measuring subwoofer idle power consumption

[wgscott]

I have a Rel Serie R-218 with a Class D amp. One of the reasons I wanted this was because of its "negligible" power consumption when left on but idle.

 

I noticed after being idle for 24 hours the back plate was quite warm.

 

I decided to measure power consumption, so I unplugged everything, then plugged it into one of those kill-o-watt meter things and into the wall.

 

It appears to consume about 50 Watts idle.

 

However, I also noticed the sub was emitting a rapid very low frequency signal when I had it plugged into the kill-o-watt thingie, making me wondering if the measurement device was interfering with the measurement.

 

WTF?

 

[Brian A]

Very cool. Never heard of the Kill-a-Watt thingie. Me want one.

 

I've been looking at clamp meters which do the same thing by measuring amperage. The difficulty is that the "clamp" can only go around one of the two power leads. Easily solved, but the Kill-a-Watt is simpler.

 

I can't imagine how the Kill-a-Watt is affecting the measurement, but stranger things can happen.

 

[wgscott]

You can get it for about $20 at Home Depot. It helps to figure out what appliances are reaming you.

 

The sub makes a rapid low-frequency thumping noise when plugged into it, and it takes power to do that, so in that sense it does seem to be interfering.

 

[Brian A]

Evidently. Hummm. Sounds like it may be pulsing on and off to measure current. Double hummm.

 

A clamp meter would solve it, but the cheapest I found are still pricy.

http://www.sears.com/shc/s/p_10153_12605_03482372000P?mv=rr

 

You'd need to buy a cheapie extension cord which allows you to seperate the two leads so that you can clamp around one of them.

 

[esldude]

I suppose it somehow could be causing hum or such. Assuming that class D amp is no less than 70% efficient then you must be putting out at least a 30-35 watt signal.

 

Things to try:

 

At the audio signal input to the amp use a shorting plug. (I am NOT talking about shorting the AC connection-sorry I know you are not stupid, just want to be very clear for anyone else looking in on this)

 

Use one of those cheater plugs for measurement purposes. The kind of plug lets a two pin power cable plug into a 3 prong plug. See if breaking a ground loop helps. This might also be combined with not having a connection to amp input.

 

If you have a power strip with surge and noise suppression plug the Kill-a-watt into the wall, the strip into the Kill-A-Watt and then the sub amp into the strip. Maybe it will separate whatever is picking up garbage from the other piece of electronics.

 

Either with or without the suppression power strip, use a long extension cord to plug the kill-a-watt into a different part of your house wiring at a distance of several more feet away. This way the Kill-a-watt is several feet away from the switching amp and any high frequency garbage from one unit to the other is also several feet away.

 

[1audio]

I have been using these for years. They are reasonably accurate (above 10W) and I can't see how it could affect the lad. i have used it with many different products including Class D amps.

 

Short the audio input on the woofer and confirm that its silent before adding the KAW. It sold be totally silent.

 

You may have a defective woofer or maybe yours does not have the class D amp. New products will need to meet the 1W max standby requirement. I think any I do will have the pre-technology standby option (an OFF switch). Otherwise meeting the requirement is a real burden.

 

[Panelhead]

The Class D amps I have seen that draw enough power at idle to heat up have issues. Usually it is the filter on the output. It rings and heats up the heat sink. These are mounted to the heat sink for this reason.

 

George

 

[wgscott]

That looks good, except I think I would need a Hall Effect one in order to measure a small current. Where I live 100 mAmp would correspond to 12.3 Watts.

 

[wgscott]

I was afraid of that. Fortunately, it is still under warranty.

 

Edit:

 

Well, it failed completely. Nothing wrong with the fuse, so I guess it is something bad.

 

[Panelhead]

The issue with the filter is normally the inductor. They; burn out, drift, or short. Then the output oscillates and heats up.

Small amps like T amps do not have this issue. Bigger ones, like a sub amp normally heat sink the inductors.

It may be a failure prone component. The bad components have broke some companies. Normally your dealer can get a replacement amplifier module. Shipping the amp to get it fixed is cheap. Shipping the sub is expensive.

 

George

 

[wgscott]

Well it is still under warranty, so hopefully they can fix it or replace it.

 

I just have to take it back to the dealer.

 

[AudGuy]

It isn't the unit mentioned, but does measure consumption and will report as Amps, Watts or Voltage. I can also teach it my cost rate and it will tell me how much I spend running a device.

 

So I tested all of the stuff that typically is on all the time, whether in standby mode, simply on or looks like it's off but is really on. Active speakers, woofers, amps, telephones, controller chargers ... on and on the list goes. After all this I concluded that I was using way too much power when everything was supposed to be off.

 

Now I use various power distribution mechanisms that I switch off when I am not actively using it, and I have been doing this for about a year now and it has even lowered my electrical energy bill.

 

My main sub-woofer in my analog system is about 3 years old, has an amp rated at 300W and is supposed to go into a low power mode when the system is turned off. When in use it draws about 100W, typical and about 35W in standby. Too much, now it gets turned off.

 

All of my equipment was like this and I would not have know any of this had I not gone to the trouble of getting a consumption measuring device and actually checking all of my equipment. Things are NOT quite what is claimed...

 

And in general, my full stack of multi-media gear draws about 500W, the fridge uses around 350W, computers are anywhere from 65W to 225W, and LED lights draw so little power you almost can't measure them. Throw away your CF and use LED. (dispose responsibly)

 

[blueixus]

Like AudGuy I switch much of my HiFi off at the mains when not listening.

 

I use X10 Plug in Module Mains Plugs linked to my Remote Control for this and it has been working perfectly for the last 3 years.

 

I have actually halved my electricity bill over the last three years which I am very pleased about.

 

The absolute worst thing I found in my system was a Russ Andrews Mains PurifierBlock which is meant to clean up the mains, it was drawing 60W! It went immediately. When I spoke to Russ Andrews about it they refused to comment.