For the past six years I have been enjoying my system which had been based around 2 Classe amplifiers which are rated IF on stereo mode as 400 watts/channel: the classe 401. Now I have them connected on mono mode each powering one speaker and I seem to have naively believed this implies a power output of 800watts/channel. Indeed the set up, powering sonus faber amatis sounds on a different level to the single amplifier on stereo mode.

However, today going over the prospectus by chance I came up with figures that show that for some reason when used in mono mode the amplifier has an output of 1600 watts per channel rather than my naive assumption of twice the stereo output.

Would this be correct? And what is the engineering/math behind it? It seems like we multiply by 2squared rather than by two to get from stereo to mono output, is this so and why?

Let's pretend your speakers have an 8 ohm nominal impedance. So when you power two speakers off one amp, one speaker per channel, each channel "sees" a nominal impedance of 8 ohms. I'm assuming your amp specs say 400 watts/channel at 8 ohms. So that's 400 watts per speaker.

Now lets bridge one amp to power one speaker. Now both channels are working together to power one 8 ohm nominal speaker. So, each channel of the amp "sees" a nominal 4 ohm load. I am going to make another assumption and say your amp specs say it puts out 800 watts/channel at 4 ohms. If this is correct, each channel has the capability to produce 800 watts when seeing a 4 ohm load. So two channels * 800 watts = 1600 watts.

So to answer your question: No. You do not have 1600 watts per channel. You have 800 watts per channel because you halved the impedance. 1600 watts per speaker, because each speaker is driven by 2 channels.

Remember that your amp isn't pumping out that much power all the time. It is just the maximum that it can do with a certain amount of distortion or without blowing a fuse or another safety device (depends on how the manufacturer rated it)

This may help you out (look for the amp bridging stuff):

www.bcae1.com

thanks , this seems to answer the poitn very clearly.
I am copying below the precise text from the classe website of the amplifer's spec:

Rated output power: 8 Ohm load 400 W (1600 W)
Stereo (mono) 4 Ohm load 800 W (2400 W)

The way it is written does appear to imply that there is a 1600w power output at 8ohm but I see how one can misunderstand this = its 8 OHm speakers ONLY if ASSUMING stereo, mono the follows as 1600 but of course that is due to implied resistance halving as the 4Ohm figure below shows>

Oh well, that explains the mystery, I suspect.

Short answer, without even reading the details of your post: NO.

thanks , this seems to answer the poitn very clearly.
I am copying below the precise text from the classe website of the amplifer's spec:

Rated output power: 8 Ohm load 400 W (1600 W)
Stereo (mono) 4 Ohm load 800 W (2400 W)

The way it is written does appear to imply that there is a 1600w power output at 8ohm but I see how one can misunderstand this = its 8 OHm speakers ONLY if ASSUMING stereo, mono the follows as 1600 but of course that is due to implied resistance halving as the 4Ohm figure below shows>

Oh well, that explains the mystery, I suspect.

Well not quite.

Using Ohm's law, 400W into an 8 Ohm load requires an output voltage of 56.6V (Power = voltage squared/resistance).

In stereo mode each channel delivers 56.6V across the load. In bridged mode the signal voltage is inverted in one channel, the speaker is connected across the positive terminals of each channel and the output voltage is now from +56.6V on one channel to -56.6V on the other for a total voltage of 113.2V.

With a 113.2V at the output across an 8 Ohm load we get 1600W or four times the power in normal unbridged mode

In practice many amps cannot deliver the required current; the ability to do so is a sign of a well designed amplifier.

Whatever you have now, you need more. :o

Short answer, without even reading the details of your post: NO.

How do you figure?
I and others say yes, with the caveat that "per channel" really means per speaker.

How do you figure?
I and others say yes, with the caveat that "per channel" really means per speaker.

Both trekguy and Chris are probably correct.

Trekguy did the math correctly for calculating power. But he calculated using voltage and resistance. Power also is calculated as P=IE. So for 1600 watts, the amount of current required would be 14 amps. For normal operation, 400 watts would require 7 amps.

Trekguy said in his analysis that "In practice many amps cannot deliver the required current; the ability to do so is a sign of a well designed amplifier." So in order to fully answer the question, the power supply would have to be analyzed to determine its ability to supply the required amperage to reach 1600 watts in bridged mode. Can the amps in question do it? I don't know but I would guess "not quite." :D

How do you figure?
I and others say yes, with the caveat that "per channel" really means per speaker.

You're not pulling that much from the wall or you'd trip the breakers. And you're certainly not pulling that much from the wall unless you're wearing earplugs at a minimum, or you have even more problems to contend with than causing a fire by drawing that much current....

If he's even asking such a question, and doesn't own a sports stadium or something like that, then you can rest pretty assured that you're not drawing anywhere NEAR that kind of power...

You're not pulling that much from the wall or you'd trip the breakers. And you're certainly not pulling that much from the wall unless you're wearing earplugs at a minimum, or you have even more problems to contend with than causing a fire by drawing that much current....

If he's even asking such a question, and doesn't own a sports stadium or something like that, then you can rest pretty assured that you're not drawing anywhere NEAR that kind of power...

You are correct of course, as you so often are sir. But I think there is a bit of apples and oranges here.

It is true that the maximum power available from a 15A household circuit is about 1800W and as no amp is 100% efficient a claim of 1600W is dubious. The specs for the 401 show 360 W consumption at idle; it might not be correct to do so but let's assume that much loss at full output. So 1600W + 360W = 1960W and that is doable with a 20A supply.

But unless we listen to test tones or pink noise or just woofers (or live in a stadium) it is unlikely that the amp will have to deliver full output for other than brief periods. Breakers won't trip and the amp's capacitors carry the load.

Moreover I think we have a constitutional right to go deaf from high sound levels--at least it sure seems that way

[quote]So 1600W + 360W = 1960W and that is doable with a 20A supply. p.quote]

Times 7 channels!?

[quote]So 1600W + 360W = 1960W and that is doable with a 20A supply. p.quote]

Times 7 channels!?


Well he only mentions two amps;).

The only circuits I have in my house for that are the two 20A kitchen circuits, but hey we all need tunes when we cook.

But really, the chance of actually drawing the full rated power for more than milliseconds is remote. I would bet that he could run them both from a single circuit at ear damaging levels and not trip the breaker (often).

And now back to serious concerns; whether to use a semi-transparent or opaque stain on the fence?

No, not times 7, he has two Classé amps.
http://www.classeaudio.com/discontinued/specs/ca401.htm

I believe 1600W brigded.