Making Your Own Interconnects
By Gary Markowitz
|After doing some interconnect shopping a few years ago, I came to the realization that to my ears high end interconnects and speaker cables were either way overpriced, or they screwed up the sound. No, I don't believe that all cables and interconnects sound the same. In some instances, only cables with certain characteristics will work well with specific components. Cables and interconnects do sound different, but to me, any effects were subtle, and a lot of the cables I've tried did alter the sound for the worse.|
|Give me $500 to spend on audio whichever way I want, and I'd much rather buy more vinyl than one pair of interconnects. So I did a bit of research into what should make a cable or interconnect good. Here's what I found.|
|The ideal cable should pass an analog signal with no loss whatsoever, flat from DC to light. But no cable yet devised can do this. Interconnects in the real world act as filter networks, who's behavior is governed by it RLC (resistance, inductance, capacitance) parameters. In other words, a cable acts like a network comprised of a resistor, a capacitor, and an inductor (aka choke), very similar to the crossover network in a speaker.|
|The idea is to keep the filter network's operation as far above the audible range as possible. To properly figure out the exact characteristics of the filter created by the wire, you need to know the output impedance of the source component, and in input impedance of the load component, as well as the RLC measurements of the wire itself. Rather than get into the complexities of the math, suffice it to say that in general, you will want to keep the capacitance and inductance as low as possible, unless of course the manufacturer of the component recommends specific criteria, as does Naim for example. They recommend high inductance speaker cables for the proper operation of their amplifiers.|
|My design criteria consisted of the following list, based both on my research and past listening experiences:|
- Teflon insulation. Since the wire acts in part as a capacitor, Teflon is recognized as having among the best dielectric properties.
- High purity OFC copper
- Solid core conductors
- Readily available and relatively inexpensive.
- 24 ga. signal conductors. I wanted to minimize any possible skin effect on the cable. This is a fairly controversial topic, and I'm not sure myself if skin effect is audible or not for audio applications, but why take a chance?
- High quality Teflon insulated RCA jacks.
About the wire itself
|After looking around for a wire to meet the above criteria, I found Category 5 Plenum Networking Cable. This is the wire computer networks use for 10 megabit or faster communication. Cat 5 has a bandwidth of approximately 350 mhz, with enhanced Cat V good to 1 GHz. Bandwidth would be no problem. The spec for Cat V calls for 4 9's or better (99.99+ pure) OFC (oxygen free copper) wire. This is for the most part the same stuff that most interconnects are made of. The plenum variety is Teflon insulted, making for very good dielectric properties, and having the added benefit that a soldering iron won't melt or burn the insulation. In it's most common form, it comes as 24 ga. solid core wire. It is readily available from almost any networking catalog, electronics catalog, or local electronics shop for well under $1 US per foot. So for the wire, all design criteria are met.|
|This interconnect is very unforgiving. It will not tame brightness, increase bass, bring out or mask detail, sweeten or romanticize the sound. Therefore, it might not be the right cable for all systems. What it does is give you whatever your components are capable of producing, while not drawing attention to itself or otherwise alter the balance of sound in your system. I'm not saying it's perfectly transparent, but it comes as close as anything I've yet had in my system, including some interconnects that cost well over $500 per meter.|
|Parts you'll need (1 meter pair unless otherwise noted):|
- Category 5 solid core Plenum (Teflon insulated) networking cable - 4 feet will make 2 pairs of 3.5 foot interconnects
- Polyoelefin heats shrink tubing - two four-foot pieces per pair
- 2 rolls Teflon plumber's tape - available at any hardware store
- Aluminum foil - 1 approx. 2 ft by 1 ft sheet
- 4 good quality RCA connectors, preferably color coded for each channel
- 22 Ga. or smaller bare tinned solid core wire
- Solder - preferably silver bearing.
|Cat V comes as 4 twisted pairs in the sheath. So to start with, cut the cable to the length you want plus about half a foot for a safety margin. Strip off the outer sheath, and separate the bundle of wires into the 4 twisted pairs. Each pair should have a solid color wire, most common colors being blue, green, orange, and brown. The other wire in each pair will be either white, or white with stripes the same color as the solid colored conductor.|
|Choose your two favorite colored pairs, which will become your left and right channel interconnects.|
|This part is optional. If you wish, you can twist the pairs tigher by connecting one end of the twisted pair to a piece of wood, and the other end to the drill chuck. Run the drill very slowly while keeping the end attached to the wood stationary. Twist the wire until you have between 6 to 10 twists per inch. Theoretically, this should increase noise rejection, but it has the added benefit of making the final wire more flexible.|
|Once you have both pairs twisted to your satisfaction, take your plumbers Teflon tape and proceed to wrap each pair by spiraling the Teflon tape around the wire. Wrap at least two layers, as this will provide additional insulation between the signal pairs and the foil shielding and will slightly reduce the wire's overall capacitance..|
|Take the 22 Ga. tinned bare copper wire and loosely spiral it around the Teflon coated twisted pair. This wire will contact the foil shield and provide an easy method to connect the foil shield to ground. |
|Next, cut the tin foil sheet into several 1/2" strips. Cover the prepared twisted pair and drain wire with the foil by spiraling it around the wires. Make sure that there are no gaps. You shouln't be able to see any white Teflon tape, only foil. You will need several strips to cover the wire fully, just overlap the new one over the old one a little bit and you'll be find. Same advice if you accidentally break the foil.|
|Once you have everything properly shielded, wrap the bundle again with Teflon plumber's tape. Pull the tape tight , compressing the foil tightly against the wire bundle underneath. This will not only reduce the diameter of the wire, but also serve to make better contact between the foil shield and the drain wire. Again use at least two layers here.|
|Now use polyolefin heat shrink tubing to cover the entire assembly. 3/16 diameter should do fine, although you might want to try 1/4", as it's easier to thread the interconnect. Either way, it should shrink down to a comfortably tight fit around your wire assembly. Since I don't have a heat gun, I use an ordinary clothes iron set to the second setting and an ironing board|
|Now, cut the wire to it's final length, plus about an inch on each end. This will allow a little extra room to strip and solder the assembly to the RCA jacks..|
|Strip about 3/4 of an inch of the heat shrink tubing from the assembly on each end. You'll need to be careful not to cut into any of the conductors. Now strip what's remaining of the Teflon tape and foil off the assembly at each end so it's flush with the heat shrink tubing. On each end you should see only one solid colored conductor, one either solid white or white with colored stripes, and one bare tinned wire.|
|Take the Teflon plumbers tape and wrap about an inch worth of the tape around one end of each wire, being careful to cover only the heat shrink tubing and not the wire ends you've just prepared. This will mark the end of the cable where the shield is grounded.|
|Strip 1/2 in of the insulation off of each of the individual conductors on both ends of both cables. Make sure you can still identify which is the solid color and which isn't. Cut the bare tinned wire flush with the heat shrink on the end of each cable not marked with the plumbers tape. |
|Now you're ready to solder. Solder the solid colored Cat V wire to the center conductor of each RCA jack. Make sure you slide any of the necessary hardware onto the cable assembly before soldering (don't laugh, I've done this on more than one occasion). Then solder the white or striped conductor, along with the bare tinned wire on the Teflon tape marked end of the cable assembly, to the RCA jack ground.|
|If your RCA jacks have a cable clamp, carefully tighten the cable clamp around the cable assembly. Make sure it's snug, as this will provide strain relief to your soldered connections. But don't tighten too much as you don't want to cut into any of the wire insulation. I used the cardas jacks, which don't have strain relief. What I did was to fill the back end of the jack with silicon caulk, while being careful to keep the cable assembly centered. This provides adequate strain relief, but requires more caution in handling than the jacks that use either plastic or metal clamp strain relief.|
|The cable should require no more than a couple of hours break-in. The sound of mine settled in nicely after about 3 album side. The side end of the wire that does not have the Teflon tape marker should be connected to the source component.|
|Listen away, and let me know what you think.|