Tiny shielded 2-conductor cables for tonearms?

The problem of the insulation layer stiffening the braided loom is solved by Cardas Clear 34AWG braided Litz cable which uses a microfibre wrapped insulation, making the cable smaller, lighter and much less stiff than traditional cables braided in the same way. It does need a special technique for soldering but fortunately there is an easy trick shown in this video:
Preparing Cardas 34 AWG Tonearm Wire
Cardas Clear Tonearm cable Product Information
 

cgallery

Member
2015-03-14 3:27 am
Thank you for this. I've previously looked at Cardas tonearm wire on eBay. I never noticed microfibre insulated product, only extruded plastics. And I would have sworn it was just two twisted pairs, twisted together. But now I do see on eBay braided wire that looks braided very similarly to the INTER-8 wire I posted above.

I don't think I actually need the microfibre insulation, the extruded would be fine.

So I'll add this to my list of things to try.
 
I don't think I actually need the microfibre insulation, the extruded would be fine.
I don't understand the purpose of your post: do you want a flexible tonearm cable or not? No extruded insulation is anywhere near as flexible as the fibre wrapped litz wire, and the Cardas 34AWG is vastly superior to anything else mentioned so far in this thread. The flexibility and thinness of the insulation allows a much closer braid, reducing the area between conductors for the permeation of magnetic fields.

I've been doing tonearm rewires for the past decade, both supplying the materials and for clients who supply their own materials, and I keep supplies of both of the Cardas braided cables. There is no comparison between the two, or between the Cardas 34AWG Clear tonearm cable and anything else I have come across for flexibility.
 
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In the 1970s some of the best tonearms had cotton covered Litz wire cables for flexibility. Cardas is the contemporary incarnation.

Just how much have you spent on your turntable, tonearm, cartridge, interconnects and preamp? The cable is a relatively minor cost for something that improves the performance of all of the above. The Cable Company, Parts Connection and plenty of other online stores sell the Cardas Clear 34AWG for $US50 per foot, which seems cheaper than eBay. the only downside is having to buy in units of one foot, making the minimum cost US$100. The cheapest on eBay seems to be eBay item number: 402606675484 and they sell it in multiples of 10cm.

About 10 years ago I had to buy AU$1000 worth of Cardas Clear 34AGW in order to get a wholesale quantity. I charge for it at AU$1 per centimetre (what it cost me then plus a modest margin), so around AU$40-50 per typical tonearm. Perhaps I am not as greedy as the typical eBay reseller, and I'll most likely die before I get my money back. For me it's about the result and the satisfaction of my clients.
 

cgallery

Member
2015-03-14 3:27 am
Actually looking at that microfibre cable again, it appears to be a simple twisted braid, so likely not suitable for my application.

It looks like a fine cable, but I've tried twisted wiring and I'm looking for something with better EMI/RFI rejection.

It is alright, our needs/applications are simply different.
 
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... I'm looking for something with better EMI/RFI rejection.
The Cardas cable has two twisted pairs which are then plied together for best crosstalk performance. Like all cable bundles the amount of EMI/RFI injected is a function of the physical space between the conductors, not the plait, braid or twist. Any winding of the conductors improves the balance of exposure between conductors to the external fields. Maybe braid gives a better balance but benefit is irrelevant without a balanced or differential input, where one of the wires is grounded at the preamplifier input terminal; the preamp will still amplify the EMI/RFI on the other leg!

If I can offer a thought exercise. EMI/RFI is in volts per length and/or magnetic field strength per area. Think of the bundle of wires as a volume intercepting the those fields, the larger the volume, the greater the energy intercepted. Note the electromagnetic fields do not exist inside the conductors so the relevant volume is the space between the conductors.

If there was any benefit in interference rejection of a braided cable, that benefit is overwhelmed by the increased space between the conductors due to the extruded insulation. And it will be much stiffer, both because of the insulation and because of the larger physical size.

It seems to me you have a preconceived idea of what you want and are not going to be swayed. Fair enough that's your choice, but not good approach to realising your stated goal.

For what it's worth, irrespective of construction, no amount of exposed unshielded cable cable feeding an unbalanced phono preamplifier is ideal. Without a differential amplifier input the physical wrapping or braid of the cable bundle is inconsequential to the amount of noise picked up; it is related to the physical space between the conductors alone.

Of course any braid or bundle is better than none because it keeps the conductor together, and if it constrains the movement of the conductors relative to each other then it will prevent microphonic pickup in the cable as well.

Any unshielded tonearm cable will degrade the noise floor of a cartridge / preamplifier, unless it is in a screened environment like a cage for example. I sometimes build cages around the tonearm base where the wires exit the tonearm to shield the exposed conductors.
 

cgallery

Member
2015-03-14 3:27 am
It seems to me you have a preconceived idea of what you want and are not going to be swayed. Fair enough that's your choice, but not good approach to realising your stated goal.

No, I'm simply rejecting the Cardas wiring for the time because I think, from experience with similar methods, that it will likely lack sufficient EMI/RFI rejection for my application.

I'm going to try the INTER-8 sort of braid. I know you say it won't help, but it isn't difficult to try it.

And I still seek, as I indicated in my first post, information on flexible sleeve with shielding, and also possibly sources for the Daburn cable in lengths less than 100ft.
 
Well hopefully the technical explanation of why the braided cable isn't going to do what you want will help others, if not you. If my posts are wordy, it is because I am trying to impart understanding that can be applied to other circumstances. The internet is so full of a perverted misinformation that it is hard to make an impression against all of the noise.

I thank you for the reference to Daburn and certainly their shielded cables look interesting. Unfortunately technical aspects that relate to its performance for tonearms are not all specified. It is likely to work well for MC cartridges, but might have too much capacitance for MM cartridges. The screen coverage is given as 90% coverage, which is only fair. Essentially for 50cm of cable, it will behave like 5cm is not screened, so good, but not perfect. Ideally the jacket would be made of conductive plastic to provide 100% screen, a technique used by professional cable manufacturer Canare in their GS instrument cables. Professional non-flexible hookup cables typically have a foil screen folded back on itself with a drain wire to give 100% cover with no leaks.

I would like to have considered something like Daburn 2712/4 when a few years ago a I rebuilt a Souther linear tracking arm, which would have made the task a lot easier. In the end I used flexible conductive plastic screening sleeve, donated from inside some Canare GS4 cable, to cover the Cardas Clear 34AWG cable wherever the extra stiffness wasn't an issue. Combined with foil screens along the raceway and grounding every bit of metal in the tonearm mechanism I was able to get the induced noise down to acceptable levels, though not eliminate it. The owner was ecstatic with the result, and still is many years later. The idea of planes of foil is that if grounded they "shade" the wiring from electric fields, though not entirely screening it. Mumetal and some steel alloys also work to deflect magnetic fields and need not even be grounded. Here's a simple yet effective accessory to reduce motor current induced hum in many Rega turntables: Hagerman Hum Bucker

You can see in the photo below the black tube behind the cartridge into which the wiring disappears; that is a piece of the Canare conductive plastic tube, which screens the cable up to the raceway. In the second picture you can see that there is a lot of unscreened cable along the raceway which needs to be super-flexible or it will induce skating forces, however by grounding all of the metal parts (which Souther had not done) and by installing grounded adhesive metal foil planes wherever I could out of sight, the noise pickup of the cabling was significantly reduced to almost inaudible, of course helped by the low output impedance of the Koetsu MC cartridge. Because of its proximity to the grounded metal bar, the section of cable to the right of the cable clip in the raceway did not benefit from a conductive plastic jacket, therefore I left it uncovered for looks.

P1000492.jpg


P1000490.jpg
 

cgallery

Member
2015-03-14 3:27 am
I don't know what the capacitance of the Daburn cable is. The Mogami is certainly on the high side compared to more conventional tonearm wiring. Still my total arm/interconnect/preamp capacitance is 120-pf (cabling measured with DE-5000), and I don't need any lower. The Daburn capacitance would likely be higher than the Mogami. Though, I don't know the actual figure.

I emailed Cardas to ask why they go through the bother of weaving some of their tonearm wires if twisting is actually superior. I'll let you know their response.
 
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I've been using Mogami ultra-flexible miniature cable to wire my tonearm: https://mogamicable.com/category/bulk/ultra_flex_mini/
Mechanical stiffness of a wire (rod/beam/whatever) goes as the fourth power of diameter, so separate single wires will always perform far better than a cable bundle from the point of view of forces/torques applied to the arm from the wires. A single 0.1mm copper wire twisted by 60 degrees over a 10cm length exerts a torque of 4.3e-6 Nm, A 0.3mm diam wire would give 81 times that torque, 3.5e-4 Nm. Those figures represent a force on the stylus (assuming 25cm arm) of 1.7mgf and 0.14gf respectively - the former is OK, the latter might represent 10% of the tracking force being used as a lateral force on the cantilever (not good). With 4 separate such wires the total forces go up by a factor of 4, if the 4 wires are rigidly bonded together the force might multiple by as much as 16 times... I don't think you can ignore these issues.

The calculations aren't as simple for composite cables made of copper strands and insulation you'd have to measure the torsional stiffness of the specific cable to figure out the effect it could have on tracking forces.

For a single strand wire of length L and diameter d the torsional stiffness is pi/32 d^4 G / L, where G is the shear modulus of the metal (4.4e10 for copper).

I think it is reasonable to assume about 10cm of the wire might be free to twist as the arm moves (less would be stiffer, note, so you want a good free length of the wire free to twist). I think something like < 0.2mm diameter separate wires is a good place to be mechanically.

[ BTW I don't see any mention of mechanical stiffness nor of cable capacitance in the Mogami docs, both of which can be important for tone arm wiring. ]
 

cgallery

Member
2015-03-14 3:27 am
I think I touched on this briefly in my original post, but to cover it in a little more detail...

The wire loop I'm using now is arranged so any torque imparted will be applied as anti-skating force. I've measured this by simply reversing the hanging weight arrangement, so instead of the hanging weights applying anti-skating, they're applying a skating force. So basically I adjust the weights until the arm maintains any position in which I place it. And I found that the Mogami wire applies the equiv. of 1.75g of of hanging weight at .5" from the pivot. So this is equiv. to 1.75 (.5) / 9.18, or .095g out at the stylus. In this instance, 9.18 is the effective length (inches) of my arm.

On my arm, this amount of anti-skating force is roughly equiv. to what is required for a cartridge tracking at perhaps .5g. For a cartridge tracking at 1.25g (for instance), I have to supplement the force imparted by the loop by hanging an additional 2.25g or so .5" from the pivot.

The Mogami wire's capacitance is rather high, around 60pf (IIRC) for the 17" or so that I'm using. This isn't a problem for me, as my total capacitance (arm, interconnect, phono preap) is still only around 120-pf. My tube phono, when I swap it in, adds another 50pf, so a total would be 170pf, still very reasonable. But there is certainly room for improvement here.

FWIW, I've over a dozen test albums and I'm very familiar with putting a cartridge/arm through its paces, this arm doesn't have any problems with tracking, With a cartridge like the XSV 3000, I can do in excess of 100um @ 315-Hz. I can sail through the entire Telarc mixed-tones test track. It passes all the Shure V15 V Obstacle Course tracks.

But I wouldn't mind if it would look a little more elegant. The commercial unipivot arms have much nicer looking wire loops.

I just don't want to give-up any performance.
 
I don't know what the capacitance of the Daburn cable is. The Mogami is certainly on the high side compared to more conventional tonearm wiring. Still my total arm/interconnect/preamp capacitance is 120-pf (cabling measured with DE-5000), and I don't need any lower. The Daburn capacitance would likely be higher than the Mogami. Though, I don't know the actual figure.

I emailed Cardas to ask why they go through the bother of weaving some of their tonearm wires if twisting is actually superior. I'll let you know their response.
The capacitance between two conductors is a function of the size of the conductors and thickness of the dielectric material between them. There's not a lot of difference in dielectric properties between plastics used for insulation, so for a given size conductor diameter and configuration the only significant variable is the distance between conductors, AKA the insulation thickness.

The thinner the insulation the higher the capacitance because the conductors are closer together. That's why film capacitors are made with the thinest plastic film that will withstand the rated voltage across them.

For the same size conductor the smallest overall cable size will have the highest capacitance, but whether that is significant or irrelevant depends on the connected cartridge's output impedance, namely low for MC (irrelevant in this context) and high for MM (possibly important in this context).

It will be interesting what Cardas have to say. Without commenting on value for money, their cables are generally well engineered and competently constructed. However their marketing, particularly for made up cables, has a bit too much voodoo thrown in for my liking. They only get to play with the same laws of physics as everyone else.

Edit: I just had a look at the three types of Cardas tonearm cable I have which are the same as the three on their website. The largest is 33AWG PVC insulated, slightly smaller is screened 33AWG PVC insulated (thinner insulation wall) and the smallest 34AWG with microfibre insulation. They all have exactly the same twist/braid design for the four conductors.
 

cgallery

Member
2015-03-14 3:27 am
The capacitance between two conductors is a function of the size of the conductors and thickness of the dielectric material between them. There's not a lot of difference in dielectric properties between plastics used for insulation, so for a given size conductor diameter and configuration the only significant variable is the distance between conductors, AKA the insulation thickness.

Yep, that is the "rub." Though I have tested some interconnects and have been surprised to find wildly different capacitance values for what appear to be very similar construction, from the outside at least. I can only assume that the proportion between the inside insulation, and the jacket, is different. I could cut the ends off and examine the construction better, but knowing isn't worth the cost. Maybe some day if I need to hardwire some RCA cables to something...
 
Yep, that is the "rub." Though I have tested some interconnects and have been surprised to find wildly different capacitance values for what appear to be very similar construction, from the outside at least. I can only assume that the proportion between the inside insulation, and the jacket, is different. I could cut the ends off and examine the construction better, but knowing isn't worth the cost. Maybe some day if I need to hardwire some RCA cables to something...
In a coaxial cable the capacitance is a function of the outside diameter of the inner conductor and the inside diameter of the outer conductor plus the dialectric constant of the insulator. A lot of coaxial cables use a foamed core to incorporate air in the dialectric and that reduces the capacitance compared to a solid-cored insulation. Those two factors explain the wide range of capacitance between similar looking coaxial interconnects, and the variation in such cables does not invalidate what I have already posted about headshell cabling which has different construction and certainly won't have foamed insulation. It's all simple (if poorly understood) basic physics.

Some years ago a hifi retailer who was at the forefront of the turntable revival asked me to test all of the interconnects they had in store for suitability for phono connection so they could make appropriate recommendations to customers. The retailer had several well known brand name cable manufacturers (to protect the guilty I won't name them) with interconnects up to several hundred dollars per pair. None tested particularly well and ALL regardless of brand or price significantly reduced the cartridge's performance, by introducing microphonic behaviour and/or degrading the noise floor. I've cut many of these cables open and I can confirm that given their construction they perform exactly as expected from our current understanding of physics.

As a consequence by arrangement with the retailer I tooled up to make professional grade cables that typically outperformed the brand name cables by >20db on signal degradation.
 

cgallery

Member
2015-03-14 3:27 am
The cables to which I refer are inexpensive mass-produced items with over-molded RCA plugs, with capacitance ranging from 120 to 500pf per meter.

I wasn't aware there were many expensive/boutique cables with over-molded plugs, all the ones I've seen could be easily examined by unscrewing the RCA plugs, no need to cut into them.