Supply voltage and effective AWG question

[mk05]

Hello ASR, I have a couple questions.

1) If I have a system that comprises of a Modulus-686 stereo amp pushing ~130w into 8Ω, a DAC, and a pre-amp, how much power am I going to draw? My ~20yr old 4-outlet power strip is rated 1400 Joules (is that 1400w for how they "rate" these things?) with 10A protection and 6ft cord rated 16AWG. I read that a 6-outlet with 3000w rating and minimum 14AWG cord was advised, but wasn't sure how true that was. Is 10A too low for audio (but ok for practical app)? I see my other regular white plastic strip that is being used for my TV and other peripherals is rated 15A with 1800W. Could you tell me how much energy rating (for lack of better word) I am looking for, in terms of per outlet for high-fidelity recreation? As in 6 outlet vs 4 outlet vs 2 outlets power strips. Finally, I read that how the outlets are wired makes a difference - as in, it matters if the outlets are in daisy-chain or parallel. I recall in my readings that dip/sag in supply current (load current) cause increased output impedance which is bad, and also system damage (which is where I guess backup supply comes into play on those expensive conditioner or AC/DC power transfer). How much does this matter for power strips? Please correct me if I have this backwards or just horribly wrong.

2) I was going to build my own cables, since it seemed fun - but most importantly easy. I was looking at Carol 14/3 to make my own cables. Is this a good cable to make audio cables from? Is the effective AWG 14, or does this mean that there are 3 wires of 14, which means 9AWG?

As always, thank you for the advice.

 

[RayDunzl]

how much power am I going to draw?

50 watts would be a highish guess, unless you are blasting test tones at maximum output.

Get a tool:

http://www.p3international.com/products/p4460.html

Carol 14/3 is three strands of 14AWG.

Outlet strips are wired in parallel. "Daisy Chain" sounds like being wired in series, which they are not.

 

[Speedskater]

The 1400 Joules rating is for the surge protection function of the outlet strip. It's a momentary spike rating. Nothing to do with the continuous power rating.
The 10 & 15 Amp ratings are a 3 hour continuous power rating. That would be for heating elements or a large lighting system (lets skip the fine print).
A hi-fi system playing music only draws significant power during the peaks, so a 16AWG cord is OK for a rather large amplifier.

 

[mansr]

My ~20yr old 4-outlet power strip is rated 1400 Joules (is that 1400w for how they "rate" these things?) with 10A protection and 6ft cord rated 16AWG.

The joule is a unit of energy equal to one watt-second which makes no sense as a rating on a power strip, so let's assume it's actually 1400 W. Assuming you're in a 120 V country, 10 A is enough for 1200 W, leaving some margin in the rating.

Could you tell me how much energy rating (for lack of better word) I am looking for, in terms of per outlet for high-fidelity recreation?

You say your amp is specified at 130 W, which you're probably not using much of. Nevertheless, we can pretend you are and see where that leads. I'm guessing those 130 W are per channel for a total of 260 W. Being a class D amp, it's quite efficient, so assuming an input power of 500 W is probably erring on the safe side. Add a generous 50 W each for DAC and preamp and you're still only halfway to the 1200 W allowed by the 10 A rating. I wouldn't worry about it. In reality, you're probably, as Ray suggests, using less than 50 W total.

Finally, I read that how the outlets are wired makes a difference - as in, it matters if the outlets are in daisy-chain or parallel. I recall in my readings that dip/sag in supply current (load current) cause increased output impedance which is bad, and also system damage (which is where I guess backup supply comes into play on those expensive conditioner or AC/DC power transfer). How much does this matter for power strips?

Most power strips have a set of fat wires or copper/brass strips running down the length attached to each socket. Electrically, the sockets are of course connected in parallel. The resistance of this internal wiring is low, so it doesn't matter which loads are plugged into which sockets. The resistance in the power lead and the in-wall wiring does mean that a high-power load will cause a voltage drop. For example, my ~12 A kettle causes a 5 V drop when I turn it on. The power supplies in your audio devices are designed to handle such variations. They have to be since the mains voltage fluctuates at least that much over the course of a day anyway.

In short, your power strip is fine.

 

[mk05]

Thank you for the replies. I will stick with my current strip. Now purely for my curiosity,

Assuming you're in a 120 V country, 10 A is enough for 1200 W, leaving some margin in the rating.
...halfway to the 1200 W allowed by the 10 A rating.

What do you mean by enough in, "10A is enough for 1200W" (as in the example)? Is there any influence of the current being limited at 10A vs 15A on the connected components? I have seen even strips at 20A, for example. And what "watt" or joules rating should that have in a 120V country?

 

[mansr]

What do you mean by enough in, "10A is enough for 1200W" (as in the example)? Is there any influence of the current being limited at 10A vs 15A on the connected components? I have seen even strips at 20A, for example. And what "watt" or joules rating should that have in a 120V country?

Watts is volts times amps. Your voltage is fixed at 120 V, and the fuse limits the current to 10 A. That means the maximum power is 1200 W. If the connected load requires less than 10 A, a bigger fuse makes no difference. If it needs 12 A, say, then obviously the 10 A fuse would blow while a 15 A one would not.

For any piece of metal, there is a maximum current it can carry without heating up too much. This is independent of the voltage. A cable that is good up to 10 A can thus deliver at most 1200 W with 120 V mains. Over here, where we have 240 V mains, the same cable can safely deliver 2400 W without exceeding the 10 A limit.

 

[mk05]

If the connected load requires less than 10 A, a bigger fuse makes no difference. If it needs 12 A, say, then obviously the 10 A fuse would blow while a 15 A one would not.

For any piece of metal, there is a maximum current it can carry without heating up too much. This is independent of the voltage.

Thank you for the explanation. Continuing on this, how do I know the Amps I consume? Or is this rating from the supply side for protection?

 

[mansr]

Thank you for the explanation. Continuing on this, how do I know the Amps I consume? Or is this rating from the supply side for protection?

If you know how many watts you're using, you can get amps by dividing by the voltage. For example, 600 W at 120 V is 5 A.

 

[Speedskater]

In the US, you can buy a inexpensive "Kill-a-Watt" meter, to measure Volts, current & Watts.
Remember the way the AC main power system measures current is over a continuous 3 hour period. A rather large home theater system can operate on one 20 Amp circuit.

 

[TomB]

In the USA, daisy chaining is often a reference to how wall outlets are wired. The outlets have two sets of terminals and the easiest way to connect one outlet to another is to connect an outlet to the next outlet using the extra set of terminals. The more labor intensive manner would be pig-tailing each connection. Pig-tailing each outlet is preferable in my opinion, and offers distinct advantages. But both result in the outlets being wired in parallel.

 

[mk05]

In the US, you can buy a inexpensive "Kill-a-Watt" meter, to measure Volts, current & Watts.
Remember the way the AC main power system measures current is over a continuous 3 hour period. A rather large home theater system can operate on one 20 Amp circuit.

Thank you for explaining how to use the product that another member posted above. I wasn't sure how it related to my question.

How does brownout consider into all this?

I appreciate everyone's help!. Learn something new everyday!

 

[amirm]

An amplifier rated at 130 watts uses more AC power than audio power it produces (some gets lost to heat). You would need to know its efficiency or alternatively use the power meter to measure it (when fed a signal to produce the max power).

The AC mains produces volts and amps. In US, the former is nominally 120 volts. The amps are whatever they are. If the power strip is rated at 10 amps, then you have 1,200 volt amps, not watts. Conversion to watts requires knowing the power factor of the load. For a resistive load like a light bulb, power factor is nearly 1 so volt-amp = watts. For different loads, the power factor could range from 1 to much lower. If power factor is 0.5, then 1200 volt amps is just 600 watts. Some AC meters have power factor computation and can show this info for you.

Wire gauges are mandated by code:

20 amps = 12 gauge
15 amp = 14 gauge
10 amps = 18 gauge

But yes, what you have appears to be good enough for what you need.

 

[JustJones]

I assume these power strips are also surge protectors? If so the 20 year old one should be replaced I imagine the MOVs are degraded.

 

[RayDunzl]

Thank you for explaining how to use the product that another member posted above.

The meter shown will measure/calculate volts, watts, amperes, frequency, power factor, watt hours, running cost, etc.

It's a useful tool to investigate appliance power usage.

There are various similar devices: https://www.amazon.com/s?k=killawatt+ez&ref=nb_sb_noss_2

One or two watt years of usage saved will pay for it if you are "on the grid".

 

[MZKM]

Wire gauges are mandated by code:

20 amps = 12 gauge
15 amp = 14 gauge
10 amps = 18 gauge

But yes, what you have appears to be good enough for what you need.

For car audio I have seen people state using larger gauge based on wattage, but I never understood. What happens if you have a 6ft wire of 16awg and you use it to power speakers with a 1000W (8ohm) amp, and let’s assume the speaker can actually handle that?

 

[mansr]

For car audio I have seen people state using larger gauge based on wattage, but I never understood. What happens if you have a 6ft wire of 16awg and you use it to power speakers with a 1000W (8ohm) amp, and let’s assume the speaker can actually handle that?

Car audio runs off 12 V so you need 10x the current to reach the same power compared to 120 V mains.

 

[Wombat]

Do performance car systems not use switching power supplies to boost rail voltage?

 

[mansr]

Do performance car systems not use switching power supplies to boost rail voltage?

At some point they almost certainly do, but they're still powered by the car's 12 V supply. I don't think it would be a good idea to run high-voltage power cables down the length of a car. Could give someone a nasty surprise.

 

[tomtoo]

Do performance car systems not use switching power supplies to boost rail voltage?

They have to, lets imagine alien power amp's without any lose but follow ohms law.

P=U*U/R with a 8ohm speaker thats impressive 18Watts with 12V .

 

[raindance]

In my younger days I was asked to help a friend figure out why his 150 watt per channel amp in his car couldn't produce more volume than my 6 watt per channel system (a wonderful Pioneer component system driving very efficient Phillips 6x9 coax speakers under the rear floor of my van and a pair of small Pioneer 2 ways in the front doors).

He was tapping 12 volts for the power amp from an existing wiring loom in the trunk. When I measured actual power output, his system managed about 3-4 watts before the voltage collapsed. We added very thick, jumper cable style power leads from the trunk to the battery, and 150 watts was achieved, to the detriment of his hearing and his neighbors patience.