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TNT Shoestrings

DIY interconnects

[Italian version]

Product: TNT Shoestring interconnects
Manufacturer: not for sale, TNT-Audio DIY design
Author: Nick Whetstone - TNT UK
Published: September, 2005

I've been making interconnects since I first got interested in the DIY side of hi-fi. I knew that cables could make a difference to the sound but I certainly didn't believe that performance was necessarily related to cost. DIY offered me the only viable solution to trying as many different cables as I needed in order to find the best one for my system. After many attempts, I found an interconnect that satisfied me. And when I made a pair for a friend's high-end system that improved it so much, I knew that I had hit on a good "recipe".

So why are they called TNT Shoestrings? Well they had to have a name, if only for the purpose of writing this article. I chose the "Shoestring" name for two reasons. The first is that they use shoelaces (or boot laces) in their construction. The second is that they can really be made on a shoestring budget (unless you go crazy on the plugs of course).

Not only are they relatively inexpensive to construct, they are also fairly easy to put together with a bit of care. So let's see how it is done, starting with a list of what you will need to build a pair!

[Shoestring interconnects - materials needed]

  • Some CAT5 solid core wire. (you could also use 0.6 mm solid core silver-plated wire). When calculating how much wire you will need for an interconnect,remember that the wires are twisted around the centre core and are consequently about one third longer than the length of the finished interconnect!
  • A set of four phono plugs, two black and two red. I have found that you can get very good phono plugs for not much money but you have to find them first, sadly by trial and error! Some plugs are too tight when connected to a phono socket and fitting and removing them often will weaken the socket! The fit should be tight but allowing the plug to be removed smoothly. The plugs used for these interconnected must cater for a minimum of 6 mm diameter cable.

  • [Cross section of coaxial cable core]
  • Coaxial cable (as used for ordinary television/satellite arials). It doesn't have to be new so if you can find some old stuff for free, so much the better! This type of coaxial cable has the channels running along the length of its core, ie it is what they call air-spaced. The inner conductor is easy to pull out leaving a flexible core. Please note that not all cables of this type have the removable core, not all of them have the air-spaced core. If you cannot find this type of cable, you could substitute some small-bore plastic tubing of the sort used to pump air into an aquarium. Exact diameter isn't too important so long as your finished interconnect will fit in your chosen plug.
  • Solder.
  • Insulating tape. Sellotape can be used instead.
  • A pair of shoelaces (not shown in this picture). Used to cover the interconnects.

[Shoestring interconnects - tools required for construction] And here are the tools that you will need.

  • Soldering iron. Nothing too special required for this job but it always pays to own a good 'iron'.
  • Mini vice. This isn't essential but makes the job a little easier. It can be used to hold one end of the interconnect while you are constructing it, and also to hold the phono plugs while you solder the wires to them.
  • Needle nose pliers. Ideal for holding the wires while you thread them through the inner core. Also handy when soldering the wires to the plugs.
  • Wire cutters. Used for both cutting the wires and stripping them. You may use a dedicated wire-stripper if you prefer.
  • Sharp scissors to cut the shoelaces. Blunt ones will fray the shoelaces.
  • Sharp knife. For cutting the coaxial sheath and making the cuts in the inner core.
  • Multi meter. For checking the connections after you have soldered on the plugs.

[Shoestring interconnects - removing coaxial sheath]

The construction

Start by taking a piece of the coaxial cable the same length as your intended interconnect. The first job is to remove the outer sheath. Take a sharp knife and cut along the cable as shown in the picture, about 150 mm should be enough. Be careful here, it is very easy for the knife to slip if the cable rolls over as it can easily do!

[Shoestring interconnects - removing coaxial sheath]

Carefully pull the inner core of the coaxial cable out through the slit that you have made in the sheath. Once you start pulling the core away from the sheath, the latter should tear right along its length, allowing you to completely remove the inner core.

[Shoestring interconnects - preparing the inner core]

Next remove the copper braiding from the inner core by sliding it off. Then pull out the wire from the centre of the core. This isn't shown in the pictures because I had previously removed it to use on another project.

Now make a small V-shaped cut in the plastic inner core about 100 mm from one end. Be careful here, you don't want to make the cut too big and unnecessarily weaken the inner core too much. The cut should be just deep enough to allow you to thread the CAT5 wire into one of the channels that run along the length of the core. Do the same on the opposite side of the inner core. If you stagger the cuts by a few millimeters, it will keep the inner core stronger. Now repeat this step at the other end of the inner core.

[Shoestring interconnects - threading the conductors]

Now take a length of the CAT5 twisted pair and untwist it so that you have two single wires. Straighten them out as much as you can between your fingers. Remember that you need lengths of wire about one third longer than your finished interconnect! Thread a piece of the CAT5 through one of the V-shaped cuts, and into a channel. Carefully push it along the channel until it emerges at the end of the inner core. Leave about 25 mm protruding.

Now do the same with the other piece of CAT5 in the cut on the opposite side of the inner core. I remind you again, care is needed not to break the inner core where the cuts are so do this very gently.

[Shoestring interconnects - twisting the conductors around the iinner core]

Now the best way to do the next stage is to secure the end of the inner core that contains the two wires in a vice or something similar. Or get a friend to hold the end for you. If you have neither vice, nor a willing helper, sit on a chair and hold the end of the inner core between your feet.

Where the two wires emerge from the inner core, cross them over each other and then about 25 mm further along the inner core, cross them over each other again but on the opposite side of the core as shown in the picture to the right.

Repeat this process until you reach the cuts in the inner core at the other end.

Remove the inner core from the vice and very carefully pull the wires tight so there is little or no slack in them. They want to be fairly tightly wound around the inner core.

Now feed each wire through each of the cuts in the inner core, pull them tight, and trim them off, leaving about 25 mm protruding from the inner core.

[Shoestring interconnects - twisting the conductors around the inner core]

Repeat the whole process for the second interconnect.

You should now have something resembling the picture on the right!

Now take a pair of shoelaces long enough to cover the interconnects. They need to be wide enough so that the inner core assembly can be threaded through them. It should be quite easy to find the right sort of laces and if you are lucky, you may get a choice of colour too!

Cut off the hard tips of the laces so that you are left with a 'tube'.

[Shoestring interconnects - folding the conductors to help them pass through the shoelace]

In order to get the interconnects to pass smoothly through the shoelace without snagging, fold the ends of the CAT5 wires over and temporarily insert them into the spare channels of the inner core as shown here.

Now carefully thread the inner core assembly through the shoelace. I find it easiest to push the lace onto the core and then pull it along, rather than try and pull it on!

[Shoestring interconnects - inserted into the shoelace]
Leave about 10 mm of exposed core at each end of the shoelace. It will make it easier to fit the phono plugs if you secure the shoelaces to the plastic inner core with some insulating tape (Sellotape will do just as well here).

Here you can see the interconnect covered by the shoelace. Leave a little more exposed inner core than shown in this picture so that the tape has something to adhere to.

You are now ready to solder on the phono plugs of your choice.

[Shoestring interconnects - the finshed item]

And here is the finished item. Quite smart and a change from the more usual heat shrink tubing. The shoelace covering also makes these interconnects more flexible and there is a good argument to say that not adding more plast../jpeg/rubber insulation is beneficial too!

And of course we can have hours of fun discussing which is the best sounding shoelace too! But seriously, I think that you will agree, these are very good sounding interconnects. They are even-handed, not favouring one part of the frequency range. Detail is excellent and they have the ability to open up the sound stage.

The silver-plated wire versions sound slightly more bright than the CAT5 version.

© Copyright 2005 Nick Whetstone - www.tnt-audio.com

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