Audio Cables; General Information

12/97 updated 10/03 - Jens Moller http://www.colomar.com/Shavano/audio_cables.html

What is the best cable to buy? This is a loaded question that cannot be answered by simply mentioning a brand. Like everything else a musician or singer faces, the answer all depends on what you are doing.

Before we get into any discussions about what makes cables good and what makes them bad, let me give you a simple fact of life: For every cable you have that is not pre-wired inside of a cabinet, it will eventually fail. It makes no difference who made it, or how well they put it together - eventually, you, or someone who is working around it, will do something to cause it to fail. The problem is that you cannot plan for every possible thing that might happen to you and build a cable that will not fail somewhere along the line as a result. You can certainly buy or make cables that will hold up better than others, and there are cables out there that are such garbage to begin with that using them is asking for trouble.

Let me also mention that there are differing opinions about some of the High-End Audiophile cables. If you feel that there is a difference in the sound based on your experiences with this type of cable, and want to use it - please feel free to do so. I have been involved in blind listening tests, and I couldn't tell the difference between the ultra high end cables and the middle of the road good quality cables. I personally don't believe the hype that is associated with them. This article will deal with good quality cables, but at no time will I reccomend these high end cables - If you want to use them, go ahead, there is nothing wrong with them - I just don't feel you will gain much for the extra cost involved.

Sudden Cable Death Syndrome (SCDS)

The following are common SCDS instances that I have experienced:

• Stepping on one of the connector covers.
• Tripping over wires (tearing wires out of connectors).
• Corroded wire junctions (usually where the wire and connector join).
• Running the wheels of a heavy case over wires lying on the floor.
• Putting something heavy on wires that are laying on the floor, then moving what ever the other end of the cable is plugged into.
• Dropping a heavy case on wires.
• Failure of connector.
• Eventual internal stretching of cable, breaking one or more wires inside the cable.

What it the lesson here? Its that bad things typically happen to cables that are lying on the floor, unattended. You can avoid people tripping over them if you use Duct-Tape (or other fabric based tape at least 2 inches wide) to hold things down to where you want them to be. There is nothing you can do to prevent people from stepping on the cables or the connectors (you'll even do it yourself a few times) - but you can use connectors that have metal covers (not plastic) where the wire junctions are. You can also route bundles of wires behind areas where there is high traffic - reduce the opportunity for the damage to occur in the first place. Treat these things with respect, but realize that cables cannot be protected from everything.

Also, never forget that the jacks that your cables plug into will also eventually fail too - You might as well become more familiar with where the problems are and how to protect yourself when SCDS comes knocking on your cable case.

Components and failure points of an audio cable

A Cable may, or may not have the same types of connectors on both ends. For audio work, these are often 1/4 inch Phone Jacks, XLR connectors and RCA Phono-Jacks. Don't let the names fool you - These were named a long time ago for the function they served then, and the name remains even if you are using it for something different. Some speaker cabinets use unique connectors that limit the type of cable that can be plugged into them - this is good in the sense that you probably won't hook the wrong things up to the wrong cables, but since connector failure is very common, you will need to find sources of these connectors for repair purposes and making spare cables. I often need cables with different connectors on each end to allow me to use devices that happen to have different connectors on them. This can be a royal pain to deal with, but over time, you will probably accumulate a few adapter type cables to allow you to do this.

The connectors and the wire junction points at the connectors is probably responsible for 90% of all SCDS failures. Most frequently, these are where the flex points are and the wire breaks right where it is attached to the connector. From the outside, everything looks just fine, once the connector cover is removed, then you find one or more broken wires. As long as the connector is in good shape, and the connector allows for it, this is repairable. Connectors that are molded together are not repairable - you have to cut the end off and solder in a new connector. People who tug on the wire to pull the connector out of a jack contribute to wire breaks at the connector - Never tug on the wire part of a cable to disconnect it. Get hold of the connector and pull it, not the wire. Stepping on a connector, while it is plugged in, or exerting sideways pull on a cable can cause the riveted parts of a connector to get loose - this is bad, as it now creates a loose connection that will eventually become worse over time. When this happens, cut the damaged connector off and throw it away - replacing it with a new one that is at least as good quality as the one you removed.

The wire inside the cable needs to retain its original design qualities, otherwise, its use will become unpredictable. While 90% of cable failures happen at the junction of the connector and the wire, the rest of the problems often end up somewhere within the wire itself - and in case you didn't notice, you usually can't see into the wire to find the damage. Wire is designed to have a specific electrical resistance and a specific capacitance for a given length of wire. The resistance can change if a wire gets stretched to the point where the wires inside actually start to break. The capacitance can change as the result of heavy things running over or being dropped onto the wire. These problems are amplified when you use sub-standard (junk) cabling. You want the lowest resistance possible as well as the lowest capacitance - you don't want to alter the characteristics of the wire, otherwise, the sound can change. This is far more an issue with low level audio cables (those used for microphones and musical instruments) than cables that are used to drive speaker cabinets, however, if you are paying for quality cables - you want to keep them functional.

Quality connectors

XLR connectors:

These are typically used in microphone circuits, and PA system cabling. Other applications for them appear, depending on what hardware you are using. The cables that use XLR's at both ends usually have a Male connector at one end, and a Female Connector at the other. The great benefit from this is that you can string these together by simply plugging a number of cables together. If used in Low Impedance settings, this does not cause much in the way of problems - cable length becomes more of an issue for high impedance circuits. Usually, there are 2 signal wires that connect to pins in the connector, where the last pin and the rest of the connector is the signal ground. There are a few different ways to correctly wire this cable, so if you are unsure, you may want to open up one end of a specific connector and mark down the which pins go to what. These don't normally see the abuse that 1/4 inch phone connectors do, but a crushed one will not work (it happens to the best of us).

RCA Phono Connectors:

Of all connectors that are prone to noise problems, this is probably the number one source of bad connections. These were originally designed to assemble component audio systems (long before Stereo). At that time, you would connect everything up, then you wouldn't touch anything for years, maybe even decades. These don't cost very much to make and builders of gear that might be hooked into an audio system that probably don't have to get re-wired frequently can easily get away with this form of connector. The problem I have experienced is that I'm often in a position that I have to use something that has these connectors on it and I will frequently be connecting and disconnecting everything. You can't solve this problem by using gold plated connectors, the problem is that a good signal connection depends upon a good friction fit of the connectors - over time the plug and the jack stop fitting well and you may be forced to replace the jacks that are mounted in the gear. This type of connector is usually destroyed if anyone steps on it. On some of my gear, I have replaced the RCA Phono Jacks with 1/4 inch Phone Jacks, or wired an RCA Phono Plug into a 1/4 inch Phone Jack, simply so I can use a more reliable connection method.

Other Connectors: There must be 50 different random audio connectors on the market. I have quite a collection of odd sized and very uncommon connectors (you should see the one on my early 1960s Shure Microphone - I defy you to find a replacement - I bought one in a surplus store in Los Angeles in 1975; they only had one left and I've never seen another for sale anywhere) The more common ones will be 1/8 inch monophonic and 1/8 inch stereo Phone connectors. There are smaller ones than this too. You will find that these connectors do not appear on gear designed for semi-professional or professional musical gear too often, but, never put it past the manufacturers to sneak one in where you would least expect it. Also, I sometimes use gear that was never intended for pro-audio use; you might find some gear that is musically quite useful for a recording or use in your music - these frequently have peculiar connectors on them.

Gold Plated Connectors: For the person who frequently plugs and unplugs connectors, the gold plating will wear off pretty quickly and in my opinion, you are wasting your money. If you are wiring up an assembly that the wiring never changes in, then you can use them. The benefit is that Gold does not tarnish and as such does have the potential of giving you a better electrical contact. I doubt that you will find many semi-pro and pro quality musicians gear that use gold plated connectors - these more typically appear on high end Audiophile home sound systems that don't get reconnected frequently. For the working musician, you really don't need Gold plated connectors for anything.

Wire

• Resistance
• Capacitance
• Inductance

All cable wire will color the signal (ie. alter the tone in some way) and usually this is a result of the resistance and capacitance of the wire - mostly the capacitance. To give you an analogy, the tone control of most guitars (ie. those without out an active pre-amp stage) use an variable resistor (the tone control) and a capacitor. The capacitor shunts (rolls off) high frequency audio and substantially alters the tone. Your audio cables have the same effect - every cable has some quantity of capacitance, and will roll off the high end frequencies to some degree. Your goal is to find wire with the least resistance and the lowest capacitance.

Resistance is typically measured per thousand feet (around 310 meters). Good wire will be under 100 ohms per 1000 feet. Capacitance is typically measured per foot, and the effect is additive as the cable gets longer. Good cable is typically under 100 pf (picofarads) per foot. Inductance of the wire will vary depending on how the wire is laying - of you leave it coiled up, the inductance will be higher than if you uncoil it. For this reason, you should use the appropriate length of wire for the given job and have different lengths in your cable box. Inductors are used in cross-over networks to roll off high frequency signals - ie, they are used to throw away high frequency signals and drive Woofers within thier specified frequency range.

Many semi-pro and professional microphones are low impedance - by that I mean the microphone is designed to connect to a pre-amp thats impedance runs at under 1000 ohms. High impedance input stages run from 20,000 ohms and up (usually 50,000 ohms or more). You need to match impedances with the gear. Low impedance connections tend to be lower noise and can use fairly long runs of cable (50 to 100 feet are not uncommon). High Impedance (which includes practically all guitars, electronic keyboards, Synth modules and outboard gear - such as stomp boxes) should all use the shortest cable runs possible (25 feet or less). I'm a great fan of wireless systems (I have 2 Nady systems), because they extend my guitar cable length without the restrictions associated with high impedance wire.

Low impedance cables typically have 2 conductors and a ground (2 central wires and a shield) - these are balanced connections.

High impedance cables typically have 1 conductor and a ground (1 central wire and a shield).

Speaker cables typically have 2 conductors and no shield.

The rule of where to use shielded wire and where not to is simple - any audio cable that drives speakers directly is not shielded. All other audio cables should be shielded.

If you are going to wire up a recording studio, I suggest that you scope out all of your cables and buy lowest resistance/capacitance you can find, and go out of your way to use the same cable through-out similar circuits in your system. For the average working musician, its unlikely that you will be able to afford to do the same thing - again, buy the best wire that you can afford.

Just so you don't think that you have to go broke buying cables, I have quite a few cables made using midrange shielded cable that originated from Radio Shack. These work fine, just keep in mind that Radio Shack sells a lot of low end wire products that are not intended for long runs or the level of abuse most musicians and vocalists will give them. These are fine for the hobbyist market - You get what you pay for.

For speaker cables, I find that 18, 16 and 14 gauge zip wire (depending on the length of the run and wattage of the system) works fine for small to midrange systems. I carry different lengths, trying to match the length to the need. Don't leave big coils of speaker wire anywhere when using speaker cables - this will reduce your high frequency response.

• If you are driving an audio system outputting under 500 watts RMS, and your speaker wire runs are under 100 feet, use 18 gauge zip cord.

• If you are under 500 watts RMS and greater than 100 feet, but under 250 feet of wire, use 16 gauge zip cord.

• If you are between 500 and 2000 watts RMS and under 100 feet of speaker wire runs, use 16 gauge zip cord.

• If you are between 500 and 2000 watts RMS and and greater than 100 feet, but under 250 feet of speaker wire runs, use 14 gauge wire (zip cord or other).

• If in excess of 2000 watts, you should refer to the documentation associated with your PA system power amplifiers and use what they reccomend.

Avoiding Ground Loops

Ground loops cause hum and other objectional noise in the signal path. If you are wiring up a rack mounted PA system with numerous outboard effects, it is likely that some of these connections will benefit from these specialized cables. The rule is simple, if you already are providing a ground connection from one device to another thru a normal cable, the rest of the cables used between the devices should be of the type where the shield is only connected on one of the ends. I don't know of any companies who make these up - you will probably have to make them up yourself.

Less Desirable Audio Cables

I find that cables with pre-molded connectors tend to fail with incredible regularity. I tend to use those that have RCA Phono Plug on them until they fail, then I replace them with a soldered on RCA Phono Plug. I don't reccomend ever using a cable with molded 1/4 inch Phone Plugs. In general - Plugs that are have molded ends may look nice, but they normally fail at the junction of the wire and connector.

Some low end cables use a kind of flimsy copper wire woven in with what looks like cotton or polyester - these have very poor shields and are very high capacitance - Even worse, they are un-repairable. If you ever encounter one after it has failed (these tend to fail very quickly), throw it out.

Cables that are self retracting (spiral wound) are often made of with the wire noted above (there are good quality versions, but these are not commonly available). While the self retracting quality is very nice to have, very few of them will last very long or have good sonic qualities. If they have molded ends, you can depend on them to fail quickly - the stress on these junctions is pretty high and the cable is always attempting to pull itself apart. It will eventually succeed. You may find quality cables of this nature, but they will be very expensive.

Some cables are not designed for high traffic audio applications - these then to have a shield that is a single strand of wire with a wrap of what appears to be aluminum foil around it. These don't handle flexing very well - they were designed to be mounted into a chassis, or stapled inside a wall - they will not hold up well unless used in an area where they are rarely unplugged or moved. In general, these also tend to become microphonic - this is where noise is generated within the cable itself and when it is moved or stepped on, it makes noise. You don't need this kind of problem.

I'm going to buy my cables, what should I buy?

Next, look at the connectors and see if they are flimsy or if they appear to be solid and heavy duty. Reject any that do not use all metal covers. Many will have heat-shrink tubing applied to reduce the stress on the connector/wire junctions. The wire should be reasonably heavy (as much as 1/4 inch thick for high impedance cables, sometimes a little thinner for low impedance cables with XLR connectors. Some of these cables have warenttees - this may be justification enough for buying a specific cable; if it breaks they will replace it. Does the cost justify this? You have to decide what its worth to you. High end cables are sold with the expectation that they will experience some rough handling, also the wire resistance and capacitance will be as low as possible.

I'm going make some of my cables, what should I buy?

The most difficult part seems to be stripping the wire and dealing with woven/braided shielding. There isn't space in this article to cover the joys of wire stripping, however once proficient, you can make cables that match exactly what you need. This is very useful if you need many short cables or specialty cables.

Always remember to slide the cover onto the end of the wire before you solder the connections; otherwise, you'll have to remove the connector to add the cover, then re-solder it again (I still do this occasionally - its quite irritating). Also verify that you slid the cover on the right way.

You should always use electrical tape around the wires that attach to the center taps of the connectors; avoiding short circuits in your cabling. Think about any stress points in the cable - use tape to provide additional connector/wire support where appropriate.

Simple guidelines

20 or 22 gauge works well for most single conductor sheilded low level signals (guitar or keyboard cables). Long runs of single conductor cable (more than 25 feet), can be a problem for low level signals like a guitar, but is not a problem for line level devices, like the output of a mixer (being connected to a power amp). Quality cable (for example, the brand Beldon is good, provided you get Audio cabling, and not cable for digital applications) makes a huge difference.

Any cable being used for speakers should not be sheilded, but rather be 2 or more conductors that are 18 guage wire or thicker. Thicker is better to a point, however its better to move the power amps closer to the speakers than to run longer speaker cables with heavy wires. If the speaker wiring is built into a wall (ie, not moveable), you can use solid wire (as used for house electrical wiring). In all other cases, it should be flexable/stranded wire. If you are using 14 gauge or heavier wire, you should not be using 1/4 inch jacks (they can only handle about 500 watts) - look at Speakons (these can handle 2000 watts) instead.

Speakons

General thoughts

If you have a cable that you depend on, and you only have one of them, rest assured, it will fail when you need it most (probably when a talent scout for a record company came just to hear you and is in the audience). I suggest that you have a spare for every type of cable that you have in your cable case. For a large PA system, you might need to carry as many as 100 cables. Even if you only play guitar or keyboards, it is a good idea to carry at least one spare cable for every cable you normally use.

I like to mark my cables with colored tape at the ends - this allows me to uniquely identify my cables - it also helps keep people from swiping your cables, or maybe swapping their bad one with your good one.

I have a bag that I throw dead cables in when I find them. This helps me track them after a practice or show and allows me to get them fixed. I usually have at least 50 audio cables with me at any one time - they all really look pretty much the same when you stare into your case trying to remember which grey or black cable was not working last Friday night.

A cheap ohm-meter is a valuable investment when it comes to tracing down problems in your cabling. It can be used to find short circuits and open circuits. Its also good to help figure out which wires go to a given set of pins on an XLR connector or a special connector that you may need to make a duplicate spare cable of.

Lastly, cables can turn out to be a substantial investment. I get real touchy about people not treating them well. You should too. Its easy to invest several hundred dollars in cables that can all be ruined by poor handling or lack of protection during transit. Its your money - take care of them.

NOTE: All wire gauges mentioned here are AWG - if you are outside the United States or use a different measurment, please see the SWG to AWG conversion table for more information.

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