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HOME RECORDING TECHNIQUES

APRIL, 2000

BUILDING YOUR OWN CABLES

BY KEN LANYON

I know that every time I go into a music store to purchase an instrument or a mic cable, I am always amazed at how expensive they are.  I am sure I am not alone in this, and the question always comes up: "Why can't I just make my own cables? How hard is that?". Well, with a little soldering know how, the correct materials, and a little time, it's really quite easy and definitely less expensive.
First, I just want to quickly touch on the two main types of cables.   This would be balanced vs. unbalanced.  Balanced cables have 2 audio conduction wires and one ground wire. Examples of these would be all XLR and 1/4" TRS cables, which are often used for more professional equipment.  What happens here is that the audio information starts at the connector and is split down both the high and low wires 180 degrees out of phase from each other.  Then the audio on both wires is summed up again at your console or gear by a balancing circuit.  You may have heard that balanced cables give a reduced noise (hiss and hum) output and this is very true. Any stray noise like radio frequencies or the 60hz hum from your power cords being too close to your audio cables will jump onto both the high and low wires of your cable.  This noise however gets canceled out by the balancing circuit when the two signals are summed together and because the audio signal is out of phase with each other, they serve to reinforce the whole signal when flipped back into phase.  Of course, you always want to try and separate your audio cables away from the power cables or at least have them running at 90 degree angles to reduce the contact area of the cables. 
Unbalanced cables are usually used for more consumer equipment and exhibit increased noise because there is only one audio-conducting inner wire and one ground wire. This means that any stray noise jumping onto the audio wire is not canceled out and remains in the signal because there isn't another out-of-phase audio signal to merge it with and cancel it out. Again, no reason to have a balancing circuit with unbalanced cables, although any mixer taking XLR or TRS cables will.
O.K., the tools you are going to need for building these wires is as follows:
Soldering iron (25 watts is great)
Solder (60% tin/40% lead rosin core is what I use)
Damp sponge (not soaked - .just damp)
Wire strippers
Small screwdriver (various jewelers sizes)
Pliers
Digital Multimeter
The cable materials you will need will vary on what type of cable and connectors you are adding to the ends.  You don't have to stick with the same connector on each end either.  I have many cables with an XLR on one end and a 1/4" TRS on the other.  You can even make a balanced to unbalanced cable, and I will explain that as I get into the process of making the cable.  Basically, you will need a length you determine of 2 conductor shielded wire (or one conductor if you are making a full unbalanced cable), and the proper connectors for each end of your cable.   You can order these from a company like Newark or your local electronic store.
The Process
First start by plugging you soldering iron in at least 15 minutes before you start to work.  This will ensure that it is hot enough to warm up the contact point and melt the solder properly.  Of course, safety is an issue so I advise that the iron be used in a low traffic area away from crawling babies and that the power cord is not strung across a walkway.  Also make sure that the tip of the iron is not too wide.  You can buy these in different sizes and I suggest a small tip so that you can get into small places.
Next, cut a length of cable to the size you want (This is the great part about making your own cables! Custom lengths.).  Use your wire strippers to carefully cut through the outer rubber casing.  You can do this by closing down the wire cutters gently about a 1/2" from the end and rotating them in a circle around the cable.  Make sure to only go deep enough to get through the rubber because you may risk nicking or cutting through the metal shielding beneath.
Next, peel the rubber off and you will find a layer of paper. Cut away all of this paper, and underneath you will find the braided shielding.  Use your small jewelers screwdriver to carefully start at the top of the shielding and un-braid it all the way around. Bend it all down so it flows backwards towards the other end of the cable.  Again, you will find strands of paper that need to be cut away and bending back the shielding allows you to isolate and cut them away.
Now you will be looking at two insulated wires (usually black and white) and all of the shielding pulled back.  Go ahead and strip each wire about 1/4" from the tip.  Again, be careful not to nick the inside wire or conductivity will not be as efficient (or worse yet...you may cut right through it and have to start all over!).   At this point, I usually try to figure out the correct orientation of the wires on the connector so that the wires are not twisted around.  Quickly check to see where each wire will be placed (on an XLR connector, white/high goes to pin 2 and black/low to pin 3) and this will tell you on what side of the cable the shield must be placed.   Also check to make sure that the wires are not stripped too far back from the contact.  Having too much uncovered wire here may allow for two wires to touch at this point and short out.  Try to get the wire shielding just almost up to the contact and you may hove to trim down your wire to do this.  I would also suggest heating up the individual wires and spread a thin layer of solder across it to keep the individual strands of wire from fraying.
Knowing where your ground wire should be orientated, pull all of your shielding to that side of the cable and carefully twist it tightly starting from the bottom up.  You may have to clip off the tip of the shielding.  This will now become the ground wire attached to pin 1.  Spread a thin layer of solder on this also to keep the wires from fraying.  There should be a round plastic cover within your connector that slips over the connectors after they have been soldered as well as the metal casing that covers everything up.  Go ahead and put these onto the cable facing out.  This will save you much time and grief when you realize you have soldered all your connections but forgot to put these on the wire.  At this point, you may need a clamp of some kind to hold your cable down so that you can solder the connector on.   Now you are ready to solder.
XLR connectors will have the pin numbers written over the correct contact, but for 1/4" connectors, just remember that the longest is the ground, the middle is the ring, and the smallest is the tip.  Here I should mention two techniques about soldering.  First, keep your tip clean by melting a little solder on the tip and wiping it off onto the damp sponge.  This is called tinning and it helps to keep dirt from becoming part of your solder connection and increases heat conductivity from the iron to the contact/wire.  Secondly, before heating up a contact, place a little solder on the iron tip and then place the tip to the contact.  This again aids in heat transfer.
Soldering these connections can be a tough thing to do when you are balancing your iron, solder and both contacts.  For this reason, I like to put some solder on the contacts first so getting the right amount of solder doesn't take as long.   This is optional but you can do this by heating the back of the contact with the soldering iron and then adding the solder to the front of the contact.  It is important to heat up the metal contact first rather than just touching solder to the hot iron and letting it run off onto the contact.  This is because if you just melt the solder onto a cold contact, then you will get what is called a cold solder joint, which is really a weak connection that may break at any time.  Avoid this by always heating up the metal first. A few seconds is all it takes.
The drawing shows a freshly wired female XLR connector, just before reassembly & testing.

3_8b.gif (3908 bytes)

The drawing above is courtesy of Alexander Training Magizine and from Chapter 3 of the Book "How Live Sound Works" (Bolen/Dennis/Swiskowski). The entire text is online to Aledxander Magazine students.
Now take your wire, place it over the correct contact and heat the back of the contact (which will also heat the wire touching it).  1/4" contacts have eyelets that you need to thread the wire through, and in this case, I suggest placing the wire through and bending it closed with your pliers.  Then you can just heat up the connection and feed the solder right into the eyelet.  A few seconds after you see the solder on the contact begin to melt, add a little more solder to the connection until the wire is covered.  Be careful to not use too much because it can get messy and possibly join onto another contact, making them ultimately short out.  Take the iron off the back but remain holding the wire in place until the solder cools.  This should only take a few seconds.  Then the connection should be solid.  You can give it a slight tug to check.  Repeat this procedure to the other two contacts, using the correct wires.  Pull the round plastic covering over the connectors, and then the outer metal cover. 1/4" connectors will just screw on, and XLR connectors have a specific screw that needs to be tightened. 
The drawing shows a freshly wired 1/4" Guitar Plug, just before reassembly & testing.

3_8a.gif (2938 bytes)

The drawing above is courtesy of Alexander Training Magizine and from Chapter 3 of the Book "How Live Sound Works" (Bolen/Dennis/Swiskowski).

The entire text is online to Aledxander Magazine students.

Also, each of these connectors have specific parts that reduce the strain on the wire connections. On TRS connectors, you will find that the ground contact is bent inward towards the other two contacts, and this helps to keep them from getting bent.   On XLR connectors, a screw needs to be tightened securely to keep the cable from slipping or being pulled causing the wires to break from the contacts.  Take an extra look when you are finished and make sure these are protecting your cable properly.
Repeat the entire cable procedure to the other end, using the correct connector.  If you are making a balanced to unbalanced cable, you would solder the black/low wire to the same contact as the ground.  Examples of unbalanced connectors are 1/4" TS and RCA connectors.  If you were making a fully unbalanced cable like guitars use, you would only have one wire as a conductor and one ground wire.   The connectors would also only have 2 contacts.
Now that you have both ends finished, you must test them to see that all of the wires are connected properly and nothing shorts out.  Take your digital multimeter, and set it to the continuity setting (this is where it beeps when both probes are placed on the same metal circuit).  You can test these pins in any order but for point of clarification, I will start with the ground pin.  First, place one probe on the ground pin at one end of the cable, and place the other probe on the same pin on the other end.  If they beep, they are correctly wired. Now, make sure that the ground pin does not also beep to pin 2 or 3.  If so, something is incorrectly wired, and you must go back and look at the connection to see what needs re-soldering.  Then try pins 2 and 3 and check them with respect to the others. Pin 2 on one end should ONLY beep to pin 2 on the other, and the same for pin 3. In the case of a balanced to unbalanced cable, pins 1 and 3 on the balanced end should beep to the same ground contact on the unbalanced end.  If everything is wired correctly, then you have just finished your first homemade cable.  Congratulations!
Conclusion
Now that wasn't so hard was it?! Again, making your own cables is more reliable because you know how the connections were wired and if you took time to do it right, then they will last through some pretty rough wear and tear. It's also an advantage to make the cables to your custom length. The hardest part is really gathering up the supplies for the first time. Once you get through that, making more will be a breeze and you'll be happy to save yourself the money. Good luck and happy soldering.

Copyright 2000 by Ken Lanyon - ALL RIGHTS RESERVED

Published in REQ & Alexander Magazine With Author Permission

USE OF THIS ARTICLE SUBJECT TO USER AGREEMENT

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