Axiom Home Page Forums General Discussion What's New At Axiom Axiom Amplifiers: The Next Generation

Sorry, I was a little late to the party on the 20A thing. With discrepancy, I was just talking about the power. I don't know about the 4ohm thing.

I have a full electrical panel at my house, so a 20A circuit would be a bit more pricey.

There are many things to consider when looking at amp specs. The most important in my mind is the fact that a speaker is not a constant resistive load. The M80 only drops to 4ohm in certain frequency ranges Impedance graph

Amps are not asked to produce continuous high power levels, it is transient and most power is required by the woofers so if your using a sub and not powering the lower frequencies the required power is much lower. This is why sub amps are such high power .

Read the posts on page 4 and 5 of this thread by Andrew, it explains something that is really quite complicated in an easy to understand fashion that even I can wrap my mind around.

I am not sure what other questions you had other than why some amps double their power into 4 ohms. The AdA amps do up to point where the power supply can no longer maintain current to the rails. 3 channels seems to be the limit ,If they used an even larger power supply and 20A circuit they could maintain rail voltage over more channels.


Andrew Welker
The rail voltage remains constant until we reach the maximum continuous current capability of the power supply, at which time the rail voltage will reduce or "sag". This is why the power output drops at a certain point when more channels are added. At that point the maximum rail voltage is no longer the limiting factor in output power, it's now the supply current and the subsequent drop in rail voltage. If we had an unlimited supply current available, the power output would keep doubling at each halving of the load impedance until we reach the current limits of the amplifier output stage, which has current limiting protection. On the A1500 this will not take place until you're down into sub-2ohm territory.

Richard

Thanks to all of you guys for all the great input and help.

Im still saving for my subwoofer. After that, it will be a 3 channel ada1500. Im set on it now from there...we will see. Hopefully ill stop there lol :p

No thank you. This helped me at the same time. Hopefully my rambling made some sort of sense. I am totally sure many others like JohnK or Dakkon could have got to the point a lot quicker than I.

HA HA on a side note, its all I can do to not spank my credit card and alleviate my new yearning for a 5ch ada 1500.

Richard

Spank it!

I says pardon me LOL

If you want to evaluate the validity of continuous amplifier power output claims, all that's required is some simple math.
In North America, with a typical 15A AC circuit at 120V, you can draw a maximum of 1800 watts. For a 20A circuit you can draw a maximum of 2400 watts. Now that's simply what you can get out of the wall, not what you can get to your speakers, because no amplifier+power supply can be 100% efficient. Class AB amplifiers with linear power supplies typically range from 50-65% and Class D amplifiers can range from 80-95%. So, for a 5-channel Class AB amplifier with 50% efficiency to continuously supply 600 watts to all channels would require 6000 watts from your household AC, not to mention having to dissipate an enormous amount of heat...

Andrew, my takeaway from this is that Emotiva's claims are baseless. Something else that came to mind for me is the fact that , typically one room is on a single breaker. So not only am I feeding my amp , I am powering a 60" plasma , my receiver , my dvr or bluray player etc which doesn't even allow my amp access to that 1800 watts. I have a killawatt meter and my tv takes 300 on its own.

Richard

This is a very good point but remember, it is virtually impossible with any music or movie programme material to actually require full output for all amplifier channels at the same instant in time. Also remember that your the impedance of your loudspeaker varies with frequency. When we publish a continuous power rating it will always be with a 1kHz sine wave driving a purely resistive 8 or 4 ohm load. These kinds of bench test conditions are nice for defining an apples to apples baseline for power output, but they represent the kind of worst-case scenario that will likely never be seen in the context of an actual system.

Thanks for clarifying that Andrew, I tend to get ahead of myself when I am typing and leave things out. I realize music is transient and speakers are a constantly changing load (impedance). It is much the same with cars, dyno tests are a good measuring stick for comparison, but no one put's there car up against a building and floors it . Amplifier rating (and horsepower) are some of the most over exaggerated specs. We as humans love MORE, and it is an easy way for marketers to get our attention without being clear about what we are buying. I look forward to purchasing an ADA amp and the fact that they are efficient makes it all the more desirable.

I read through this thread and managed to get all the info I needed, but what would be great is if all this info was in one place as a sticky or maybe something in your blog.

Richard