Power cords

[JimChjones]

I've seen discussion about not only the power cabling, but also the head-to-cab amp cable. Some here have attested quite vigorously that a 1/4" speaker cable can't handle more than, say, 400 or 500W.

The problem is not the cable, but the connector. 1/4 in jack plugs were originally designed for signal level power. I just looked up their website, and apparently Neutrik jack plugs are rated for <50V, and Neutrik sockets 3A. Both figures can be exceeded quite handily by higher power amps. As for the power ratings of cheaper plugs and sockets, well I dread to think!

Its the first time I've actually looked up the power ratings of jacks, and 50V * 3A is a scarily low figure in watts. I'm glad I converted my gear to use Speakon.

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[1958Bassman]

I wish I could go back in time, to the days before all of these power/audio/video cable claims began and warn people that it's coming, to ignore it and to prevent Noel Lee & others from becoming very wealthy at the expense of peoples' lack of knowledge about electricity. I was hanging out with a couple of guys I had worked with at a stereo store and they were service techs- I had moved on to another place that only did car audio & security and I had been seeing comments about the "audiopile" grade cables and fuses, so I commented that we should gold-plate some and see if they sell. We laughed and laughed but less than six months later, someone started selling them and made a bundle.

I keep telling myself that it's good to have a clear conscience.

 

[1958Bassman]

The problem is not the cable, but the connector. 1/4 in jack plugs were originally designed for signal level power. I just looked up their website, and apparently Neutrik jack plugs are rated for <50V, and Neutrik sockets 3A. Both figures can be exceeded quite handily by higher power amps. As for the power ratings of cheaper plugs and sockets, well I dread to think!

Its the first time I've actually looked up the power ratings of jacks, and 50V * 3A is a scarily low figure in watts. I'm glad I converted my gear to use Speakon.

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I don't think I would call it 'scarily low', but if you use the power formula and consider impedance, 50VAC into 4 Ohms comes out to 625W-ish.

 

[dbase]

There has been some discussion here recently about 1/4" plugs and their ability to handle power, and so power handling was on my mind today as I was cleaning gaffer tape adhesive gunk off of some of my power cords.

I started looking at the information printed on the side of the cable, and I was startled to learn that the outward diameter of the cable was not a reliable indicator of the power handling! I'm sure that's old news for a lot of you, but it took me by surprise, and there might be a few of you that didn't already know this.
View attachment 4322669
The conductors in those cords are, from left to right, 18AWG, 16AWG, 14AWG, 14AWG, and 18AWG.

I can't count the number of times I plugged my amp in using a wider cord because I thought it would handle the power better. Granted, my amp doesn't draw enough to stress the thinner conductors, and all my lights have LEDs, so I was never putting myself in danger by doing this, but my ignorance could have had consequences if I had equipment that drew more power.

My Mesa WD800 came with a power cord the thickness of welding cable... I asked Agedhorse if I could use a regular computer AC cord and he said it was fine .. been using it ever since.

 

[downunder]

I used to have a GKMB150 Combo. I don’t remember the rating but I tried using a thin power cord that just didn’t work very well. The sound actually broke up and distorted. When I figured out the problem and went to a fatter one it worked fine. Ever since then I’ve trued to use The thickest power cords I can find. So I’ll have to look a little closer I guess.

 

[40Hz]

I just use the power cords that came with the product, use appropriately gauged extensions if necessary when gigging, and try to keep them as short as is practical. And I’ve never once had a problem. Am I alone in that?

 

[Real Soon]

What are you talking about, most of what you posted makes no sense whatsoever.

It was really late for me, I'll revisit.

 

[braud357]

I cannot believe that some people worry about this - and, trust me - I will NEVER buy one of those "high'dollar" power cables !

 

[Ostie]

I like a 10-gauge for goose, but for most other critters, I find that a 12-gauge is sufficient.

 

[Ross W. Lovell]

Reciting my electrical engineering mantra:
Using an oversized (vs. factory-supplied cable) power cable has no benefit. In fact, the weight and stiffness of too-large can damage your amp by causing severe strain at the mains connector.

The 18 AWG IEC cable typically supplied with amps has ample ampacity. It’s capable of handling several times the amplifier’s maximum current draw.

OK, that’s enough spitting into the wind for this week.

Don't agree.

Factory supplied is dictated by load and cost per cord.

I run 12-14 awg, mainly because if there is a low voltage situation, I don't want the cord "warming up".

The low voltage will be seen by an excessive draw on the main circuit and pop the fuse it breaker.

Never seen a mains connector built and dedicated to a wire size, just a load rating and those are designated by NEMA.

You have seen plugs and receptacles for 15/20 and 30 amp loads. You see them in AC units and other devices.

Amps use conventional units rated for a NEMA range that EXPRESSLY uses the proper NEMA plug and receptacle design, not, the cords amperage capacity.

 

[Jeff Scott]

I’ve evolved beyond gauge.

You now go by waist size?

 

[clockworkcorpse]

I don't think I would call it 'scarily low', but if you use the power formula and consider impedance, 50VAC into 4 Ohms comes out to 625W-ish.

you're missing half the formula there. you need to use a jack and socket together, so it would be limited by both ratings. voltage rating multiplied by current rating would be the maximum power rating.

 

[Engle]

Don't agree.

Factory supplied is dictated by load and cost per cord.

I run 12-14 awg, mainly because if there is a low voltage situation, I don't want the cord "warming up".

The low voltage will be seen by an excessive draw on the main circuit and pop the fuse it breaker.

Never seen a mains connector built and dedicated to a wire size, just a load rating and those are designated by NEMA.

You have seen plugs and receptacles for 15/20 and 30 amp loads. You see them in AC units and other devices.

Amps use conventional units rated for a NEMA range that EXPRESSLY uses the proper NEMA plug and receptacle design, not, the cords amperage capacity.

Please explain how the power cord could warm up if the supply voltage sagged. I think you are saying if the voltage drops, and the amp continues to draw the same amount of power, the current must go up. And this will exceed the current rating of the power cord.
But let’s see the math to support your statement.

 

[clockworkcorpse]

Please explain how the power cord could warm up if the supply voltage sagged. I think you are saying if the voltage drops, and the amp continues to draw the same amount of power, the current must go up. And this will exceed the current rating of the power cord.
But let’s see the math to support your statement.

it's actually kinda true, but only certain devices, like motors, will "pull" more current when voltage drops. watts is volts multiplied by current, so if voltage drops, current has to be increased to get the same watts.

 

[MuthaFunk]

I've seen discussion about not only the power cabling, but also the head-to-cab amp cable. Some here have attested quite vigorously that a 1/4" speaker cable can't handle more than, say, 400 or 500W. The specifics escape me, but it was in that area. And the informed conclusions were that the 1/4" cable connection have absolutely zero problem handling any market-available juice.

As an example, my Quilter BB800 has 1/4" out, and it's rated at 800W RMS at 4 ohms. And Mr. Pat Quilter knows that daisychaining cabs is common, so would not have included a 1/4" output if it posed a danger. This, however, is a combo of tangent and red herring. Also, audio cables, not really measured by gauge, are waaaay higher in estimated gauge (meaning way thinner), and they're not safe for high-wattage transmission. There's a point where copper thickness matters, but it's not at 12 or 14 gauge. It'd be like, what, 40 gauge? 60 gauge?

As for the original thing, power cords... I look at it like this. An 18-ga extension cord at Kroger or Food Lion or Piggly Wiggly or wherever may not be of the same build quality as something APC puts out. But a known reputable maker of power cords will have cords rated for uses faaaaar outstripping us running our bass amp setup. Like, they're looking at generators and pro light rigs and extra-output boat motors and things. 18-gauge.

Whoever actually needs 12-gauge copper connections is probably also hardwiring conduit. Bass & guitar amps and a space heater all at once. 30 amps at 120V kind of thing.

This is hilarious!!!

 

[agedhorse]

I don't think I would call it 'scarily low', but if you use the power formula and consider impedance, 50VAC into 4 Ohms comes out to 625W-ish.

Do the same calculation using current rather than voltage and you will see the other limiting factor.

I used to have a GKMB150 Combo. I don’t remember the rating but I tried using a thin power cord that just didn’t work very well. The sound actually broke up and distorted. When I figured out the problem and went to a fatter one it worked fine. Ever since then I’ve trued to use The thickest power cords I can find. So I’ll have to look a little closer I guess.

Sounds like something was defective, most certainly not due to the wire gauge.

Don't agree.

Factory supplied is dictated by load and cost per cord.

I run 12-14 awg, mainly because if there is a low voltage situation, I don't want the cord "warming up".

The low voltage will be seen by an excessive draw on the main circuit and pop the fuse it breaker.

Never seen a mains connector built and dedicated to a wire size, just a load rating and those are designated by NEMA.

You have seen plugs and receptacles for 15/20 and 30 amp loads. You see them in AC units and other devices.

Amps use conventional units rated for a NEMA range that EXPRESSLY uses the proper NEMA plug and receptacle design, not, the cords amperage capacity.

Factory supplied power cords supplied are generally independent not chosen based on cost. They are chosen based on the minimum required gauge, length, jacket requirements for the application, flexibility and safety agency global approvals.

If there is a “low voltage situation”, the cord won’t warm up, nor will it “pop fuses”. Please review Ohm’s law regarding non-rotating (non-motor) loads.

On conventional power supply amps, the cord will theoretically run cooler. Even on few amps with PWM regulated power supplies, the current only increased by about 12% at 100V which would rest in an unmeasurable theoretical increase in temperature. The agency approvals include under-voltage testing to -10% at 120V (~108V) for US market products and -10% for Japanese market products (~90V).

NEMA and the NEC has nothing to do with power cord sizing for plug connected devices. That is covered under UL 60065 and UL 63368 in the US market, which specifies the gauge for the current profile that the regulations define, the ground bonding and over current protection in the equipment, and other aspects of isolation and consumer safety as it applies to the equipment.

The supply capacity and NEMA connectors (type and current) are defined so that when the manufacturer provides or specifies a plug connected connection, the supply will confirm to the safety listing details that the equipment is designed and approved to. (Voltage, current, phase, configuration, and grounding).

I have dealt with this my entire professional life, industrial controls and power systems was the specialty of my EE degree. It applies very much to audio electronics as well.

 

[agedhorse]

it's actually kinda true, but only certain devices, like motors, will "pull" more current when voltage drops. watts is volts multiplied by current, so if voltage drops, current has to be increased to get the same watts.

Only for a constant mechanical load like a motor. The mechanism is a bit complicated, but a rotating motor creates back emf, which opposes current draw, when the voltage, the motor tries to slow down, the slip angle increases, the back emf is decreased so the current increases to try to keep the speed constant. This does not apply the same to fan loads (and a few other loads) where the load on the motor changes with the square or cube of the speed) and also depends on the motor type.

If you reduce the current to an amplifier with a non-regulated supply, the current DECREASES because there is no feedback mechanism like what most motors have. When the power supply is PWM regulated, that’s a form of feedback and will behave more like a motor.

This is a complicated topic, and shows why making simplistic and broad sweeping claims about power cords without understanding the underlying science/math is really pretty foolish. All the important information is in the details.

 

[Engle]

it's actually kinda true, but only certain devices, like motors, will "pull" more current when voltage drops. watts is volts multiplied by current, so if voltage drops, current has to be increased to get the same watts.

Even if the amp acted like a motor and pulled more current, the voltage couldn’t drop enough (within the range that the amp could still function)to cause the current to heat an 18awg cable.

If the voltage supply is sagging to those extents, that 18awg power cord is the least of your problems.

 

[lug]

All I know is some guy named Eddy is responsible for this and we should beat his ash.

 

[agedhorse]

Even if the amp acted like a motor and pulled more current, the voltage couldn’t drop enough (within the range that the amp could still function)to cause the current to heat an 18awg cable.

If the voltage supply is sagging to those extents, that 18awg power cord is the least of your problems.

Agreed.