(C) 2015 Hank Wallace
Of late we have seen several high end power cords advertised as replacements for regular power cables sold with guitar amplifiers. Are they an improvement over the stock cords? Let’s check it out.
The first thing we see when looking at one of these high end cords is that they certainly look high quality. The molded plug generally has an enhanced grip that encourages you to pull the plug out of the wall socket using the grip rather than the cable! That’s a plus. You should never pull an AC plug out of a wall socket using the cable because it weakens the wired connections in the plug.
Some of these cable manufacturers advertise that the connections are not just crimped but soldered as well. This is good as a crimped connection is only as good as its assembly. As a person with many years experience in industrial electronics, I have found loads of crimped connections that were improperly crimped, later failing or becoming intermittent. This causes no end of grief until the culprit is located. Soldering a connection (even if initially crimped) causes the assembler to inspect the joint more closely during the soldering operation, resulting in a better connection and lower failure rate.
Generally, these high end power cords appear to be constructed well and serve their function adequately.
However, as with most music industry marketing material, there is a generous amount of hype which has no basis in fact. But it sure sounds important to guitar players, and that of course sells more product. When a technical expert looks at a situation, one of the things he looks for is some overriding condition or situation that makes moot other considerations that may otherwise be considered important. For example, if a doctor sees a 90 year old patient who is in decent health, and who smokes a cigarette or two per day, the doctor could nag the patient to stop smoking, but he realizes that the patient has not long to live anyway, so let him enjoy his smokes.
The overriding issue with high end power cords is that they are plugged into building electrical systems which by engineering standards are the height of trashy practice. For example, there is no shielding whatsoever on electrical wires between your wall outlet and the source of the energy, say a hydroelectric dam or coal fired power plant. None. We’re talking perhaps hundreds of miles! So why shield the last four feet of wire?
Most wall outlets these days do not use screw terminals to connect to the house wiring, but rather use push-in connections that grip the wire using one or two small blades of metal. Those connections are high resistance, compared to the rest of the wiring (though still less than an ohm). I would never find a respectable amp designer using such a connection method inside a guitar or bass amp.
Further, most house wiring in the USA is 14 gauge copper wire, sometimes 12 gauge. It makes no sense to connect a thicker gauge of wire in a high end power cord to a run of 50 to 100 feet of 14 gauge wire stretching back to the breaker box! That long run of cheap wire (also NOT oxygen free!) is the overriding condition.
Let’s look at some of the manufacturer’s claims.
- Oxygen Free Copper. This is covered in our article, What About Gold Connectors and Oxygen Free Copper?.
- Shielding. If the electrical cable going all the way back to the power plant is not shielded, why shield the last few feet? In a rack, all the other signal cables are shielded, and with proper cable dressing there is no crosstalk. Shielded power cables are sold commercially, but they are intended to prevent equipment from radiating noise.
- Wishy-washy terms, such as high frequency rolloff, phase distortion, speed of power delivery, impedance disturbances, etc. As long as the power cord has sufficient copper, at least the gauge used in the building wiring (14 to 12 gauge), none of these effects are material. The power supplies in tube amps consist of a transformer, some diodes, and a few capacitors that filter the rectified voltages. All high frequency information is lost in the capacitors. Any ‘phase distortion’ is eliminated by the capacitors (as if a power cord could correct or cause phase distortion anyway). The impedance of the power cord is totally irrelevant as it’s plugged into a power system where the impedance varies wildly.
So what’s important? Buy a power cord that is physically sturdy, with substantial prongs. Use the shortest cord that is convenient. A cord should have at least 14 to 12 gauge wire, with the smaller number having more copper. A power cord should have soldered connections and a good strain relief to stand up to cranky roadies at the end of the night.
Note that a lot of the standard power cords shipped with guitar amps contain 16 gauge wire. Also, note that a 100 watt head draws about 1.6 amps at full power from a 120VAC circuit. That’s not a lot of current (considering you are plugging into a 15-20 amp circuit). Using a thicker wire gauge will reduce the cable’s resistance some, but of course the cable will also be stronger. Premium cords may indeed be an improvement over stock cords just because they contain more copper, but they may not be worth the extra money.
Following these recommendations, you will find a decent power cord that will not starve your amp of electrons, and you’ll have some money left over to change your strings a few times!