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Kw hours - 'green' concern?

Arranger

Arranger

Mar 9, 2003
490
3
Pennsylvania
www.soundclick.com
#1
I'm curious if an amp expert here can tell me how much relative power my amp uses in various situations.

I have a QSC PLX2-1804. When I'm practicing quietly in a household situation, am I drawing maybe just a few watts, perhaps equal to plugging in a small wattage light bulb? Do I have to open it up loud to begin drawing power equivalent to a few 100w spotlights? I'm sure amperage comes into play here somewhere, but I'm curious to know how my electric meter is affected.

Sometimes I wonder if I'm consuming energy excessively when I use a powerful rig in a situation where a practice amp would do.
 
#2
That's an interesting question.
I've seen efficiency curves
Link Removed

Your amp is class-ab
You'll see that the onset of the curve is very steep for the first 1-2% - this is where the amp is most inefficient. But over all it's linear - reaching around 50% at it's maximum power. So a lower power class-ab being ran at it's upper power limits is going to be more efficient than a high power amp running at low output. The bigger amp also you'd expect to have bigger supply caps and need to charge those.

You'll see class-d is overall more efficient - all around.
If your practice amp is class-d - then for sure you'll save power. Especially if the power supply has power factor correction (PFC)
 
#5
This is a great question, surprised I don't see more discussions of this nature on TB. Perhaps Bob Lee of QSC will give us some info on your question.

And on a related note, I've got a Crown Macro Reference amp from around 1990 that's always dimmed the lights of my house when it turns on. Killer sounding amp, it's in my stereo rig right now, but I got a hunch it's a power hog, gulp.
 
#6
rpsands said:
Are you sure the PLX is class AB? I thought it was something different and weird, like G or H something?
Click to expand...

You're right. It's "2-Tier Class H" from page 2 of the product specs sheet at: Link Removed

The Thunderfunk is a "fast switching amp" but undefined in any literature I can gather. I take that to likely mean an A-B, but I'm not really sure. A little help would be welcome.

My main reason for this thread is to determine how much electricity I'm really chewing through in the various situations that I play.
 
#7
Most of the 2 and 3 level G or H amps are actually rather close to the class-D efficiencies. That IS the point of all that extra stuff, after all.

Efficiency is NOT everything, though.

Most power amps draw from 50 to 150W at idle. Multi-level draw less, huge class-AB draw the most.

AFTER that "base power draw", the power is dependent on signal level. Yes the efficiency affects it, but if you play softly you use less power even with a big amp.

The big amp may use more power at idle, though. A class-D generally uses nearly nothing at idle, and adds only a few percent over the actual speaker power at any level.

However, with a multi-level type class G or H amp, the difference between it and a class-D is smaller, and consists largely of the difference of idle power draw between them.

A tube amp is another thing entirely, often drawing half of its ultimate power at idle....

Looking at the spec sheet you referenced, find the "power requirement" line, which is spec'd at 1/8 power with pink noise. That is a standard spec, and if you compare that line in different amp spec sheets, you will get a decent indication of the efficiency relationships between them. It isn't a perfect comparison, and not all units give that info, but its a reasonable indicator.
 
#8
Jerrold Tiers said:
Most of the 2 and 3 level G or H amps are actually rather close to the class-D efficiencies.
Click to expand...

Not so sure. Even QSC switches from class-h to class-d for their big guns
[Invalid or Expired Link Removed]

And every chart I've seen has class-h a moderately higher than class-ab, but nothing near the 90% to 95% you see from modern class-d
Link Removed

I don't see consumer equipment heading towards class-h but I see lots of class-d. Class-h days look to be numbered
 
#9
Fa-gid-a-bot-it!

If you have an electric stove, electric dryer, or central air conditioner....THOSE are THE THIRSTY ONES.

I practice at home via a QSC2402 into an ACME B2 at low volume, no concerns. Also, ALL of my lightbulbs are CFL's not incandescent(been doing that since CFL's came out). If you are worried about it too much, get a POD or something similar and some headphones. Bob will clarify the VA x time(volt-amps/kWh of your QSC) but it's tiny compared to the stuff at the top. BSEE, 1989.
 
#10
seamonkey said:
Not so sure. Even QSC switches from class-h to class-d for their big guns


I don't see consumer equipment heading towards class-h but I see lots of class-d. Class-h days look to be numbered
Click to expand...

Much of that is because class-D requires so few parts, and because it scales very well, the same controller will work with a wide variety of power stages. (there are lots of details, so don't nitpick me on this one, please).

I probably should have said that the multi-stage units CAN approach class-D... they certainly don't have to. The more steps, the better they get, but the more complex they get.

Class-D relative simplicity can win out big when looking at parts count.
 
#11
You should see the meter spin while I'm cranked up... Al Gore has me on an energy watch list.... This topic is pretty funny.

The A/C is spinning all the time, I'm going to go sit in the hot tub now and fart some bubbles. Once midnight hour goes I'll open all the windows up and play a few rounds of a couple favorite Iron Butterfly tunes.

OVER
 
#16
Putting the Kill-A-Watt plug-through meter on one of my bass rigs:
QSC PLX2-1804 at idle = 33 Watts
BBE BMax Preamp at idle = 5 Watts

In comparison, here's one of the 9 computers I have running between my home and offices:
Uniterruptable Power Supply = 5 Watts
19" Flatscreen Monitor = 12 Watts
PC (a legacy single-core AMD model) = 90 Watts

My Conclusion:
Play more bass and do less computing - It's BETTER FOR THE ENVIRONMENT! :bassist:
 
#18
Off the cuff, at solo practice levels a large amp will use more energy than a small amp.

One of the common problems in "thinking green" is in only viewing part of the picture. Buying a practice amp would use less electricity at home, but what about the energy & resources to make the practice amp & to ship it to you?
 
#19
JustDavid said:
Off the cuff, at solo practice levels a large amp will use more energy than a small amp.

One of the common problems in "thinking green" is in only viewing part of the picture. Buying a practice amp would use less electricity at home, but what about the energy & resources to make the practice amp & to ship it to you?
Click to expand...

^^^ Good point.

I've gotten into these discussions w/ co-workers talking about them buying a new efficient car versus me keeping my old truck on the road (Dodge Dakota, 354,000 plus miles).

Sure, they get more MPG, but there is a large amount of energy and resources spent manufacturing and transporting that car (usually an import) that rarely gets talked about.

Anway, a good thread on a timely topic.


PS.... I practice 99% of the time on my ABG as well. :bassist:
 

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