Which watts are the right watts in SS amps?

So the upshot is, if you have speakers that are a kind load to the amp, then the amp is not called for to deliver current, and will stay reasonably flat in frequency response.

But if the speakers are a load that asks the amp to deliver current at certain frequencies, and the amp can't, then what happens at those frequencies is the amp "sags" in power at those frequencies and therefore cannot stay flat in frequency response, and becomes a tone control instead.

EG: Like the blackish grey trace shows in this graph of a tube amp that can't stay flat into a easy simulated speaker load. Which is plus and minus 6db!!! very far from sounding flat, and very mush a tone control.

https://www.stereophile.com/images/1116PLPPfig01.jpg

Cheers George

   

nutty

The amp doesn’t double, as tested by Stereophile. That you believed it did, because of the ML literature.
https://forum.audiogon.com/posts/1492322

Saying this the ML's are a fine amp and have enough current to drive probably everything, just that they don't double their wattage for each halving of impedance, they come as close as I would expect, no amp can double all the way down to 2ohms.

Cheers George

@georgehifi
So the upshot is, if you have speakers that are a kind load to the amp, then the amp is not called for to deliver current, and will stay reasonably flat in frequency response.

But if the speakers are a load that asks the amp to deliver current at certain frequencies, and the amp can't, then what happens at those frequencies is the amp "sags" in power at those frequencies and therefore cannot stay flat in frequency response, and becomes a tone control instead.

Blindjim > now this particular note, I feel I understand pretty readily. Thanks.

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@nutty > The laws of physics refuse to be cheated. Long-term, you cannot deliver more power into the speaker than you can pull from the wall.

Blindjim > makes sense. Tanks much.

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@almarg

Regarding the disagreement about whether or not some solid state amps can "double down": As I see it both sides are correct, but are focusing on different things. One side appears to be focusing on **measurable** maximum power capability, and the other side appears to be focusing on **rated** maximum power capability.

Any amplifier having low output impedance can be rated to deliver twice as much power into 4 ohms as into 8 ohms, if the 8 ohm rating provides a large enough margin relative to actual capability. A reputable manufacturer will, or at least should, choose a margin that is large enough to be comfortable relative to anticipated sample-to-sample variations, reasonable variations in line voltage, etc., but at the same time is not a margin that is so large as to be misleading. And likewise when it comes to choosing the distortion percentages upon which the power ratings are based, and in defining whether the power that is being referred to can be delivered continuously or just on a short-term basis.

Blindjim > Mucho gras Al.
Would you mind clearing up this thought of your’s?
Any amplifier having low output impedance can be rated to deliver twice as much power into 4 ohms as into 8 ohms, if the 8 ohm rating provides a large enough margin relative to actual capability

Margin? Section? Area? Range? Who picks them or it? The amp maker, Yes? No>?

I’m so confused.

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Perhaps the slant I see is not as much an argument as it is which side of the coin should one stand upon when deciding to throw IMHO a ton of frog skins at any amplifier whose job it will then be, to drive some unknown, unmeasured loudspeaker!

Be steadfast on the side of measurements alone for both speaker and amp, or capriciously dash ahead towards claimed HP and the amps audible attraction?

Dunno. But I’m begining to.


The ongoing thread here however continues to be IMO about pulling the trigger on what ever amp based solely on its ability to ‘reputedly’ double HP as IMP halves, OR choose one based on a likely ‘best guess’ notion with what appears to be enough watt/HP as you adore the influence the amp presents in music playback.

And the winner is?

Only a very small portion of all amps are being measured by third party outlets, and from what can be gleaned just on this thread, some amp makers aren’t too concerned with providing verifiable data to begin with… or so it seems.

For anyone seeking an imperical or metered method for picking out the next amp, good luck.

The technical side of the coin simply can not deliver a suitable or even just verdict as to how best to choose which watt for what speaker. Especially when taste or user preffs are batteling with the bank account for the priviledge of steering the selection committee.

This whole past time should be called Audio ambiguity.


If at all possible, as monos and run them on the same phase but different ckts. To restrict them less electrically.

The only sensible thing to do, If both are the same or quite similar topology, is to weigh the two final amp choices, and buy the heavier one.

That is one measurement which can’t be hidden or misrepresented.

Mucho gras Al.
Would you mind clearing up this thought of your’s?
Any amplifier having low output impedance can be rated to deliver twice as much power into 4 ohms as into 8 ohms, if the 8 ohm rating provides a large enough margin relative to actual capability

Margin? Section? Area? Range? Who picks them or it? The amp maker, Yes? No>?

Hi Jim,

Yes, I’m referring to ratings that are claimed by the designer/manufacturer.

I’ll explain further with a hypothetical example: During the design process the designer targets a capability of 120 watts into 8 ohms and 180 watts into 4 ohms, based in part on a belief that he can accomplish that with a design that will fall into a price range he wants to compete in. When he tests his initial prototype of the design he finds that it can meet but not significantly exceed those numbers, on a continuous basis (as opposed to just being able to meet them for say a few minutes without self-protection mechanisms being triggered), with reasonably low distortion, when supplied with an AC input of 120.0 volts.

He will then presumably want to allow some margin in his published numbers, relative to those numbers, to account for sample-to-sample differences that may occur in production, and to take into account reasonable differences that can be expected in line voltage, ambient temperature, and other variables. So let’s say that he decides to introduce a margin of approximately 16% (about one sixth) into each of the published specs, resulting in published ratings of 100 watts into 8 ohms and 150 watts into 4 ohms.

However **some** designers in that situation may instead choose to publish ratings of 75 watts into 8 ohms and 150 watts into 4 ohms, which as George has pointed out may help sell amplifiers because it can lead potential customers to consider the amp as being able to "double down." While from a marketing standpoint the downside of that kind of "specmanship" would be mitigated in the minds of many potential customers by the fact that 75 watts is only 1.25 db less than 100 watts!

The only sensible thing to do, If both are the same or quite similar topology, is to weigh the two final amp choices, and buy the heavier one.

Weight is actually a criterion that can indeed be helpful to take into account in choosing an amplifier, IMO, as there does tend to be a correlation between weight and quality (albeit a loose correlation of course), among amplifiers having similar topologies and that provide roughly similar power capabilities. Unfortunately, though, weight also tends to be significantly correlated with price, given those similarities.

Best regards,
-- Al

However **some** designers in that situation may instead choose to publish ratings of 75 watts into 8 ohms and 150 watts into 4 ohms, which as George has pointed out may help sell amplifiers because it can lead potential customers to consider the amp as being able to "double down."

Al, the big boys nearly all do it, just look at their own spec sheet proper-gander, and then compare it to actual test performed by independent testers.

I’ve PM’ed you a really good audio test sight, far more in-depth testing than Stereophile’s testing. You'll be able to view 2003/4 testing but have to join to view later ones 

Cheers George