sound (like any good insulator / cable).

Don't use 2 conductors to carry a single signal, it will cost more and won't bring any improvement except for very long cable runs (@50+ M Rdc will come into play here, but also a lot of other considerations like capacitance of the cable).

Regarding the braid for RF rejection, look at the coverage of the braid, 100% is the best of course but anything down to 80% should be fine, your balanced / unbalanced input should reject any RF by design anyway (look at the CMRR of your balanced inputs this should be in order of 40 to 50 dB, also look at the frequency response of your input it will attenuate signals that are not in the audio band (0 - 100Khz or so) and this attenuation will increase with the frequency ).

If you want to go from balanced to unbalanced you can use the balanced "hot" pin and ground to connect to the RCA connector. Connect the braid only at the source (low impedance). Don't forget that most balanced interconnects work at a nominal level which is ~ 12dB higher than unbalanced (consumer) interconnects. You need to take care of this if your input can't handle the higher signal level (clipping).

Groetjes / best regards,

Mark
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Old 18th June 2011, 03:11 PM   #6
dinck is offline dinck  Netherlands
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Hello Mark, Gajanan,

thanks for your input. To make it clear, the interconnect is meant for a balanced output to a balanced input. XLR's at both ends, pins 2 and 3 carry the positive and negative signal of a single channel and pin 1 from the plug should be used as ground (as I understand connected at both ends, please do correct me if I am wrong!). The hot signal leads/conductors are identical in composition. In my understanding this makes a balanced cable, or am I wrong? Obviously I need two of these interconnects for the two stereo channels. The required length is 75cm each.

My Meridian 502 preamp is fully balanced, and has balanced as well as unbalanced inputs and outputs. For now there is no need for a longer interconnect from the preamp to the power amp, this connection is unbalanced output to unbalanced input so I my old interconnects still do the job.

I feel it is very difficult explaining what I mean by braided conductors. This link shows the cable I want to use. Sorry, I don't know how to upload images. I realise it gets confusing because the shield jacket is often refered to as braid, but in this case it would only be the 5 conductors (individualy teflon coated) woven in a fairly loose braid. So no braided shield and no further outer jacket.

The main reason I considered a 5-conductor braid over a 3-conductor braid was RF rejection, as well as the fact that commercial cable manufacturers often suggest more is better. Further consideration is a single conductor of my proposed cable only measures 0.4 mm, would that realy do for a line level signal? I found a similar, albeit finished, "reference" quaity XLR cable that consists of 9 0.4 mm silver conductors, though I couldn't find out if 8 af them are used as signal carriers and only one as ground, or 6 as signal carriers and the remaining 3 as ground. Reviews seem to suggest significant improvement, but judging on your answer, Mark, I shouldn't pay it too much attention.

Mark, you lost me mentioning Rdc and CMRR. It shows what an amateur I am in this field. But if I understand you correctly you would favour a braided shield, a jacket covering the actual conductors. Indianajo suggested the shield should be connected at one end, further investigation learnt this would preferably be done at the recieving end (in this case the preamp input side). Searching for braided shields I found copper ones, silver plated copper ones and even silver ones! Now I can't imagine this would be of any influence on shielding properties or on sound quaity, but correct me if I am wrong. Then there's the question whether or not the shield braid should have a tight fit around the conductors (on top of that some shielded cabes have the conductors embedded in plastic or rubber foam to fix them in their relative position). Apart from (or instead of) the braided shield some cables feature copper (or even mu-metal) tape wrapped along in a spiral. And then I didn't even mention the outer jacket (tubing) of the cable, either woven or solid. Manufacturers claim these all are factors to be considered as essential for the (sound) quality, but this brings me into voodoo-like territory I can't begin to grasp. Besides, even if this would have any influence on performance it would require endless experimentation to find an optimum. More importantly, as Indianajo pointed out this would take DIY to an extreme and I just want to keep it as simple as possible.

So to summarize, if I understand all correctly, in your oppinion I would be best served with a 3-conductor cable (problem there at the moment is the vendor I found only supplies 4- and 5-conductor cables). You would however add a braided shield. Then an outer jackt would also be needed for protection, I suppose a woven jacket would be appropriate. This would increase the complexity, but is still manageable.

I have to confess I find it a bit discouraging to realise how little I know and understand, it makes me wonder if it even makes any sense that I would want to make my own interconnects. Simply buying a confectioned cable now seems so tempting...

franz
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Old 18th June 2011, 07:30 PM   #7
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Why do you make it so complicated? Where did you get this 5 conductor thingy idea from?
This is for interconect on an installed audio system, I believe. Interconect wires less than a meter in length.
Use a twisted pair, 18 through 24 AWG stranded copper wire, no gold, platinum, silver or unobtainium plating needed, shielded. Use foil (cheaper and better than braid in interference rejection as it has better shielding coverage), braid is needed for live system as it is considderably more rugged to the abuse on stage.
Connect all 3 pins of the XLR: 1=shield, 2=+ or signal, 3=- or return. As all your equipment is on the same AC outlet a ground-lift is not required, but if you insist: Neutric has switches available that integrate beautifully into their inline XLR connectors
E
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Old 18th June 2011, 11:06 PM   #8
dinck is offline dinck  Netherlands
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Hi E

now there's a question that is easy to answer! I'm not shure though my answer will be either convincing to you or factual correct. Over the years I have been hearing quite a lot about audio cables, and I was often bewildered by the sky high asking prices. I know reviewers tend to exagerate, claiming to hear incremental nuances and presenting them as huge improvements. Quite a lot of grains of salt neded there, in my humbe opinion. Still, some of the hysteria must have rubbed off and some of the theories made sense, at least to me. However, I must admit the improvement of my newer Meridian set over the older one is considerably higher than my sceptisism would allow me to expect. The older set had raving reviews in its time and I have always loved it, finding it hard to believe a significant improvement was possible. And the newer set just proves the reviewers to be right, the sound is clearer, more open, spacious, just name the cliché's, that is using the unbalanced output and input. The balanced operation should even improve on this. So where does this leave me with my scepticism about cable reviews? My general understanding from these reviews is that silver cables are believed to be auraly superior. The braided design and the RF rejection was convincingly advocated by Kimber, albeit he uses a varistrand design (each conductor consisting of strands of different gauge).

So I now own a CD player and a preamp that both are considered high end while the cables I own are still my 18 years old entry level MTI's. I just felt I wanted a new set of high quality interconnects but am not willing to pay hundreds (or even over a thousand) of Euro's for them. And that was why I started exploring the possibility of making my own cable. Googling for silver cable I came across the mentioned 5-conductor cable and somehow it all seemed appealing. The costs are within reasonable limits, about 70 Euro's (about 100 USD) for two 1 meter runs. However, now it is starting to make less sense, hence the temptation to simply buy a confectioned cable.

I appreciate your suggestion but I don't see the fun part in using ordinary copper wire, I might then just as well go for an off-the-shelf cable. Using foil or tape as you suggest seems more work and would require at least a certain level of routine whereas a braided shield could easily be slipped over the conductors. So I think that would be my way if I'd persue this venture.

I doubt I will, I have done some more reading this afternoon and that just added to the confusion. The shield on pin 1 should idealy be grounded to chasis ground and not to signal ground if both ends are connected. So I guess I now should try and find out how the XLR's are connected internaly in my gear?

What have I got myself in to?

franz
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Old 19th June 2011, 04:10 AM   #9
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After considerable experimentation, these are the best balanced cables I have been able to make. They are superior in every important (audible) way to commercially available cables that cost ten times more than the materials required here.

XLR connectors: Vampire, not Neutrik.

Signal wire: 24ga OCC solid copper with teflon insulation, available from numerous vendors. Not silver unless you like etched, brittle, fatiguing highs, and definitely not silver-plated. A larger gauge wire will probably not yield better results.

Ground wire: almost anything that is slightly larger gauge than the signal wire. Solid, stranded, doesn't matter. Teflon insulation is a plus, but not essential.

Shield: none, unless you like compressed dynamics or have a radio transmitter in your basement.

Construction: wrap both signal wires in a spiral around small diameter (less than 1/4") teflon tubing, with each signal wire on opposite sides of the tube at all times. They should spiral around the center tubing at two inch or so intervals. There is no need to be precise. This should resemble the two strands of a DNA molecule, with the tubing in the center. Secure with heatshrink tubing or electrical tape at regular intervals along the entire length. Insert the ground wire into some sort of sleeve of insulating material, even if it's already insulated. You can use hollow cotton piping, more teflon tubing, or some other inert material. The only purpose this additional layer serves is to space the ground wire away from the signal wires. Wrap the encased ground wire around the pair of signal wires/tubing assembly in a spiral OPPOSITE that of the direction of the signal wire spiral. The ground wire will cross the signal wires at nearly a 90 degree angle. If it's less than that, it's still okay. Secure with heatshrink tubing or electrical tape at regular intervals along the entire length. You should now have a spaced, twisted pair with a spaced, opposite twisting ground wire around it.

Attach the connectors (including the ground wire to pin 1 at BOTH ends, and don't worry at all about the equipment's internal connections--they know what they're doing!) and mechanically secure the cable to them. The Vampire clamping mechanism is very secure by itself unless you like to throw your cables around or tug on the wires. I don't use a sleeve material because I don't move my cables around very much and they just sit there. Commercial cables must have a pretty sleeve to protect them from abuse and make them look to be worth more money.

No need for multiple conductors or fancy braids or shielding. This design will work very well, and I have not found a better conductor than OCC solid copper with teflon insulation.

Peace,
Tom E
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Last edited by madisonears; 19th June 2011 at 04:17 AM.
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Old 19th June 2011, 01:37 PM   #10
dinck is offline dinck  Netherlands
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Hi Tom,

thank you for your insights. I would not want to through a lengthy period of experimentation myself for a number of reasons. For starters I wouldn't have a clue where to begin! And secondly, while I don't mind spending some time I think experimenting would be so time consuming I wouldn't have any spare time to listen to the music since listening to the sound to evaluate the experment would obviously draw the focus from the music.

So I realy appreciate your suggestion, especialy since it's still easy to do and promisses to have aural benefits over affordable off the shelf interconnects. My initial thought was to buy the braided cable and just connect the XLR's, obviously a very simple DIY project. Somehow this has taken a new direction, teaching me a lot on the way.

The way you describe silver als conductor realy puts me off as I prefer a natural integrated sound. I haven't heard any silver cables myself and I was wondering what all the fuss was about. Thinking a bit further an analogy pops up in my mind. Recent video and photo technology (including the horrible glossy screens by Apple) also tends to be over-crisp and shows too much hard contrasts and saturation to my liking. At first sight it looks spectacular, but soon fatigue sets in. So out goes the silver and a warm (no pun intended) welcome to copper! Tou have saved me quite some money there too.

There are some things I yet do not understand, but I would not question them.

I have always thought that more conductive material was better, understanding the importance of gauge (skin effect amongst others) I would presume doubling or even tripling the amount of conductors in your construction would help the electrcal flow. What I can think of now is that the narrower spacing between the conductors and the resulting interaction could be critical. (This notion also lead to my question about the configuration of a 5-conductor cable.) And then again, this could be countered by spiraling them around a larger diameter central tubing. I think I'd just like to understand some principles of interaction between conductors. Any comment?

I am a little surprised by your observation that the ground wire should be larger gauge than the signal wires as I have always presumed ground was uncritical to the actual sound. But i will take your word on it.

I hadn't yet heard of Vampire XLR's. A Google search lead me to vendors with a wealth of choice and I have seen some very pretty ones, notably from Oyaide en Xhadow as well as absurbly expensive ones (how about a pair of Bocchino Audio for USD 895?!!!). Even if interconnects are out of sight I am a bit of a sucker for nice design and clean appearance. For looks sake I would therefor add a sleeve to your design, i hop you won't mind. But i will take your advice on the connectors, the Vampires look well enough...

So thanks again, your comments have been very helpfull and have showd me the way to go. There's just one final question left. Can you roughly indicate the required length of the conductors needed to make a 1 meter interconnect?

Kind regards,
franz
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