current versus watts

Herman: thanks for the response. then, is it fair to ask when looking at an amp what the max current is and view it as a minimum threshold. for instance, in the example above, if the amp can produce 12.24 amps at 600 watts (and also assume a really high quality amp that doubled again to 2 ohms)and 24.48 amps at 2 ohms that is fine. Is there value to "headroom" on the amount of current needed?

Dangelod

>>“Seems like all high quality amps clearly describe output in watts , with the best amps doubling output as impedance is is halved.”<<

You don’t actually think that do you?

Nearly every body is aware of the term ‘watts’ as it applies to an amps output…. Even novices & beginners, to one extent or another. Some will even say an amp is better than another due to the watts it puts out…. But such statements are quite shortsighted and very inexperienced.

“Watt” is the representation of the relationships between curren, voltage, and resistance or load.

Watts = an easier way to describe one facet of amplification usually…. It’s not the end all be all of amps however. I wish it were that simple!

From a somewhat less naive perspective, it could be said one amp is subjectively ‘better’ than another, without respect to the power output characteristics, judging by the sound of it instead…. Or by how much it sells for… Or by it’s design topology… Or merely by it’s classification, A; A/B; D; Tube; SS; Transformer coupled, truly balanced, or even it’s output devices.

However, there are other deliberations which will conclude if one amp is bested by some other… not purely by it’s numbers.

Whether or not an amplifier doubles up it’s power output as impedance is halved, is one thing…. Maybe a mechanical need or maybe not, for some, but as the sound being produced is of paramount import, how it produces power should not be the singular consideration or even a thoughtful way to categorize which amp is better than another at all.

When the specs of an amplifier gains more respect than does it’s voice… within reasonable thought to the application, inordinate frustration and suffering may ensue due to the lack of synergy any old amp will yield once set into a finely tuned existing setup, just because it’s power doubles down!

Still common ground needs be in place so all can speak ‘audio-ese’, at least a little. Amp makers start saying this one puts out 5.5 A or 85 V, and darn few will be able to apply such info as they seek the right sound/amp for their intended purposes. So they use a commonly known term more can relate to with which to somewhat better position their power products into.

It is indeed about far more than the amount of watts on tap very often. Usually it is about what kind of watts, instead.

Amps aren't rated for "max current" since that depends on the load. Most amps are voltage amplifiers; they try to hold the output voltage at a certain level for a given input and the amount of current they produce depends on the load. The 300W/8ohm amp above produces a maximum of 49V. This 49V divided by 8 ohms is 6.12 amps (Ohms law.) If the load drops to 4 ohms then it will still try to maintain the 49V so it needs to deliver 12.24A. If loaded with 2 ohms it will try to deliver 24.48A, try to deliver 49 amps into 1 ohm, and so forth. At some point any amp will be unable to deliver the required current.

All else being equal an amp that can deliver more current is preferable over one that can't, but things are never equal. Some speakers have big dips in their impedance at certain frequencies and theoretically benefit from a high current amp, or better stated benefit from an amp that can deliver high amounts of current when required to do so. So yes, this headroom is a desirable characteristic if the speakers you are using call for it but is not the sole criteria for picking an amplifier.

If you google Ohms law and speaker impedance and you can find a wealth of material about these fundamental concepts.

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Sound quality has little to do with current (otherwise the tube industry would have died decades ago) and has everything to do with distortion. That is a topic for a different thread.

'Current' is an issue about which there is a lot of mythology. see:

http://www.atma-sphere.com/papers/myth.html

"Sound quality has little to do with current"
is a half truth. It depends on the speakers impedance curve.