"High Current"

Sean...This issue of measuring power "at" clipping is new to me. I usually see specs quoted at some specified level of distortion (presumably an acceptable level). But isn't it true that distortion typically begins to increase abruptly just before clipping, and the manufacturer takes the power value just before this happens? I suggest that power measurements at the two points will differ only slightly.

As an aside, how do you deal with an amp that doesn't clip, because it has clip limiting. In that case I think you will just see increasing distortion as the signal peaks are rounded off.

All of this comes back to how the manufacturer wants to market the product and how the marketing department thinks will be the most effective manner at achieving those goals.

Given that i've seen amps rated at 200 wpc @ 8 ohms clip at 280 wpc, there's obviously some discrepancy and sometimes sizeable differences between ratings and reality. Given that the same amp was rated at 400 wpc @ 4 ohms and clipped at 418 wpc may shed some light on the subject.

While some might say that the manufacturer was just being "conservative" with their 8 ohm rating, others might say that the "doubling down" figure of 200 / 400 looked more impressive to the audiophile than a 250 / 400 rating. This is especially true since we are only talking about a percentage of one dB in rated power @ 8 ohms.

I think that a common question / statement in this type of situation, and one that i've seen here on Agon before is, "How much more would an extra 50 wpc get you when you've already got 200 wpc to start with?". Given the average audiophile's way of thinking, and this was already expressed in this thread above, isn't it easy to see why the manufacturer would "lie" about how powerful the amp is?

By down-grading the power rating of the amp by a "mere" 50 wpc, they can now pick up the "prestige factor" and "reputation" of building a "beast of an amp" that "doubles down". If it actually DID double down as impedance was halved at clipping, we would know for certain that it IS a beast of an amp with a very ample power supply and output stage. Seeing that it actually doesn't come close to doing that at clipping tells us that it isn't nearly as "beefy" as they want us to believe.

This is called marketing and it is pretty much what high end is all about. The more successful marketing is, the more product that they can sell and the more they can charge. The approach that i'm talking about removes the gloss of marketing and allows one to see the actual build quality of the entire product at a glance, hence the "newness" of a rating like this to you. They don't want you to know the truth about their product, they want you to be fooled by the hype. Sean
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Sean, IS it possible to manufacture an amp for home use that doubles down at clipping to, say, 2ohms??
I'm not sure, but i think it's theoretically very dificult?
Cheers

The Sunfire amps can do this with enough AC and the right internal fusing. I've got test results from an old magazine review on one of the original Sunfire's that verifies this. I'm not saying that i consider the Sunfire's to be the "best built" ( NOT by a longshot ), "built like a tank" ( they aren't ) or "the best sounding" ( no way ). What i am saying is that if Bob Carver could do this 10 years ago, i don't see any reason why others can't now. Especially "big name" amps that cost WAY more money and weigh two or three times as much.

One should bare in mind that this is NOT a "little" amp either. We are talking about a product rated at 300 wpc @ 8 & 600 wpc @ 4. For the record, this amp EASILY beat the factory ratings too, producing well over 700 wpc at clipping into 4 ohms and almost 1500 wpc into 2 ohms. I can provide the specific figures if someone is really interested, but i'll have to dig them up.

How much easier should it be to achieve similar results when starting off with a much smaller amp that needs less current, not as much of an output stage and even less heatsinking? There really is NO excuse for something like this other than cut-corner production and less than optimal design. Sean
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Sean...To achieve the "doubling down" at clipping which you describe requires a substantial increase in the power supply cost. It is not a characteristic that is particularly useful in the home audio situation, where amps are not driven to clipping. (Pro sound is a different situation). While you are technically correct, I think that the law of diminishing returns comes into play here.

Again from my military electronics experience...when I went to work in 1961 "built to mil specs" really meant "overdesigned", and the poor taxpayer paid the bill. Recently we have built even the most complex military systems (such as a Fire Control System to prepare and lauch 24 ICBM) by assembling Commercial Off The Shelf (COTS) hardware. That old custom designed stuff was interesting work for the engineers, but common sense prevails.