Popular Post JohnSwenson Posted April 20, 2017 Popular Post Share Posted April 20, 2017 There has been a lot of posts recently in other threads about making your own DC cables for LPS-1, JS-2, Y adapters etc. I'm going to attempt to give some theory behind DC cables and CA and some hints for making your own, and some results of my own experience. So what is the big deal, DC is, well, DC! Resistance should be the only thing that matters, right? Wrong! Particularly for power digital circuits some AC issues actually do make a big difference. This is due to the fact that the load current of most digital devices is not constant, it varies all over the place, and can do so very quickly. This rapidly changing load current causes a voltage to develop across the inductance in the cable. No matter how good the regulator in the power supply is this noise will still be there. This means that both resistance and inductance of the cable matter. Cable capacitance is a good thing, but the ranges available in cables have a very small effect so so you can pretty much ignore the cable capacitance. Are there "cable parameters" that DON'T matter for a DC cable? Yes, anything that primarily affects distortion is not an issue, such as stranding vs solid core, conductor material and plating. The difference in resistance between silver and copper does produce lower resistance than copper, but just making the copper conductor slightly thicker does the same thing. Thus I do not consider the vastly higher price of silver worth it. The net result is that stranding doesn't matter, OCC etc doesn't matter, dialectric has extremely small effect. So what DOES really matter? The wire gauge determines the resistance and the geometry of the wires (how they are arranged in the cable) makes a HUGE difference in the inductance. So things to optimize for, thick wires and use the proper geometry. The geometry is actually far more important than the wire gauge, although you don't want to go with really thin wires either. There are 4 common geometries in use in DC cables: parallel conductors (zip cord) coax twisted pair starquad They are listed in decreasing inductance, zip cord has about 10 times the inductance as starquad for equivalent gauge. Coax and twisted pair are pretty much the same at about 1/3 the inductance of zip cord. All can be shielded or not shielded. The shield does not really make things better for most applications of DC cables, but if it is done wrong (which is extremely prevalent) it can make things worse. Thus I recommend using unshielded cable for most situations. I hope from the above you come to the conclusion that using starquad is a good thing when making your own DIY DC cable. So what is starquad? It consists of four conductors, the whole group of which is twisted in the cable. This is NOT two twisted pairs. They are not woven or braided, the four conductors are arranged in a square. Diagonally opposite conductors are connected together at both ends of the cable. That is it, not very complicated. There are many articles on the net covering starquad with nice pictures. (sometimes it is called star quad, sometimes star-quad, they are all the same thing) So what is special about starquad? Well of course you have two wires in parallel which halves the resistance, but the big thing is the magnetic field, it forms in such a way that the inductance is about 3 times lower than coax or twisted pair, AND it produces an inherent very good shielding effect, without using a shield! So to make your own starquad cable you need a cable with 4 conductors, with the whole thing twisted, preferably unshielded. There are many of these on the market. They do not have to be specifically marketed as starquad. Many cables that say "starquad" have wires with only two colors, diagonally opposite wires have the same color, that makes it easier to figure out which ones to connect together. But cables with different colors for all for wires also work well, you just have to figure out which ones are diagonally opposite each other. So what gauge to use? A 24 gauge starquad microphone cable is probably too small, and a 14 gauge speaker cable is probably going to have wires that are impossible to connect to the barrel connectors most components use. So somewhere in between is probably a good choice, 20 or 18 AWG wires are probably the sweet spot. Belden 8489 and West Penn 244 are 18AWG 4 conductor unshielded cables that work very well. Canare makes a starquad speaker cable called 4S6 which has 20AWG wires which should be a very good choice as well. Alex likes to use a cable with a shield which I think just makes things more complicated than they need to be. If you want to make your cable without soldering anything there are barrel plugs with screw terminals available at many places. These terminals will accept a single 18AWG wire nicely, but it gets very tricky to put two 18AWG wires into each connector (which is what you have to do for starquad). The 20AWG 4S6 might be a better choice when using these. If you want to make a Y cable where you put TWO cables into one plug, you may just barely be able to get 4 20AWG wires into each connector. Last night was the first time I was actually able to try some of this myself. Since I am on the road now without my soldering equipment I decided to try a starquad cable with the screw terminals. My entire setup right now is an LPS-1 powering a SqueezeBox Touch (SBT) with Senheiser phones plug in to the SBT. The current setup used a simple DIY 16 AWG zip cord cable with soldered on barrel plugs. So I found a small amount of 244 on ebay and a bunch of screw terminal connectors on Amazon. They were all here yesterday. Then started the fun, the two 18AWG wires do NOT fit well in those screw terminals. Every time I pushed them in a strand or two would not go in and curl off to the side shorting out to the other terminal. I had to try it about seven times to get all 4 wires properly inserted into the plug. The wires are pretty stiff so I had to really tighten those screws down tight to keep them from pulling out. It only took five tries on the other end of the wire. I finally got it together and plugged it in, WOW this was a big improvement! I thought this system sounded amazing, but with this DC cable it was dramatically improved. And that less than 10 dollars! Next I'm going to try the 20AWG 4S6 cable and see how that sounds. John S. Encore, Cornan, Duke40 and 6 others 7 2 Link to comment
JohnSwenson Posted April 21, 2017 Author Share Posted April 21, 2017 1 hour ago, Middy said: Haha I missed the locking point. Thanks. May be john posts a picture of his mini test cable..?? Here you go! Middy 1 Link to comment
JohnSwenson Posted April 21, 2017 Author Share Posted April 21, 2017 7 hours ago, Ralf11 said: What is the inductance in the cable, and how does the AWG affect it? Do you have a histogram or anything? I don't have the test equipment with me to measure it right now (I have to wait until the lab is setup in the new house). I cannot find any simple equations for these things. Actual formulas for inductance of the different implementations turn out to be very complex, I could not find anything that wasn't several pages of arcane math. The best I could do is the rough ratios between geometries assuming everything else is the same. John S. Daudio 1 Link to comment
Popular Post JohnSwenson Posted April 24, 2017 Author Popular Post Share Posted April 24, 2017 5 hours ago, austinpop said: Btw - looking forward to John's report on the Canare. OK, the Canare 4S6 came in yesterday. It is MUCH easier to work with than the West Penn 244, the conductors are 20AWG and much finer stranding. It is significantly more flexible as well. Doing a single starquad into the screw terminal plugs is a piece of cake with this cable. I was even able to do a Y-cable with it. That was significantly harder to do, but it did work. Even the Y-cable was easier than the straight cable with the 244. Now on to the sound. I was expecting that do to the thinner conductors it might not sound quite as good as the 244. Well far from it! This cable with the 4S6 sounds better than the 244. The SBT when fed power from an LPS-1 and this starquad cable is producing some of the best sounding music I have ever heard! This is mind blowing that the $200 SBT when fed good power is transformed into such an incredibly good sounding device. Note this is only when plugging the headphones directly into the SBT, the line outs don't sound any where near as good. Given the above I heartily recommend the Canare 4S6 starquad cable for making DC cables. John S. austinpop and Middy 2 Link to comment
JohnSwenson Posted April 24, 2017 Author Share Posted April 24, 2017 2 hours ago, austinpop said: John, Now you have us really excited! Can't wait to try it. Sorry, noob DIY question - from the pictures, it looks like there are 2 red and 2 white wires? And these are what connect together? The 4S6 has a solid red, clear red, white and clear wires. The two red wires are connected together and the white and clear are connected together. John S. Link to comment
JohnSwenson Posted April 24, 2017 Author Share Posted April 24, 2017 6 hours ago, Em2016 said: Hi John, will the DC plugs with screw-in terminals fit next to the USPCB, for both the USB REGEN and ISO REGEN? Those DC plugs are quite large compared to a normal cable plug and may clash with the USPCB or even clash with the cheap hard adapter, side by side? Cheers Yes the DC plug with the screw terminals fits nicely on any of the REGENs with the USPCB. You are going to have to bend the wire down very sharply if you want to avoid hitting the device the USPCB is plugged into. This is assuming you are using the USBCB on the upstream side of the REGEN (which is the side with the DC in jack. If the USPCB is on the downstream side (connected to the DAC) then there is no issue since the only thing on that endplate is the downstream USB jack. John S. Link to comment
JohnSwenson Posted April 24, 2017 Author Share Posted April 24, 2017 24 minutes ago, Forehaven said: Does anyone know if there's a max. recommended length per DC cable? There is no such thing, other really gross things like "a mile is probably too much". The longer the cable the more resistance and inductance you have, thus it is probably good to keep the cables aa short as possible. Thus if you are using an LPS-1 you should have it close to the load. John S. panasonicst60 1 Link to comment
JohnSwenson Posted April 26, 2017 Author Share Posted April 26, 2017 3 hours ago, sockpit said: Slightly off topic but star quad related: my speaker cables our diy, and made from 14 awg, four strand audio quest speaker cable design for in-wall installations. when terminating them, I paired them together (since I'm not biwiring). Problem is I didn't pair them diagonally. now so far as I can see these four wires are not twisted at all, but just run parallel inside the casing. Would redoing the pairing so they are diagonally paired make any difference theoretically with speaker wires of this sort? thanks. Yes, the star quad configuration is NOT just about shielding, the big reason for using it in low impedance circuits such as DC cables and speakers is that the inductance is much lower with starquad. So even if there is no twist, pairing diagonally opposite conductors will significantly reduce inductance of the cable. In most circumstances this will improve the sound through the speakers. John S. sockpit 1 Link to comment
JohnSwenson Posted April 27, 2017 Author Share Posted April 27, 2017 Gold plating for power connectors is not necessarily a good thing. If the system is energized when you plug it in, a small spark is generated when they connect. This has enough energy to vaporize the gold plating where the 3 hours ago, R1200CL said: I have found a Chinese manufacturer that may be willing to either offer these power cables we need using the suggested Canare cables. Free shipping. It will either be a group-buy, or included in his product line. Length I'm not sure, but I think most is interested in short lengths. Maybe 20 cm. (0,65 ft). I expect a very nice price ? Unless he as well has to use expensive plugs. I hopfully will know more later in a couple if days. Just make sure they know to connect diagonally opposite conductors. Thanks, John S. Middy 1 Link to comment
Popular Post JohnSwenson Posted May 3, 2017 Author Popular Post Share Posted May 3, 2017 4 hours ago, R1200CL said: The Chinese manufacturer will make a test sample with the new Oyaide plugs with the Canare 4S6 cable, as he think this is doable. I'm not so sure he is right, so this is very nice of him to do. Probably ready during weekend. Will post pictures then. I'm trying to convince him to sell directly to end user. But I think I will have to make a poll or a spreadsheet in order to convince him there is enough buyers. (Of cause he does not like to waste money on the expensive Oyaide plugs). I must say I like these plugs as well. They should even be able to do a shielded cable from Canare. And then the right way is to have open shield in one end. Actually the end where your consumer (Microrendu or ISO regen) sits. I'm thinking about having him making Ethernet cables as well. Possible with the best plugs available and a Belden cable Open shield in one end as well. That's why you put direction on cables. The open open shield at one end is NOT the right way to do it. The last time I tried to bring this up I was thrashed by a large number of very angry people (I had no idea shield connection was such an emotional topic for so many people) so I am loath to bring it up again. Part of the problem is that I have no test equipment right now so I can't PROVE it. At least for the DC cables an unshielded starquad is better than one with improper shield. I have to make up my mind whether I want to talk about proper shielding at this time or not. John S. Middy and zerung 2 Link to comment
Popular Post JohnSwenson Posted May 5, 2017 Author Popular Post Share Posted May 5, 2017 OK here it is: cable shielding, how to make it work and how almost all cables have it wrong. The first important question is, what is electrical shielding and how does it really work? Lets look at the infamous "Faraday cage". For this discussion it is a metal box, with all sides well electrically connected (no gaps). Shielding means that electrical fields outside cannot be sensed inside. Conversely electrical fields inside cannot be sensed outside. So how does this work? When an electric field from the outside world impinges on the box it causes the electrons in the metal to move, this rearrangement of the electrons creates an electric field inside the metal which exactly counteracts the external field, thus the field is essentially stopped at the periphery of the box. The important aspect here is the part "electrons in the metal move". What are moving electrons called? Current. In order for current to flow there has to be a loop. Current will not flow unless there is a loop. In the case of the Faraday cage, the loop is the whole cage. Lets say an electric field impinges on a side of the box, this causes a current flow that goes all the way around the box back to where the field impinges on the box. If the sides are not electrically connected to each other the current cannot flow, thus the electrons cannot move, and the canceling electric field does not get setup, thus no shielding. It turns out that for AC electric fields it is a little different. Some current can flow due to capacitances between conductors. The electrons can move a little bit one way, then a little bit back. If the frequency is high enough the back and forth movement, which is charging and discharging the capacitance is sufficient for shielding. For a given capacitance the lower the frequency the less effective the shielding. The electrons start moving which charges the capacitance, then stop moving when fully charged, they don't do the full movement necessary to produce the canceling field. So what about shielded cables? I hope is now obvious that for shielding to be effective there needs to be a conductive path from one end of the shield to the other. If there is not such a path the only shielding that is going to happen is for high frequencies due to cpacitances involved with the shield. The best way for the shielding to work properly is a separate wire connected to each end of the shield. This is sufficient for shielding from DC to very high frequencies. Note the shield does NOT have to be connected an earth ground, the "ground" of the circuit at either end, or any thing else for that matter. A cable with a shield the is not connected to anything else except itself (ie a separate wire from one end to the other of the shield) will be highly effective in shielding what is inside. Where does this wire need to go? It can be either inside or outside the shield, but if it is inside it can couple to the signal wires inside, so it is usually best to have it outside the shield. Note it has to be insulated from the shield except for the ends where it connects to the shield. It should intersect as little of the external field as possible so it should NOT be tightly spiraled around the cable. Just running along side the shield is best, although a very loose spiral (say one turn per foot) is almost as good. So some ramifications of this: The traditional "connect the shield to one end and let the other end float" is not good, it does not allow a loop so shielding does not happen very well. If you add the external wire connected to the shield at both ends, then you CAN connect one or both sides of the shield to the signal ground or some other ground, but you don't NEED to for effective shielding. You will find that in many cases leaving the shield completely disconnected from the rest of the circuit is the best way to go, you get the benefit of properly working shielding without any interaction of the shield with your system. You may wind wind up with static charges on the shielding so a resistance from the shield to ground may be useful in some cases in order to dissipate static charges. So how come nobody does this? I don't know. My only guess is that cable shielding has been going on long before the actual mechanism for shielding was worked out, thus by the time it was understood, cable shielding was "standard" and nobody ever even thought about analyzing it based on an understanding of how shielding actually works. But shouldn't the big companies know about this? It seems they don't. I have read several app notes from Belden that state that shielding is only effective at high frequencies, at audio frequencies and power supply frequencies (60Hz etc) it is totally ineffective. Audio people are the only ones that seems to at least empirically know about this. Remember phono cartridges and preamps, there is a little green wire that goes from the "ground jack" on the preamp to the tonearm. Everybody assumes that this is to "ground the cartridge" but what it really does is provide a loop from one end of the interconnect shield to the other, it has nothing to do with whether it is "grounded" or not. So if you have (or had) a turntable you were actually taking advantage of this without realizing it. So there you have it, shielding DOES work, but only if you provide a path from one end of the shield to the other. This is effective even if you don't connect the shield to anything else. John S. mozes, Michael-Elijah Audio, Confused and 19 others 15 4 3 Link to comment
Popular Post JohnSwenson Posted May 5, 2017 Author Popular Post Share Posted May 5, 2017 8 hours ago, pl_svn said: actually there is a well known manufacturer using this kind of shielding in their most expensive cables but as far as I understand it... they're also applying some "current" (using a dedicated battery, I believe) to the "shielding wire" I looked at the AQ DBS system it is not the same thing. There is a separate wire in the center of the cable, but only one end is connected, to the + side of a battery. It is not connected to the shield at either end. Now someone COULD take this cable and connect both ends to the shield, which would provide effective shielding, but again it is near the signal wires which could cause problems. I also looked at NDS, which doesn't do it either, it has extra shields over the inner shield which are supposed to dissipate RF, but they, as far as I can tell, are not electrically connected to anything. If they just used my approach they wouldn't need the extra shields. John S. pl_svn and Middy 2 Link to comment
JohnSwenson Posted May 7, 2017 Author Share Posted May 7, 2017 7 hours ago, octaviars said: This cable that goes along outside of the sheild will it matter how thick it is? My thougt is to hide a small wire under the blackmesh nylon braid so it is not visable and connect it to the sheild in the powerplugs. What is your thoughts on this @JohnSwenson So far I have been using 24AWG wire for my tests and it has been working extremely well. As far as I can tell there are two issues: long length wire and very high frequency isolation. The 24 has worked well for the short cables I have built (up to 6ft), For really long ones you may need to go with thicker wire, but I have not done any experimentation on that so I really don't know for sure. For isolating very high frequencies (say gigaHz stuff) the inductance of the wire is probably very important, so this tends to point to thicker wire, but there may be many issues at hand there, I would have to delve much further into that before I could make a recommendation. John S. Link to comment
JohnSwenson Posted May 7, 2017 Author Share Posted May 7, 2017 5 hours ago, Forehaven said: Is that stranded copper wire John Yes it was stranded, but I don't think that makes any difference. Although to be fair I have not explicitly tested that. John S. Forehaven 1 Link to comment
JohnSwenson Posted May 7, 2017 Author Share Posted May 7, 2017 5 minutes ago, Michael-Elijah Audio said: I didn't - I used the Response 4 wire speaker cable with an external expandable shield from here: http://www.vt4c.com/shop/program/main.php?cat_id=22&group_id=3 Also - not sure why some are concerned about hiding the loop wire - from my understanding of JS's recipe - it's best not to have the loop wire touching the shield more than the connection points - surely by have it concealed in an outer sleeve, it will be much closer than is ideal I think R1200CL's idea of using Canare shielded star quad is a good choice Michael The wire should electrically connect only at the ends of the shield. The only other constraint should be that it does not intersect the original electric field very much. So NOT a tight helix around the shield, laying right next to the shield is fine as long as the diameter of the wire is small compared to the diameter of the shield. The insulation of the wire can touch the shield, again as long as it is significantly smaller diameter than the shield. Doing so and adding a non-conductice wrap is perfectly fine. John S. Middy 1 Link to comment
Popular Post JohnSwenson Posted May 7, 2017 Author Popular Post Share Posted May 7, 2017 48 minutes ago, R1200CL said: I suppose the shield wire should be hidden inside a sleeve that cover the whole cable ? Use his Canare 4S6S shielded cables he already have in stock I suppose ? Maybe add JSSG to an USB cable as well then ? And try to add shielded USB plugs as well, if they exist. For a DC cable remember that the resistance DOES matter and that starquad is already highly inherently shielded. Thus using un-shielded 4s6 is almost guaranteed to sound better than 4S6S with properly connected shield. John S. Cornan, Forehaven and R1200CL 3 Link to comment
JohnSwenson Posted May 7, 2017 Author Share Posted May 7, 2017 11 minutes ago, tboooe said: So John, is shielding a star quad cable even worth it for long runs? Or are you saying that as long as we are using star quad there is no need for shielding? Properly shielded starquad is useful in situations with small signals such as microphone cables or phono cartridges. For line level interconnects it is also probably useful. For speaker cables or DC cables it is pretty much useless (it doesn't hurt, but you don't get an extra advantage for your trouble) So for DC cables I would not even bother of course as long as you are using a starquad geometry. Whatever you do, for a DC cable, do NOT go with thinner conductors JUST to get shielding, that is the wrong trade off to make. John S. Link to comment
JohnSwenson Posted May 8, 2017 Author Share Posted May 8, 2017 55 minutes ago, tboooe said: Got it...the shielded star quad is a different model L-4E6S, which I think is basically the 4S6 with a shield right? It looks like awg is a bit smaller though i dont think it will make a difference for our application. I have not given up. I emailed the vendor but have not heard back. If I dont hear back I will try to make a shielded version myself and compare against the normal 46S. Actually they are quite different. 4E6S is a microphone cable, it has 24AWG conductors, the 4S6 is a speaker cable with 20AWG conductors, that is quite a big difference between conductor sizes. The shielding is not worth the dramatically thinner conductors in my opinion. John S. Michael-Elijah Audio 1 Link to comment
JohnSwenson Posted May 11, 2017 Author Share Posted May 11, 2017 1 hour ago, Middy said: @JohnSwenson I know it's shakey ground advising on AC especially on DIY.... Do the DC quad rules apply for the AC side.... Note do not use canare......? I found some 5 wire 1.5mm ..16awg cable Steel braid double clear sleeving. The 5th wire exactly as the earth. But use the 2 pair as the same method as the DC cable. These will be manufactured parallel not twist but I believe some medium heating below 100 Oc then mechanical twist and cool to help keep the spiral could work. Opposite paired live neutral basic geometry but would the 5th earth wire disrupt this? You don't have to answer all my ramblings but your basic thoughts would be great fully received on AC. This as a cheap one stop shop and keeping within regs I think... Doesn't have to be shielded braid, just this does for illustration purposes. Thanks as always for helping us all Kind regards Dave☺ .. Look at this on eBay http://www.ebay.co.uk/itm/201640606005 Starquad will do the same thing with AC power cable, significant decrease in inductance and built in shielding from DC on up. That cable you show will not get the starquad right, you need 4 wires which form a perfect square in cress section. This cable will not do that. John S. Middy 1 Link to comment
JohnSwenson Posted May 12, 2017 Author Share Posted May 12, 2017 21 hours ago, R1200CL said: How about the earth wire then? Cause a star quad with earth, will not be a star quad or ? (which I think was your point) Edit Just found this article that may be of interest for some of you. http://phmusic.co.uk/pharri5833/connections1.htm For AC power cable you need the hot and neutral in the starquad arrangement, the ground wire is then layed next to or wrapped around the starquad. VH Audio does this in their flavor 4 cable. You can get their starquad power cable for $10 a foot, plus you need a ground wire to wrap around it. Chris has not published a DIY recipe for the flavor 4, so you would have to "roll your own". John S. Middy 1 Link to comment
JohnSwenson Posted May 14, 2017 Author Share Posted May 14, 2017 1 hour ago, tboooe said: Hey guys...pls excuse the really nooby soldering question...when I try to apply solder onto my Canare cable and the Oyaide plug, the solder just forms into little balls. What do I need to do to make the solder "stick" to the wire and the connector? If you are using a flux cored solder there should be enough flux to tin the wire. The little balls mean you don't have enough heat. For me at least I've found the best way to do this is hold the wire in some sort of clamp, so you can hold solder in one hand and iron in the other. Melt a blob of solder on the end of the tip. Touch the tip with the melted solder to the end of the wire. Hold it there to heat the wire up. If you don't have melted solder on the tip of the iron this will take a LONG time, the melted solder transfers the heat to the wire. If you have the wire hot enough, touch the solder to the wire (NOT the iron!) and it will melt and flow into the strands by capillary action. It doesn't take very much solder to make this work. If this doesn't quickly flow into the strands, you don't have them hot enough. John S. Link to comment
Popular Post JohnSwenson Posted May 14, 2017 Author Popular Post Share Posted May 14, 2017 8 hours ago, R1200CL said: @JohnSwenson Are you involved in this design ? If yes, can you go to that thread and explain what the upgrade is ? Yes I worked on it, but I cannot discuss details of anything without explicit permission from my client (Jesus in this case) John S. R1200CL, MikeyFresh and Middy 3 Link to comment
Popular Post JohnSwenson Posted May 16, 2017 Author Popular Post Share Posted May 16, 2017 2 hours ago, Ralf11 said: I am also not clear on the benefit. You want low inductance to reduce voltage in DC power supply cable to a DAC because the voltage might cause noise in the DAC, i.e change the output. That would mean bits would need to be flipped, or jitter introduced. But how much voltage change on the DC power supply is needed to cause either? And how much Inductance results in what level of voltage? Also how strongly is the Inductance related to ripple in the DC power cord? Why not just reduce ripple? It's not ripple or noise from the regulator that is being filtered, it is changes in load current causing a voltage drop across the inductance of the cable. This is particularly important for digital devices due to large load changes that can be very rapidly changing, thus causing significant voltage change across the cable, even if the regulator is perfect. Many devices have power circuits that are not very good at rejecting rapidly changing supply voltages, so such changes developed across DC cables can easily wind up on parts inside the device such as clocks, analog circuits, DAC chips etc. Non of this is big enough to cause bit flips, that's not what any of this is about, it IS about letting those bits do their thing with the least amount of disturbance as possible. John S. Middy and Jud 2 Link to comment
JohnSwenson Posted May 30, 2017 Author Share Posted May 30, 2017 2 hours ago, Em2016 said: Hi @JohnSwenson Some very silly questions below but appreciate if you can help me to better understand this before I give it an attempt (I'm making some XLR and RCA cables using the Belden 1804A cable). Rather than PM you more questions, I thought it's best to post here to save you from getting the same questions from others. 1. With the external wire, are there any special requirements or things to note for the wire to use? A recommended wire gauge or particular conductor material? 2. This external wire doesn't itself need to be shielded, does it? 3. Is it best to solder this external wire to the shield at each end? 4. Do the potential static charges you mentioned affect audio? And how would you recommend to best add a resistance from the shield to ground? In particular with making up XLR and RCA cables with this method. Many thanks in advance #1: no special requirement, I wouldn't use 30AWG if you have 50 ft, 24AWG to 20AWG is probably fine. I have not done extensive testing on this, but 24-22AWG seems to work very well for normal length runs. I have been using some silicone rubber insulated 24AWG ultra flexible wire I got on Amazon. https://www.amazon.com/dp/B01LZ8UNCV/ref=biss_dp_t_asn #2: the shield connection wire does not itself need to be shielded. #3: Yes, solder the external wire to the shield at each end. Do not solder the shield (or external wire) to the "gnd" connection on RCA cables. Connect to pin 1 at both ends for XLR. SOME configurations may not need the pin 1 connection, but assume you need it to begin with. 4: you can ignore this, I shouldn't even have mentioned it. John S. Link to comment
JohnSwenson Posted May 30, 2017 Author Share Posted May 30, 2017 7 hours ago, Speedskater said: Belden 1804A cable would make a nice Star-Quad XLR balanced interconnect cable for harsh EMI/RFI environments (like near theater lighting systems). Not something most hi-fi systems need. But it's not a good choice for RCA unbalanced interconnects. Belden makes many good coax cables with heavy braided shields. With it's small conductors it's a bad choice for a DC supply cable. I'm not sure why starquad is bad for RCA, cables, IF you use the shielding topology I recommend it works spectacularly well. One pair of the quad is connected to the inner pin of the RCA plug and the other pair is connected to the outer conductor of the connector. The shield does not get connected in any way to either RCA connector, instead a separate external wire connects the two ends of the shield. This construction offers exceptionally good shielding from both the shield and the starquad geometry. This is much better than coax because with coax proper shielding does not happen. Without the connection from one end of the shield to the other shielding only happens at high frequencies. With the above shielding is highly effective from DC through high frequencies. The starquad works perfectly well with a "single ended" signal, as long as the shield is NOT connected to the plugs. The "hot" and its return form a perfectly symmetrical signal for the starquad. The problem happens when you try and use the starquad with the shield the way most people do it, this results in an asymmetrical arrange which unbalances the current in the starquad. With the shield connected the way I recommend this does not happen. The only issue is that the capacitance a higher than a coax. If you are driving the cable with a high impedance output and using a long cable (100ft or more) you definitely can have a problem from the higher capacitance, but most audio gear has low enough output impedance that for normal lengths used in home audio systems this is not a problem. John S. asdf1000 1 Link to comment
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