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Home power usage of Class D, different wattage amps?

marcray

marcray

Nov 28, 2006
1,415
63
Englishman in Oyster Bay, NY
Disclosures
Aging Former Bass Player
#1
Here's a silly question... for reasons only I need to know I'm considering a 500 watt or 250 watt class D amp. However, a lot of my use will be home practice probably with headphones, so, does a 500 watt amp use more (or a lot more) power when using headphones?

I know it sounds silly, if most of my use is home in headphones just get the smaller amp, but I'd like to know I can leave the house and use it for a reasonable size gig or rehearsal... flexibility and portability.
 
#2
marcray said:
Here's a silly question... for reasons only I need to know I'm considering a 500 watt or 250 watt class D amp. However, a lot of my use will be home practice probably with headphones, so, does a 500 watt amp use more (or a lot more) power when using headphones?

I know it sounds silly, if most of my use is home in headphones just get the smaller amp, but I'd like to know I can leave the house and use it for a reasonable size gig or rehearsal... flexibility and portability.
Click to expand...
Hopefully your amplifier has a headphone output and you're not plugging your headphones into the speaker output. That being said, the headphone output has it's own small stereo headphone amplifier separate from the power amplifier section that powers the speaker/s
 
#3
Scottkarch said:
Hopefully your amplifier has a headphone output and you're not plugging your headphones into the speaker output. That being said, the headphone output has it's own small stereo headphone amplifier separate from the power amplifier section that powers the speaker/s
Click to expand...

well, yes, the amps I'm considering have headphone outputs. So you're saying that no, it makes no difference when monitoring through headphones.
 
#5
Amps use power to make power.
Aside a small 'overhead' current for stuff like the preamp section and some lights, amps consume power only in proportion to their output.
So if you're not using power to move a speaker, you're only running the pilot light. A kilowatt amp isn't consuming 1000W unless it's cranked.
More like 1W...
 
#6
It's an interesting question,
It's nothing to loose sleep over, but if you were to use a lower power amp, you'd have less draw at lower power levels.

for example, look at an efficiency chart for a class-d amp
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This is a medium powered amp an at 80w it's twice as efficient as class-ab. But way over on the left, at the milliwatt range, It's too small to see but things are likely more equal. Both amps need lots of capacitors charged to be ready to respond to higher power when it called for.

To get that class-D line even farther left even more vertical you'd need a power supply to only supply low watts, when low power is needed. I don't see too many heads that have a power-amp off mode, but keep the headphone available.

The point here is headphones are down in the Milli-watt range. If you want to use milliwatts at the highest efficiency you should use an amp designed for low wattage. It can be a class-d amp as most cell phones, TVs and other low wattage amplifiers these days are class-d. For that very reason. Low power draw, low heat, long battery life. The power supply in this case is designed for low power.

I do expect to see class-d with even more featured power supplies that essentially go into low power mode when they're not needed. It's one of the areas class-d could grow in.

A 500w amp will also probably have a fan that draws some current at low volume levels.
 
#7
seamonkey said:
A 500w amp will also probably have a fan that draws some current at low volume levels.
Click to expand...
This is especially true if the amp has a tube preamp (hybrid).
To minimize idle power consumption, an "all solid-state" will probably draw a few (tens of) mW less.
For example - my MarkBass compressor wants about an amp of 12V and it doesn't really amplify anything - but it has to run the heater...
 
#9
The difference between a 250 and 500 watt model of the same topology at "idle" (that's what a headphone load represents) will be 5 or 6 watts.

Some products do use the power amp as part of the headphone drive circuitry. The reason is because some amps use sophisticated dynamics management along with the power amp, and this is then captured by using the power amp as a headphone driver.
 
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#11
I don't think it'll make much difference for you at all if your primarily going to use headphones because your talking a headphone out and not the main power amp. Some amps aren't happy not having a load so be aware of that.

For others looking at class d amps specifically. I would like to mention class D while efficient and quiet can have specs that are greatly exaggerated. They might say its a 1000w amp when it's only 500w and so on. Warwick specifically pointed this out when they released thier 1000w class d head at namm a couple years back. But I'm not just taking thier word for it. I've experienced it. I have a class d crown XLS 1500 power amp and a old swr750 power amp. The 750 while rated at basically half the crown is actually the more powerful amp. Still i use the crown these days because its powerful enough, is dead silent (no unwanted noise), and it weighs like 10 lbs. but just wanted to put this out there because if i had decided to save a little and went with the XLS 1000 i probably would've wanted more power which would mean selling the 1000 and upgrading to something bigger.
 

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