Nothing invokes more of a mixed response in Hi-Fi circles than the concept of 'audio-grade' Hi-Fi mains cables. The idea of spending up to £1000 for a mains cable for many, myself included, seems ludicrous. Audio grade mains cables are very much a Hi-Fi thing and not so much in the pro-audio world were the only time a slightly more expensive mains lead would be used is one that has screening to stop noise radiating out of the cable and inducing on other near-by more sensitive audio carrying cables. This does have some engineering sense behind it.
I am not saying audio grade mains cables do nothing, they do surprisingly make a difference but I think there is a need to be rational and balance the idea of spending say £1000 on a mains cable compared to the same amount on a set of speakers or amplifier were far more materials and or engineering has gone into designing plus producing the speakers and amplifier.
I have in the past dismantled a 300 USD audio mains lead at the plug ends and it was nothing special. It had 3 large mains conductors for L-N-E. This was covered in a thick foam dielectric, that being covered in a metal mesh screen and the whole covered with a PVC mesh so you could see the screen beneath. It was designed to look chunky and very pretty but only had some basic science behind it, namely the very low resistance conductors and a 'debatable' noise screen. It did not even use twisted pair construction.
When I say debatable noise screen, in most cases the screen is not needed and serves little purpose in the home environment. Screened mains cable is generally used when a long run is likely to be routed near other noise sensitive signal cables or near sources of RFI noise like machinery for example. Having a 1m screened mains cable when the cable behind the wall socket is regular twin and earth running in a large loop around the room and back to the fuse or breaker box is a bit pointless. Using twisted pairs will cancel RFI noise on the cable.
Cheap DIY Solution
My first experiment with 'audio-grade' mains cables was by chance hearing the difference one made in a good Hi-Fi system and then seeing its construction. I figured I could make something using the same construction method if not exactly with the same materials. These do make an improvement on my system which at the time of writing were tested on a Copland CDP, Yulong A100, Musical Fidelity M1 HPAP with Sennheiser HD 800, Stax Lambda Pro and Grado PS500's headphones plus amplifiers and speakers at other various times. Audio mains cables should really be last on your Hi-Fi to get list though, unless you are making your own which is easy and very cheap.
The second photo shows all the parts you will need to make your own.
- Brown and Blue 10A to 13A mains multi-strand copper.
- Green / Yellow 10 to 13A mains earth multi-strand.
- Tight PET flexible piping for the outer sheath. This can be bought off ebay.
- PVC insulation tape.
- Decent mains plug such as a MK.
- IEC plug.
- Copper or aluminium foil tape (optional). I usually skip this.
- Heat-shrink sleeving.
- Decide on the length of cable you want.
- Cut 2 lengths of brown and 2 lengths of blue multi core about 20% longer than you want the finished cable.
- Tightly twist 1 brown and 1 blue cable together along the full length making a twisted pair. This is time consuming.
- Repeat for for another brown and blue cable. This now starts to make your fingers sore.You will end up with 2 lengths of brown-blue twisted pairs.
- TIP : You can actually use a drill to speed this up if you have some help. Clamp the single brown and blue wire inside the drill chuck.
- TIP : One person holds the other loose end of the wires whilst you activate the drill on its slowest speed. This usually makes a more uniform twisted pair.
- Loosely wrap and spiral these 2 pairs around each other so you should now have 2 twisted pairs like in picture 3. Tape them together at intervals if you wish or wait until the next step.
- Wrap a length of green earth wire around both of these twisted pairs either using long spirals like I did or use a tighter spiral. Tape them all together at intervals along the length. Picture 4.
- OPTIONAL : You can now wrap this whole cable assembly in copper or aluminium tape for a screen. This however makes the cable quite stiff and any tight bends can rip the metal tape.
- OPTIONAL : You can buy bare braided screen and use this instead but it is expensive unless you can salvage some from old cable or TV antenna wire for example.
- OPTIONAL : If you use the metal tape route you must then spiral run a thin bare multi-stand wire along the length of the tape to make contact. This connects to earth at the plug end to form the screen.
- I tended not to bother with the screen in most of my builds since I prefer a cable that is very flexible and the dual twisted pair is enough to suppress noise. The screen serves little purpose in home use.
- You should now have a cable like picture 4 or 5. The optional build picture 5 does not show the earth screen drain wire at this stage.
- Slide the PET flexible sleeving over your new cable assembly. The PVC tape you used at intervals should stop it bunching as you do this.
- TIP : Use a lighter to melt the loose ends of the PET sleeving to stop it fraying.
- You should now have something that looks like picture 6.
- TIP : Do not try and cut the PET sleeving to length before you slide it over the cable. Slide it over and then once its almost covered with 1 end exposed about 1 inch cut the other end and trim to fit.
- Strip all the ends of the cables for fixing in the mains and IEC plug terminals.
- Obviously now twist the bare brown wires together and bare blue wires together at either end then tin the bare copper ends.
- Tin the stripped earth ends also.
- TIP : Before stripping and tinning the ends of the wire you will need to measure and trim them to suit the length needed in the plugs. Better to under estimate the waste and have to re-trim later.
- Cut 2 lengths of heat-shrink and slide these over the cable before fixing the plugs next. You can use black cloth tape later on instead which looks ok, or PVC tape if you are not too bothered.
- Fix the live, neutral and earth wires inside the IEC plug. You can either use the screw terminals provided or remove them and solder directly onto the terminal See picture 7.
- TIP : Soldering is a much better method. It is more secure and will never work loose over time.
- TIP : You may need to scrape or file away any zinc plating on the IEC solder points. The better quality IEC plugs are usually tin plated so do not require this.
- Finally fix the wires in at the mains plug end. Again you can actually solder the wires in the plug fixing holes so they never work loose and give a much better connection.
- TIP : Soldering the plug end needs a hot iron. I use a Weller and set it to 450 DegC for this. Clip and hold the brass plug prongs off the work surface using something like a helping hands tool.
- TIP : If soldering the mains plug end it takes quite a few seconds for the heat to transfer to the brass prong and start the solder flow. It gets very hot. See picture 8.
- Slide 1 of the heat-shrink pieces to cover the mains plug entry hole and the other to cover the IEC plug entry hole. Shrink them. Alternative wrap the ends in black tape.
- TIP : You will likely not be able to fit or use the IEC plug cable grommet due to the thickness of the cable but the heat-shrink completes the end and the cable grip holds it tight anyway.
- You should end up with a nice looking mains cable like the first picture.
Once you have made 1 or 2 it does get much easier to make them since you find little tricks and methods to speed the process up and avoid cutting ends to incorrect lengths.
These make a difference and only take a few hours to make. They also look very nice with the PET braid sleeving which is available in various styles and colours. I think many commercial audio mains leads sell on the look and wow factor but you can copy that look to some extent with some similar basic engineering ideas underneath in its construction. These simply rely on the fact it uses a dual twisted pair to cancel and suppress any common mode noise. The optional screen blocks any noise leaking out or into the cable. Use these with a decent mains filter to get the best results.