Guide: How to Make a High-Quality Audio Interconnect for Your PC

hardnrg - 2007-05-21 18:20:04 in Modding
Category: Modding
Reviewed by: hardnrg   
Reviewed on: May 29, 2007
hardnrg
Price: £15+

Introduction:


Ok, so you've got a high-quality soundcard, and a decent amplifier/receiver and some nice speakers, but what do you use to connect your pc to your amp?  Most people use the cheapest, piece of crap cable that they picked up for pocket change because it does the job.  But what if you want something better and don't want to pay a stupid amount of money on an audio interconnect?

The answer? Make your own!

Here's what I ended up making for my main computer to my amplifier, a 5 metre 3.5mm stereo jack plug to twin phono/RCA cable:



It uses high quality cable and connectors, and looks and performs like the type of interconnects that cost a lot more.  So, what determines the cost of this custom interconnect?

What You'll Need:


There isn't really much point totally cheaping out on the cable and connectors here, else you may as well stick with that piece of crap cable you're using at the moment.

Materials

Here is a list of the materials and components used for this cable:


I already had the silver solder, clear tape, and the heatshrink, so I only paid for the braided cable sleeving, cable and connectors.  The cable and phono connectors are usually more expensive, but I got these from work for cheap.  A total cost of £15.11 for the materials I needed.


Here are the 3.5mm and phono connectors I will be using:


You could use individually or overall screened cable.  Theoretically, individually screened minimises the likelihood of cross-talk.  I went for this overall screened cable because the signal cable uses a mixture of high purity oxygen-free copper (OFC) and silver-plated OFC, and the screen itself is OFC which is also good because the screen carries the signal for single-ended systems (a single-ended audio system uses a signal and a ground, as opposed to a balanced signal where the signal is carried over two complementary magnitude signals with a shield that doesn't carry the signal).  Anyway, enough of the techno-babble, this is what you're aiming to get, a single round cable with two cores with either individual shields or a common shield:


For adding protection and a touch of refined style, I decided to use black braided nylon cable sleeving.  This is not really necessary, but I think it just looks cool.  The same type of sleeving is used on Monster AV cables, PSUs, etc.  I chose 6mm braiding as the cable has an outer diameter of 6.35mm (1/4"). Heatshrink and double-sided tape will be needed for the cable split.


Tools

Here is a list of the tools I used, not all are required, but you'll probably find them useful for making the interconnect:


Here's my trusty soldering iron, you could probably use a 25W iron or something, but I prefer putting my 50W variable iron near the hottest setting so I can apply a lot of heat quickly to the terminals of the connector to avoid melting the plastic component parts of the connector.


Over here in the UK we must have the most heavy duty mains plugs in the world. It takes 13 amps at 240 volts, holds fuses (3, 5 or 13 amps) and can stand a lot of physical abuse. I've not seen a more heavy duty standard mains connector in the USA, Europe or Asia. I took a picture of it to show how awesome it is! If you stand on one of these, the pins don't bend and you hurt your foot!


The flux applicating pen is not required, especially if you have multi-core solder, but most people like to use flux for making the best connection.



If your chosen cable contains silver, then silver solder is required, otherwise it's optional.


The crocodile clip stands I find so useful for making cables that I always use them.  I don't have to use them, but it would be a lot more annoying and time-consuming without them.


 

Preparing The Cable:


It takes a while making a custom cable 5 metres long, and it would take a while for any length really, so it might be a good idea to get your choice of tasty beverage and put on some music to keep you refreshed and entertained!

First of all you'll want to measure out the cable and larger sized cable sleeving.  I measured out the cable to be 5 metres and the cable sleeving the same length.  It's pretty much guaranteed that when you put the sleeving on the cable, it will end up a bit shorter, this is what I intended as the larger sleeving starts at one end, but only goes as far as the split for each channel (left and right).  A tape measure is handy here.


Now, the thing about braided cable sleeving is that once you cut it, the loose ends quickly become frayed.


This is avoided by melting the freshly cut end by briskly waving a lighter's flame back and forth across the end. You don't want to set the braid on fire, just heat it enough to melt it. If it catches alight, you can just blow it out.
 

And then you should end up with it looking like this.  When you actually do this, you can hold the sleeving in your other hand, I just had to use a short piece of braid in the crocodile clip stand to be able to take a photo!
 

Now the braided sleeving can be pushed over the cable without it becoming frayed.

The method of getting the sleeving over the cable is kinda like a caterpillar walking. First you hold the sleeving at the "head" and push the "tail" up so that the braid becomes compressed.


Then you hold at the "tail" end and let go of the head and the braiding will spring forward by itself.


 
 

Making The Interconnect - 3.5mm Jack Plug End:


You'll have to smooth the sleeving over the cable from tail to head to get it to go over properly all the way. After a while you'll get the sleeving over the cable. Leave a bit hanging over the tail end and pinch it down to put the connector barrel over the sleeving and cable, push the connector down along the cable and then work the sleeving down to expose then end of the cable.



Cut the sheath of the cable, taking care not to cut the shield. I find it easiest to use a sharp knife and cut around the sheath and bend the cable to split it at the cut. So I don't actually cut all the way down to the shield.


Make sure you remember to place the insulating tubing over the cable if you are using a metal barreled connector


Size up the signal cores against the connector and trim them down to line up with the terminals. I used blue for left and red for right. On a 3.5mm connector, the centre terminal corresponds to the tip of the jack plug, which is the left channel. The middle terminal corresponds to the ring or middle section of the jack plug, which is the right channel. The shield connects to the larger outer terminal.


Strip the signal core cables down, apply flux and tin them with a small amount of solder. Apply flux to and tin the shield wires too.


Line up the cable to the terminal and hold in place. This is something I can rarely do easily without the use of the crocodile clip stands. Then dab on some flux and apply heat to both the terminal and the core cable, and let the solder flow onto both. You should end up with something like this.


Do the same for the left channel (blue in this case) to the centre terminal.  As you can see, I twisted the shield into two parts, this makes it easier to solder than one big twisted shield, trim it down to size, apply some flux to it and the shield terminal, and solder one near the edge of the inner side and one to the opposite edge


Inspect the solder joints to make sure they are solid and not cold-soldered. Use some pliers to clamp the cable down firmly, and then slide the insulating tubing up over the connector assembly.


Push the braided sleeving back up. You could wrap a couple tight turns of electrical tape around the sleeving to secure it in place at this point. I chose not to because the cable, sleeving and connector make a perfect snug fit (no coincidence since I chose them to allow this).


Time to take a quick break, get a refill and admire the first half of the job!


 
 

Making The Interconnect - The Phono (RCA) End:


This end is a bit more involved as you need to split the cable to the left and right channels, prepare the cable and sort out the Y-split.  Don't worry though, it's all straightforward enough.

Cut the sheathing off, but this time a longer amount as you'll be splitting the cable. Some people take the sheath off in sections, others cut the sheath lengthwise and peel it like a banana. Whichever way you do it, try not to break the shield as it carries the signal aswell. Unravel the shield from any internal insulation.


I removed the papery-cloth insulation, but kept the string.  I separated the shield into two equal parts and twisted them.  So I ended up with the two signal core cables, two twisted shields, and two string bundles.
 

You can braid three or more cables together for strength, neatness, and maintaining the shielding.  If you don't know how to braid, either look it up or ask your girlfriend/sister/mother/friend.



I used some masking tape to hold the new braided sections together while sliding over a piece of heatshrink. This length of heatshrink needs to be long enough to extend up into the phono connector, but not all the way up.



Before you commit to the heatshrink, it would be a good idea to test the cable for continuity. Use a Digital MultiMeter (DMM) either set to continuity beeper, or the lowest resistance setting and check the end-to-end connection from the jack plug to the bare cables at the phono end.  I measured 0.7 ohms on each signal core, and I don't remember what the shield was but it was the same or lower. Matching the resistance means you have equal signal transmission on both channels.


I used a lighter to shrink these small sections of heatshrink which is ok as they will not be seen. Using a lighter can easily end up with a sooty/charred appearance to the heatshrink. You could also use a hairdryer or heatgun. After shrinking the heatshrink, I cut some short sections of the smaller size braided sleeving and slipped that up over the heatshrinked section. I put some doubled sided tape around the heatshrink nearest the Y-split for the braiding to hold on to.


I worked the larger braiding back down over the cable, and when it was in the right position, moved it back a bit to put some double-sided tape around the cable sheathing so the larger braiding could hold on to the cable near the Y-split.


I cut some of the larger sized heatshrink and slipped it over all the sleeving.


Then I made two short sections of the medium sized heatshrink and slid that over each split piece, heatshrunk those, then slid over the large heatshrink back up over the entire Y-split and heatshrunk that.  This time I used a hairdryer as these lengths of heatshrink are visible on the final cable assembly, so a clean appearance is necessary.


Remove the masking tape and measure up the cable to the phono connector, you want to end up with the sleeving inside the connector and will probably end up with only a short piece of signal cable and shield protuding. Remember to place the connector barrel over the cable before soldering! Flux and tin the cables in the same way as before.  I used a scrap piece of cardboard to avoid damage to the sleeving while being held in the crocodile clips.


And then the soldering process is pretty much the same, the signal cable goes to the centre terminal, and the shield goes to the larger outer terminal. I had to apply quite a lot of heat to the shield terminal on this connector. If you have a variable heat iron, turn it up to avoid melting the plastic insulating parts of the connector.


Finish up soldering, clamp it, screw up the barrel, do the other one in the same way.  Once you're done it would be a good idea to re-test the continuity from end to end using the connector tips as the measurement points.

 
 

Final Product Photos:


Here are some fancy-pants pictures of my finished cable.





Conclusion:


Replacing the rubbish old cable with the new custom one and listening to some music surprised me a bit.  The music sounded much more animated and was coming from further out each side than before.  Also there was more detail in the sound with vocals and instruments being more defined, clear and precise.  All the differences were subtle, but certainly there, a relief that all that hard work had not been in vain!

If you love music and listen to digital formats through your computer and have an analogue amplifier I recommend making your own custom cable.  Obviously, if you have some rubbish speakers then you probably wouldn't hear the difference between your custom interconnect and a wet piece of string.  But, if the interconnect is the weakest link in your computer audio set-up, replacing it with a high quality cable is well worth the effort.