How much electricity is used by class A amps?

[russel]

I am sure you have a rationale for that claim.

Its a lot more difficult to bog up a class A design, although some people seem to manage.

 

[stevec67]

I'm currently attempting to solder together a Class A JLH design, it's simpler than others I have seen but I am confident in my ability to bugger up its construction at some point. Watch this space.

 

[Arkless Electronics]

I had simplistically assumed that the level of standing current would give you a reasonable idea of power consumption - my SE class A power amp (16wpc) has 2A of standing current, so I had always assumed something in the region of 2x240 = 480w consumption, or approx 1 unit every 2 hours - is this completely wrong/optimistic?

Completely wrong yes! We need to know the voltages powering the actual amp boards to get to a rough estimate here..

 

[Arkless Electronics]

My Lk280/sparks consume 25w per channel quiescent.

So eight channels is 200w.

That works out at 24*200*365/1000 kwh

At 11p per kwh that's almost £200 per year

And that's class a/b

I very much doubt that...

 

[mercalia]

Only the rich can afford "Class A" says it all really.

 

[Johnny2Bad]

This is a very simple question to answer.

1 KwH is 1000 watts of electricity used for 60 full continuous minutes.

Your power bill is measured in KwH. So if your electricity costs 10 pence per KwH, that's what you pay under the following examples.

Every appliance and component has listed, right on the unit by the power inlet, the consumption in watts. It's there for a reason.

So if it uses 100 watts, it will use 1 KwH after 10 hours of continuous use (1/10th of a KwH). And it costs a pence an hour to run.

If you have a 60 watt light bulb, it will use 1KwH of electricity if left on for 16 hours 40 minutes (16.66 hours). That's 1000 divided by 60. And it costs 6/10ths of a pence to operate continuously for one hour.

See how easy this is?

A real-world Class A example: Pass Labs XA30.8, power consumption 400 watts, so at 10p KwH would cost 4p per hour to operate at idle (the highest power consumption mode).

Now, *EVERYBODY* should know this stuff. If only so you don't exceed the capacity of an outlet, which can (if you're lucky) cause breakers to trip or (if you're unlucky) burn your house down.

Your children (as soon as they are old enough) and your wife or husband should know to add up the wattages of everything plugged into the same circuit that will ever be run simultaneously. If it adds up to more than your outlet is rated for, you have to remove something and you can't add anything else.

Don't think for a moment that if an outlet is rated for X watts, it won't deliver more than that. Not only will it, it will try it's hardest to deliver any load you put on it. Breakers (and fuses) are not truly wattage sensing devices ... in fact they have no idea whatsoever how much power is going through the line. They measure heat and heat alone. Pray that they measure the increased heat (which is *supposed to* correspond to watts, but doesn't really) and trip before the fire inside your walls start.

Overusing an outlet will work for a while, but the wiring in your home will light up pretty much exactly like a conventional stove element will if you ask it to. So you hope that the breaker tripped before the combustibles inside your walls light up, and burn your house down.

As competent AV installers like to say ... "I hope everybody got out".

 

[Mike Reed]

Well, it's just as well that I've got 8 directly coupled radials ending in individual RCBOs and c.u., though my nearly all-valved system hardly warrants it nowadays. It's nice to be safe, but that wasn't my initial priority reason, having a relatively recently re-wired house.

Good advice above to the uninitiated , but I got the impression that the preceding posts, by and large, were by dyed in the wool audiophiles and engineers. Not always the case, though.

 

[Minio]

An amp consuming 1kw per hour would kick out quite a bit of heat.

An amp like that would be very unlikely to be found in a domestic setting.

When I had a Musical Fidelity A1 it consumed around 50 watts which was about half as much again of a typical class B type amp, as measured with above mentioned gadget.

Some modern amps like Naim Nait or Creek amps consume only single figures like 7 watts.

 

[stevec67]

Only the rich can afford "Class A" says it all really.

Not really. The JLH I am building will consume about 70 watts across 2 channels and deliver 10Wpc. I have table lamps that consume that much. My planet-devouring halogen spots in the kitchen consume abou

This is a very simple question to answer.

1 KwH is 1000 watts of electricity used for 60 full continuous minutes.

Your power bill is measured in KwH. So if your electricity costs 10 pence per KwH, that's what you pay under the following examples.

Every appliance and component has listed, right on the unit by the power inlet, the consumption in watts. It's there for a reason.

So if it uses 100 watts, it will use 1 KwH after 10 hours of continuous use (1/10th of a KwH). And it costs a pence an hour to run.

If you have a 60 watt light bulb, it will use 1KwH of electricity if left on for 16 hours 40 minutes (16.66 hours). That's 1000 divided by 60. And it costs 6/10ths of a pence to operate continuously for one hour.

See how easy this is?

A real-world Class A example: Pass Labs XA30.8, power consumption 400 watts, so at 10p KwH would cost 4p per hour to operate at idle (the highest power consumption mode).

Now, *EVERYBODY* should know this stuff. If only so you don't exceed the capacity of an outlet, which can (if you're lucky) cause breakers to trip or (if you're unlucky) burn your house down.

Your children (as soon as they are old enough) and your wife or husband should know to add up the wattages of everything plugged into the same circuit that will ever be run simultaneously. If it adds up to more than your outlet is rated for, you have to remove something and you can't add anything else.

Don't think for a moment that if an outlet is rated for X watts, it won't deliver more than that. Not only will it, it will try it's hardest to deliver any load you put on it. Breakers (and fuses) are not truly wattage sensing devices ... in fact they have no idea whatsoever how much power is going through the line. They measure heat and heat alone. Pray that they measure the increased heat (which is *supposed to* correspond to watts, but doesn't really) and trip before the fire inside your walls start.

Overusing an outlet will work for a while, but the wiring in your home will light up pretty much exactly like a conventional stove element will if you ask it to. So you hope that the breaker tripped before the combustibles inside your walls light up, and burn your house down.

Don't be silly, this is the point of having fuses or breakers. If you overload the system the breaker trips long before the wires catch fire. That's what it's there for. A 2.5 t+e ring will do 30A, you fit a 30A breaker. The wires will actually do 35A day and night until hell freezes over, but the breaker will call a halt before then. Of course you could plug in kettles and fan heaters to get to 40A but the IEE are engineers and they have thought it through so you can't burn the house down if the place has approved breakers or fuses. I know this at first hand, the garage sockets are only 5A and every so often I get ambitious. Guess what? The breaker goes click and everything stops.

 

[davidsrsb]

.........Some modern amps like Naim Nait or Creek amps consume only single figures like 7 watts.

Naim designs have traditionally been at almost class B, with close to the theoretical quiescent current of a few mA.
Older Creels were mosfet, so had a much higher quiescent.
My previous Cambridge 640A ran two hot to leave on for too long, now my Yamaha AS701 runs cool.

 

[Johnny2Bad]

[QUOTE="stevec67]

Don't be silly, this is the point of having fuses or breakers. If you overload the system the breaker trips long before the wires catch fire. That's what it's there for. A 2.5 t+e ring will do 30A, you fit a 30A breaker. The wires will actually do 35A day and night until hell freezes over, but the breaker will call a halt before then. Of course you could plug in kettles and fan heaters to get to 40A but the IEE are engineers and they have thought it through so you can't burn the house down if the place has approved breakers or fuses. I know this at first hand, the garage sockets are only 5A and every so often I get ambitious. Guess what? The breaker goes click and everything stops.[/QUOTE]

You do know that every time you trip a breaker it degrades, right? Hope your 5A garage breakers are still in spec, but chances are they are not.

There are literally millions of homes that don't experience fires from electrical malfunctions. And then there are one or two that do. Are you going to burn your house down from abusing the service ratings? Probably not. Could you? Absolutely.

One UK government source I read suggested that if your panel is more than 20 years old, it can't be relied upon to protect the circuit from overload. (I personally find that a bit alarmist, but there you go).

Like the installers say (because they see the power kludges people use with AV systems) ... hope everybody gets out. About 40 people in the UK don't, every year (electricity caused fires only).

i'll even help you calculate the risks.

UK Electrical Fires 2015/2016
Total: 15,432
Injuries (includes fatalities): 1380
Average of 27 a week and 4 a day

2,920 caused by electrical wiring, cabling, plugs, injuring or killing 379 people. A significantly larger number are caused by misuse of appliances, but we don't know how many of those are audio or video related.

Personally when i'm feeling lucky I buy a lottery ticket, not overload my electrical system. And remember, some people DO win the lottery.

https://www.electricalsafetyfirst.org.uk/what-we-do/policies-and-research/statistics-england/

 

[david ellwood]

I'd just like to add that a 13a plug will not take full load continuously. Depending upon how well it is put together. I wouldn't stray above 10a continuous. 3kw heaters belong on a 16a ceeform. It doesn't help that a 13a fuse will happily take 20a for quite some time before blowing.

 

[Mike Reed]

I know this at first hand, the garage sockets are only 5A and every so often I get ambitious. Guess what? The breaker goes click and everything stops.

Not bloody surprised ! (Sorry !)

There is a difference between fuses and MCBs, i.m.e. The former are/were much slower to react and could affect the holder if a big bang. Not to mention the hassle of wondering where you kept the fuse wire card !

 

[Mike Reed]

You do know that every time you trip a breaker it degrades, right? Hope your 5A garage breakers are still in spec, but chances are they are not.

Didn't know that; interesting. Why then, it occurs to me, do the manufacturers recommend that you trip the MCBs/RCDs/RCBOs every now and again (6 months?) to test. Is this a clever ploy? Somehow I doubt it. I certainly can't recall reading anything in the literature which accompanied my breakers of their degradation by use. Hmmm! Must hunt out that literature, though I cannot doubt this new info., if only that everything fails eventually and these are very sensitivity specific items

 

[Johnny2Bad]

Didn't know that; interesting. Why then, it occurs to me, do the manufacturers recommend that you trip the MCBs/RCDs/RCBOs every now and again (6 months?) to test. Is this a clever ploy? Somehow I doubt it. I certainly can't recall reading anything in the literature which accompanied my breakers of their degradation by use. Hmmm! Must hunt out that literature, though I cannot doubt this new info., if only that everything fails eventually and these are very sensitivity specific items

Manually tripping a breaker isn't the same as the breaker tripping from heat. You can exercise your breakers as much as you feel comfortable with, but when one trips from sensing an electrical overload over multiple occurrences then you get into a failure mode of the heat sensing capacity.

The advice to test breakers is because doing so will generally clean up a corroded contact which might increase the resistance of the breaker elements. Corrosion can cause switches, relays and similar to fuse closed in extreme circumstances.

Breakers are very reliable devices, but they do fail. The indication of a need for replacement is when it trips at lower currents than it is rated for. So if you reset the breaker and it trips a second time that is a warning sign.

For very large overloads (short circuits) the expected life can be as low as two tripping events. In many cases they would continue to protect beyond those two events, but possibly not. Also the service life is typically rated at 30 to 40 years, so many homes are using breakers that have exceeded their safe design lifetime.

The capacity to safely operate is defined by IEC 947-2 which is adopted (almost) worldwide by national electrical codes (UK adopts it). Your product literature with a new breaker would state that the breaker is compliant to that standard, but typically would not elaborate as to what exactly that means.

http://electrical-engineering-porta...LV-circuit-breakers-to-standard-IEC-947-2.pdf

As I said, they are very reliable devices - they fail in a "safe mode" (trip while passing less current than rated) except under a very few conditions where they may fail to operate at all. That point would be reached if the warning signs are ignored. But they are not indestructible, nor do they have infinite lifespans in service.

The one point which I think should be emphasized is that they are not precision protective devices with regard to how much current they will allow before tripping. A 15A breaker is not a device that will allow 14.9A all day long but will trip at 15.1A instantly. If they actually worked that way most appliances with a motor (refrigerators, air conditioners, etc) would trip breakers often as the start loads are high versus the operating loads*. Annoyance tripping invites poor practices.

That is not how they function. Also I think the important thing is to know how to add up loads and maintain a safe total load on any one circuit. If you do that there is little risk of problems.

* One appliance that is more commonly being used in homes versus offices today are laser printers. They have start loads that are 2x or more the operating load in watts.

 

[Mike Reed]

Thanks for that; useful stuff. With RCBOs on my hifi ( MCBs + RCD on domestic c.u.) I'd not know which part had tripped ! Only happened once in a decade, though, so no worries.