Are all watts equal?

[MikeSp]

In perusing various high end class A tube amps, I noticed that many or most of them put out less than 100 watts with some of the best only putting out 50-60 watts.

How can such small wattage drive large speakers -- even the efficient KHorns (it just doesn't seem like such amps would have much headroom)

Kindly educate me here on low watt class A amps and the speakers that they drive...

Thanks,

MikeSp

[-E-]

Remember, 1 W is still 1 W, in a sense of electricity. The sensitivity of a speaker has more to do with how loud it will drive at said 1 W.

Considering most listening is done <5WPC (unless MasterLu), a 50W Class A amp should have plenty of grip on... well... any speaker.

[MikeSp]

Originally Posted by Vesuvius

Remember, 1 W is still 1 W, in a sense of electricity. The sensitivity of a speaker has more to do with how loud it will drive at said 1 W.

Considering most listening is done <5WPC (unless MasterLu), a 50W Class A amp should have plenty of grip on... well... any speaker.

I realize that all watts are created equal in the sense of Ohm's Law, but also remember a McIntosh demo in which a MC402 was easily driven into protection mode by a CD with a drum solo with a huge dynamic range (think it was Charlie Randall doing the demo to demonstrate the protection mode) and in that sense, 400+ watts was not enough. This is why I was curious about the relatively low wattage of class A amps such as the B.A.T. VK-SE150 monoblock tube amp when compared to the potent class A/B Mc Amps. Even the vaunted Lamms have low watts compared to some of the Mc Amps.

In no way am I promoting Mc amps -- just am more familiar with them and am trying to figure out the much lower wattage of most high end amps and why several of the Mc amps need 1000+ watts.

MikeSp

[PHC1]

Originally Posted by MikeSp

I realize that all watts are created equal in the sense of Ohm's Law, but also remember a McIntosh demo in which a MC402 was easily driven into protection mode by a CD with a drum solo with a huge dynamic range (think it was Charlie Randall doing the demo to demonstrate the protection mode) and in that sense, 400+ watts was not enough. This is why I was curious about the relatively low wattage of class A amps such as the B.A.T. VK-SE150 monoblock tube amp when compared to the potent class A/B Mc Amps. Even the vaunted Lamms have low watts compared to some of the Mc Amps.

In no way am I promoting Mc amps -- just am more familiar with them and am trying to figure out the much lower wattage of most high end amps and why several of the Mc amps need 1000+ watts.

MikeSp

Much has to do with speakers choice. There are plenty of guys who drive the Wilson Maxx3 and Alexandria 2s with Lamm 18w tubed mono's and couldn't be happier. Those speakers are well designed with high enough efficiency and forgiving impedance curves to allow themselves to be driven by such low tube watts.

Also keep in mind that tubes clip in a very different way than most solid state amps. The tube clipping is usually soft and results in odd order harmonic distortion which is much easier on the ears than solid state "hard" clipping which results in even order harmonics and can actually fry tweeters.

[2-Channel]

Speaking of efficient speakers and high end, low wpc, tube amplification, I found the same types of numbers when perusing the Einstein and Acapella product lines.

PHC1 ... have you done any auditioning of these more exotic equipment lines like Einstein, Acapella, etc. ?

http://www.einstein-audio.de/

[PHC1]

Originally Posted by 2-Channel

Speaking of efficient speakers and high end, low wpc, tube amplification, I found the same types of numbers when perusing the Einstein and Acapella product lines.

PHC1 ... have you done any auditioning of these more exotic equipment lines like Einstein, Acapella, etc. ?

http://www.einstein-audio.de/

JSCC (Jerry) is our resident expert on Acapella speakers since he has a pair. We had a discussion over in the Lamm forum on that. I have not personally had a chance to listen to Acapella line.

[JemHadar]

Found a good article on the Web

http://www.rocketroberts.com/techart/amp.htm

"If we had a perfect amplifier (and it was plugged into an outlet that had unlimited current capability), its output power rating would double each time the load impedance was halved. For example, let's say the amplifier puts out 200 watts per channel at 8 ohms. At 4 ohms, it would put out 400 watts per channel, at 2 ohms it would put out 800 watts per channel, and at 1 ohm it would put out 1600 watts per channel. For the perfect amplifier, one could keep going with this until the load impedance approached zero, at which time the amplifier output would approach infinity! On the other side, if the load impedance was 16 ohms, the amplifier would put out only 100 watts per channel. In this direction, one could keep raising the load impedance, and the power output would grow smaller and smaller.

The power supply of the perfect amplifier generates a DC voltage that does not change no matter how much current is demanded from it. This means that the perfect amplifier can drive an unlimited number of speakers. In the real world, amplifiers have real power supplies which do have limits as to how much current they deliver (and real world amps use output devices that are only rated for so much current before they self destruct). For such typical amplifiers, the 4 ohm power rating is usually about 50% more than the 8 ohm rating (and if a 2 ohm rating is given, this is maybe double that of the 8 ohm rating). Amplifiers with exceptional power supply designs will do better than this, but eventually a limit will be reached (if by nothing else the AC outlet can only deliver so much current!). Lesser designs will "run out of juice” when driving the heavier loads. Most decent amplifier spec sheets will specify how much power the amp can deliver into various load impedances. If an amp’s spec sheet gives a 8 and 4 ohm rating, be careful before using the amp with 2 ohm loads. It might work, but more likely it will be stressed out and may overheat or fail prematurely"

...seems like the MC2KW comes pretty close to being the perfect amp...delivering, for all intents and purposes, near infinite current and that with a rock solid DC voltage on the rails. Maybe it is brute force over finesse...but you can't argue with the laws of physics

Had the good fortune to hear them several times, it is the best amp I have heard to date...it makes reproduced sound "real"

THX

Jacques

[harry33]

Originally Posted by Jem666

Found a good article on the Web

Power Amplifier Fundamental

"If we had a perfect amplifier (and it was plugged into an outlet that had unlimited current capability), its output power rating would double each time the load impedance was halved. For example, let's say the amplifier puts out 200 watts per channel at 8 ohms. At 4 ohms, it would put out 400 watts per channel, at 2 ohms it would put out 800 watts per channel, and at 1 ohm it would put out 1600 watts per channel. For the perfect amplifier, one could keep going with this until the load impedance approached zero, at which time the amplifier output would approach infinity! On the other side, if the load impedance was 16 ohms, the amplifier would put out only 100 watts per channel. In this direction, one could keep raising the load impedance, and the power output would grow smaller and smaller.

The power supply of the perfect amplifier generates a DC voltage that does not change no matter how much current is demanded from it. This means that the perfect amplifier can drive an unlimited number of speakers. In the real world, amplifiers have real power supplies which do have limits as to how much current they deliver (and real world amps use output devices that are only rated for so much current before they self destruct). For such typical amplifiers, the 4 ohm power rating is usually about 50% more than the 8 ohm rating (and if a 2 ohm rating is given, this is maybe double that of the 8 ohm rating). Amplifiers with exceptional power supply designs will do better than this, but eventually a limit will be reached (if by nothing else the AC outlet can only deliver so much current!). Lesser designs will "run out of juice” when driving the heavier loads. Most decent amplifier spec sheets will specify how much power the amp can deliver into various load impedances. If an amp’s spec sheet gives a 8 and 4 ohm rating, be careful before using the amp with 2 ohm loads. It might work, but more likely it will be stressed out and may overheat or fail prematurely"

...seems like the MC2KW comes pretty close to being the perfect amp...delivering, for all intents and purposes, near infinite current and that with a rock solid DC voltage on the rails. Maybe it is brute force over finesse...but you can't argue with the laws of physics

Had the good fortune to hear them several times, it is the best amp I have heard to date...it makes reproduced sound "real"

THX

Jacques

Very instructive article.Thank you

Harry

[1KW]

Jerry,

[JSCC]

Originally Posted by 2uberoller

Jerry,

Hi 2uberoller, I am pretty bad at taking GOOD pictures, so managed to "borrow" some pics of the same amp to share. The setting up process is EXACTLY the same. Not an easy task too! Will share the "real" pics when I am done. Meanwhile, hope you like these.