High current amplifiers?

[whazzup]

It's not the same as considering the rated power output of amplifiers? Does that impact the choice of speakers?

 

[March Audio]

Its a somewhat misleading video. The point they completely avoided is that the amount of current required is dependant upon your speakers and their impedance.

A speaker that has high impedance will not require the level of current a low impedance speaker will.

 

[whazzup]

Thanks!
When I see an amp rated for say, 200W per channel at 8ohms (on paper), is it reasonable to say that it should drive 'consumer-facing' speakers at adequate, sane, home use levels? Or if really faced with high impedance speakers, is power output still a reliable spec to base buying decisions on? Haven't really thought about checking out the maximum current of an amp, so curious to see how it fits into the understanding of published specifications.

 

[Fluffy]

Current is directly related to power, these are not independent specs. A 200W amp that drives 8ohm speakers will pump 5 ampere at full amplitude. Here are the basic formulas:

 

[whazzup]

Maybe the question I should be asking is:
Assuming high impedance speakers and 2 amplifiers with the same power rating, is it possible for 1 'high current' amplifier to drive the speakers and make it 'sound better' (sorry, I know it's a can of worms...) when set to the same volume in a room, compared to the other amplifer?

Or for all intents and purposes, 'high current' is just another marketing term to differentiate products?

I know it sounds like a stupid question, but just want to be sure....

 

[March Audio]

If the load is only drawing current that is within the capabilities of the amp then no, having more current available wont in itself make it sound better.

To say its just marketing is not strictly true however, but as mentioned it does depend on the speakers. Some have quite pathological dips in their impedance at certain frequencies and these will require more current than a speaker with a benign impedance plot. Some also have a low sensitivity which require more power (and therefore current) to reach the same volume as another one with high sensitivity.

So you cant just generalise, its far more complex.

 

[Fluffy]

Maybe the question I should be asking is:
Assuming high impedance speakers and 2 amplifiers with the same power rating, is it possible for 1 'high current' amplifier to drive the speakers and make it 'sound better' (sorry, I know it's a can of worms...) when set to the same volume in a room, compared to the other amplifer?

Or for all intents and purposes, 'high current' is just another marketing term to differentiate products?

I know it sounds like a stupid question, but just want to be sure....

There can't be an amp that has the same power rating but more current. More power=more current, they are directly proportional.

 

[whazzup]

If the load is only drawing current that is within the capabilities of the amp then no, having more current available wont in itself make it sound better.

To say its just marketing is not strictly true however, but as mentioned it does depend on the speakers. Some have quite pathological dips in their impedance at certain frequencies and these will require more current than a speaker with a benign impedance plot. Some also have a low sensitivity which require more power (and therefore current) to reach the same volume as another one with high sensitivity.

So you cant just generalise, its far more complex.

There can't be an amp that has the same power rating but more current. More power=more current, they are directly proportional.

Right, my point is a non technical user will just need to consider the output wattage of an amplifier (assuming published specs are reliable of course), for example a 500W per channel amp, and be assured that his bases are covered, without the need to consider 'high current' amps, because as Fluffy said, power and current are directly proportional.

 

[March Audio]

Right, my point is a non technical user will just need to consider the output wattage of an amplifier (assuming published specs are reliable of course), for example a 500W per channel amp, and be assured that his bases are covered, without the need to consider 'high current' amps, because as Fluffy said, power and current are directly proportional.

Its not that simple because speakers are not a constant impedance.

For example this is a random example I copied from Stereophile. Its rated at a nominal 8 ohms yet as you can see at 100 Hz it dips as low as 2.2 ohms.

At 1kHz the impedance is about 8 ohms. So what effect does this have on current?

Assuming it has a flat frequency response (we will ignore phase angle for simplicity). Lets drive the speaker at 2.83 volts ( 1 watt into 8 ohms).

the current required at 1kHz is 2.83/8 =0.35 amps. However at 100Hz 2.83/2.2 = 1.29 amps.

 

[whazzup]

Its not that simple because speakers are not a constant impedance.

For example this is a random example I copied from Stereophile. Its rated at a nominal 8 ohms yet as you can see at 100 Hz it dips as low as 2.2 ohms.

View attachment 64597

At 1kHz the impedance is about 8 ohms. So what effect does this have on current?

Assuming it has a flat frequency response (we will ignore phase angle for simplicity). Lets drive the speaker at 2.83 volts ( 1 watt into 8 ohms).

the current required at 1kHz is 2.83/8 =0.35 amps. However at 100Hz 2.83/2.2 = 1.29 amps.

But a typical consumer may not be able to obtain impedance graphs of specific speakers.
Given your example, as long as the power wattage 'covers' the max ~1.3A needed to drive the speakers across all frequencies (at a sane SPL), that's a perfectly adequate amplifier to get, right?

I understand the max current is not something normally published in amplifier specs, so just want to make sure it's not needed (given we already have power)

Or does that mean the important metric all amp manufacturers should publish, and we should refer to, are the power wattage specs at lower impedances?

 

[March Audio]

Indeed, the full information you require to make a decision regarding this may not be available. Im afraid you are looking for an answer I cant give because, it depends

It also depends on the speaker sensitivity. An 85dB/2.83V/M speaker needs twice the power to reach the same volume as a 88dB/2.83V/M speaker.

It also depends on just how loud you want it to be in your size of room and listening distance.

 

[Wombat]

FWIW

http://www.enjoythemusic.com/magazine/manufacture/0708/

 

[whazzup]

Indeed, the full information you require to make a decision regarding this may not be available. Im afraid you are looking for an answer I cant give because, it depends

It also depends on the speaker sensitivity. An 85dB/2.83V/M speaker needs twice the power to reach the same volume as a 88dB/2.83V/M speaker.

It also depends on just how loud you want it to be in your size of room and listening distance.

No worries, always keen to learn and uncover the mysteries of the published specifications....

 

[whazzup]

FWIW

http://www.enjoythemusic.com/magazine/manufacture/0708/

Oh, thanks for the link!

 

[RayDunzl]

Right, my point is a non technical user will just need to consider the output wattage of an amplifier (assuming published specs are reliable of course), for example a 500W per channel amp, and be assured that his bases are covered, without the need to consider 'high current' amps, because as Fluffy said, power and current are directly proportional.

Relationship of Amplifier output volts, current demand of the speaker, power consumed by the speaker, at an increasing SPL level.

All things being equal, of course, and using a simple ohms law calculation for an 88dB sensitive speaker rated 8 ohms.

Note that the "watts" rises quickly as you get loud.

The vertical scale applies to all 4 charted values, the bottom scale references SPL.

http://www.sengpielaudio.com/calculator-ohm.htm

 

[whazzup]

Relationship of Amplifier output volts, current demand of the speaker, power consumed by the speaker, at an increasing SPL level.

All things being equal, of course, and using a simple ohms law calculation for an 88dB sensitive speaker rated 8 ohms.

Note that the "watts" rises quickly as you get loud.

View attachment 64604 View attachment 64602

The vertical scale applies to all 4 charted values, the bottom scale references SPL.

Nicccceeeeeee, simple but really drives home the relationship. Next time I'm dieting, just going to shout at my brother at 124db.

 

[Wombat]

FWIW2

https://www.audioholics.com/audio-a...or-switch-1/amplifier-and-power-supply-basics

 

[boXem]

There can't be an amp that has the same power rating but more current. More power=more current, they are directly proportional.

Depends the load.

Hypex NC1200 OEM :
8 ohms 400 W
4 ohms 700 W
2 ohms 1200 W

Hypex NC500 OEM:
8 ohms 400 W
4 ohms 700 W
2 ohms 550 W

Both work with 84V rails, limiting their power at 8 and 4 ohms, but have different current capabilities (38 vs 26 A) limiting their power at 2 ohms.

 

[whazzup]

Depends the load.

Hypex NC1200 OEM :
8 ohms 400 W
4 ohms 700 W
2 ohms 1200 W

Hypex NC500 OEM:
8 ohms 400 W
4 ohms 700 W
2 ohms 550 W

Both work with 84V rails, limiting their power at 8 and 4 ohms, but have different current capabilities (38 vs 26 A) limiting their power at 2 ohms.

Oh! This is an interesting comparison, similar current / power at 4 and 8 ohms, but different at 2.

 

[Fluffy]

Depends the load.

Hypex NC1200 OEM :
8 ohms 400 W
4 ohms 700 W
2 ohms 1200 W

Hypex NC500 OEM:
8 ohms 400 W
4 ohms 700 W
2 ohms 550 W

Both work with 84V rails, limiting their power at 8 and 4 ohms, but have different current capabilities (38 vs 26 A) limiting their power at 2 ohms.

Those two amplifiers do not have the same power rating. The current capabilities are reflected in the power spec. That's what I meant – limited current is translated to limited power and vice versa.

But yes, load is part of the story, and also voltage. They all contribute, and that's why you can define an amp based solely on a single electrical spec. Though if you know the power delivery at different loads, you don't really need to know the current capability.