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10 comments / Posted by Bruce Ohms

Instrument Cable

 Even the most experienced musicians forget essential parts of their rig from time to time. A drummer I know forgot his drum sticks at an out of town gig, and I myself have showed up to play at a local show having forgotten to bring my bass amp head (I had to use a DI that night)! It’s something that happens to the best of us. Fortunately, if there are other bands on the lineup or a helpful soundman, they may be obliged to help you out lending you the item you forgot, especially if it is something like a cable.

Use the Right Cable for the Job

If you’re at the gig or studio and realize that you’ve made the understandable mistake of forgetting your speaker or instrument cables, or you’ve found out one has gone bad, it’s essential to make sure that the new one that you borrow or buy is the proper one for the job. While standard ¼-inch speaker and instrument cables may look similar, they have a few key differences in construction that make it so you cannot use them interchangeably.

The construction is fairly simple. It consists of a copper core coated with polyester or rubber, with nickel, gold, or other metal connectors. High-end cables like Carvin Audio’s C20P shielded guitar cable utilize an oxygen free copper core for optimal signal transfer and to reduce the aging process of the copper. The key difference between instrument and speaker cables are instrument cables are shielded with much smaller wires and speaker cables are unshielded with larger wire gauges.

Since an instrument cable is used to connect your instrument to the amplifier in a high impedance environment, shielding is essential. Shielding surrounds the signal wire in and “shields” it, reducing interference from other electronics and radio signals nearby. Speaker cables do not need shielding since the signal from your amp is so large and the impedance of your speaker is so low, that any additional RF noise and outside interference will be insignificant.

What Happens if You Use the Wrong Cable?

Using a speaker cable in place of an instrument cable will add a lot of unwanted noise to your setup. Since it’s unshielded, your guitar signal will be accompanied by buzz, hum, and interference from the surrounding electronics- including hum and buzz from your own amplifier’s transformer, your band mates’ amplifier and the PA speakers. Not to exclude the lighting system, cell phones and those cool beer neon signs hanging all around the bar. You’ll be a one person noise rock band, and not in a good way.

Using an instrument cable in place of your speaker cable can cause catastrophic damage to your amplifier. While your amp will still work initially, the high amount of current going through the instrument cable’s small gauge wire can actually melt the cable! Furthermore, this may cause a short, damaging your amplifier.

Another issue with using shielded cables for speaker cables is they introduce a capacitive element that can destabilize your amplifier. Most amplifiers have improved to withstand using the wrong type of cable for a short time, but no one likes to test their amplifier’s stability at a show. This can cause some crazy results in some amps leaving it damaged and you paying the repair bill.

Telling the Two Cables Apart

While most manufacturers make it clear which one is which by labelling it clearly on the cable, there may be instances where you won’t be sure. If this is the case, simply unscrew an end of it. A speaker cable has two independent wires, one connected to the tip and one to the sleeve. These wires will likely be red and black or white and black. There should be no braided wires or a foil rap present let alone connected to any pin. The two wires should be of significant size also. Typical wire gauge for a 1/4-inch speaker cable is 16 or maybe 18 gauge. If it’s an instrument cable, you will see one or two wires covered in some form of shielding. The shielding can be a braided wire mesh or foil wrap around the one or two wires. If the ¼-inch connector is a TRS end (this is a stereo end with a Tip, Ring, and Sleeve, like on head phones) then you know it is not a speaker cable.

If you’re in a bind, make sure you use the proper cable! While it’s easy to be tempted to substitute one for the other, it’s never worth it.


  • Posted On September 26, 2016 by Cecille

    What cable should be used to connect a speaker to a mixer?

  • Posted On July 20, 2016 by Jim King

    Thank you! I’ve wondered about this for years. I’m going straight down to my sound cellar and label all my cables today.

  • Posted On July 13, 2016 by David Gibeley

    Speaker cables really should have insulation around the metal knurled part of the plug. Amplifier outputs are often bridged, and there can be significant DC voltage present on the outer conductor. If you grab it while touching anything grounded, you are going to get a jolt. Put heat-shrink tubing over the metal knurled part for safety.

  • Posted On May 30, 2016 by Paul

    Very helpful article. Explains some of the issues we are having when our band practices in basement. Hums, proximity to each other, stepping on cables, etc. keep the information coming. I enjoy all my Carvin stuff!!!

  • Posted On May 27, 2016 by luther (Lu) allen

    my carvin 1200 amp …amp 1 is down (low)…what is good temporary amp to use to power my 4.10s and 1.15 speakers until my carvin is repaired?

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