[DIY design] TNT Aircoil MKII interconnects

Tutorial for the building of TNT Aircoil MKII Interconnects

A detailed explanation on how to build them

Product: no compromise DIY interconnect cable
Manufacturing cost: between 100 and 250€
Reviewer: Piero Canova - TNT Italy
Published: March, 2022

Introduction

During recent weeks, after the publication of the article on the no-compromise Aircoil MkII interconnect cable, I have received several e-mails requesting clarification on how to build them and where to find the necessary components. I thought it would be useful to write a small tutorial to simplify the job for those who want to build them. Regarding the suppliers let me clarify that in some cases the availability of the parts isn't continuous and thus it might happen that the suggested supplier hasn't in stock the component you are looking for. With this in mind we can start the build.

PTFE tube: the best diameter is between 9 to 10mm; to avoid crushing it at the ends do not use scissors, but rather a sharp knife. My supplier is Freibo Tech Stores in Aliexpress. Remember to ask in the order to pack the tube in a loose circle avoiding creasing it otherwise, once creased, you won't straighten it again.

Mark on the tube the crossing points every 20mm. The first point is at 30mm from the end of the tube.

Hold the first silver conductor with a small piece of masking tape (the kind used in car body shops) placed 30mm from the end of the tube before the first crossing point. As you can see in the picture below, the conductor is held parallel to the PTFE tube. The 5N silver conductor can be found on Ebay or Aliexpress. In the latter, they have a wide choice of diameters down to 0,1mm. The best sources are GD-Parts Audio Store or Papri Audio Store.

Now we can start winding the silver wire around the PTFE tube with the wire crossing the points we previously marked on it. Essentially, we have a spiral that makes a complte turn around the tube each 20mm. Use a small piece of masking tape each 5-6 turns to keep the spiral in place. Take good note of the winding direction: in the picture, it is counterclockwise and you will need to remember this when you place the second wire.

Now we must insulate the first conductor with the PTFE tape. In order to ensure there is no short circuit, you must use three layers of tape. In DIY shops there are several widths: use the widest you can find since in this way you will cover the whole tube in fewer turns.

Mark again the crossing points, this time on the PTFE tape. Fasten the end of the second conductor again with a small piece of masking tape 30mm from the end, but on the opposite side of the first wire.

Now we can wind the second conductor as we did with the first, passing over the first at the crossing points. Since the first conductor was wound in an anti-clockwise direction, the second must be clockwise so they will overlap crossing on the marked points.

Now we can cover the second conductor with a second layer of PTFE tape. We can now insulate the conductors at the ends with some heat-shrink. Hold down the two heatshrink covered conductors with some masking tape. Here below you have a picture of how the cable should look at this stage.

Now we can insert the third conductor inside the tube.The length should be some 10cm longer than the PTFE tube on both ends. I have received several questions on the kind and quality of this wire. I am using some conductors coming from another disassembled cable; the quality is secondary and you can use both solid or multistranded conductors. Just don't use a conductor too thick to avoid problems of stiffness or during soldering. A color of insulation very different from the heat-shrink over other two conductors will help in minimizing mistakes. I have chosen black for live, red for return and green for the inner collector.

Now we can protect the cable with a braided cable sleeve. You can buy this on Ebay, Amazon, or in DIY shops. Choose the color you like in order to have a nice finish of the cable. Dark colors cover much better what's inside while pale ones tend to allow you to see the contents. This pale blue was recommended by my daughter who told me it is very trendy this year.

Finally, to cover the sleeve and keep the conductors tidy use a second piece of heatshrink. You can find several colors and I prefer to use red and blue for the two channels so I can identify them at first glance particularly when using XLR connectors which don't have any color markingon them. Depending on the type of cable you are building it will be convenient to add some sheath to hold together the three wires. Normally Cannon connectors prefer thin wires, whie RCA connectors where the connector is fixed through a small screw pushing on the cable, prefer larger diameters in the 7mm range.

Connectors: if you want to build a single-ended interconnect with RCA connectors then you will connect the wires as follows: black which we will use as positive on the center pinand red on the side pin. The green wire will be soldered together with the red, but just on one end of the cable. Mark clearly on the outer sleeve the end where you have soldered the green wire; this side must be always connected to the source component among the two you are going to connect. The cable we are building is then directional. On the opposite end trim the green cable to the length of the PTFE tube and block it with some blue-tack or alike so it won't rattle. Please remember before soldering that you must slide the body of the connector over the cable; I have forgotten to do this several times and these are moments in which your self-esteem isn't at its best. Which is the best connector for such a cable? Eichmann Silver Bullet Plug connectors are excellent but also WBT Nexgen 0110Cu give exceelent results and they are more affordable.

If instead you want to build a balanced interconnect then the connection scheme is the following: black on pin 2, red on pin 3. and green on pin 1 on both ends. Regarding the connectors, I prefer the Neutrik NC3MXX and FXX silver plated. They have reasonable cost and they perform very well, but if you prefer other brands they are fine too.

Conclusions

I hope the above clarifies most of the doubts, but if you still have something unclear please e-mail me. The final question from our readers was, "Can this cable be made with other types of conductor?". Of course, yes and perhaps you will find that some OFC or OCC copper better suits your tastes. Enjoy it.

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