Amplifiers for B&W 801 D4s

[FreddieFerric]

Originally Posted by Charles

...The rule is 10% for solid state amps (the D'AGostino rule) so with a 1.25KW you have 125 superb watts and a headroom of 1000 watts for peaks. So the 1.25KW is your amplifier of choice, if you really want to upgrade.

Now as to the 3500's. They are better amps than the 1.25KW's but they are also less reliable. They drive my XVX easily off the 4 ohm taps so for your 801's, they will do a superb job off the 8 ohm tap. In fact I would say that they would be absolutely perfect for your speakers. The 10% rule does not apply to them and you will have 400-500 watts available to you.
Best

Charles

Hello Charles. Care to expound upon this "10% Rule?" I've searched hi and lo through google and come up empty.

[Charles]

Originally Posted by FreddieFerric

Hello Charles. Care to expound upon this "10% Rule?" I've searched hi and lo through google and come up empty.

It's from years ago when I used to own Krell. You're not going to find it written down anywhere. The old Krells that were made by Mr. D'AGostino had huge power supplies. My FPB 700 had a 6K watt power supply. The Krell dogma when Mr. D'Agostino owned Krell was the bigger the power supply and the larger the amp the better it sounded. Solid state amps need to loaf along to sound their best. This is not true of tube amps, which is why you hear that a tube watt is worth about 10 solid state watts. As a solid state amp becomes stressed, it can begin to sound hard. For example, when I was running my 1.25KW's with my XVX I could require 250-300 watts on live performances in my relatively small room. It was loud but you want a live performance to sound loud.

An XVX really needs a Krell Relentless or a MC2.1KW to do it justice. A 1.25KW cannot do it full justice. The XVX is a super speaker, maybe the best in the world which is why I bought it. The I.25KW is a very fine solid state amp but let's be honest, it's not remotely in the same league with my XVX, but neither is a Momentum or anything other than a top line Boulder, Burmester, Constellation, etc. costing hundreds of thousands of dollars. No, ufguy 73 needs a 1.25KW for his B&W's if he really likes to play them loud sometimes. It's an excellent amp; perfect for his speakers. Because you don't have to pay for engineering already expensed out, it is the equivalent of about a 40K solid state amp by other manufacturers. That's why Mac is such a good buy, IMO.

This is precisely the reason that folks with 452's or 611's opine that their speaker rated at 4 ohms sounds better off the 8 ohm tap. The amp will definitely supply more watts with the impedance mismatch but the price you pay is a hotter running overstressed amp.

I really liked the way my XVX sounded with my 1.25's. They sounded great. The XVX is an incredible speaker in that it is absolute reference quality but very forgiving and musical. I think it would sound good (within reason) with almost any amp. But I am under no illusion that they could match something like a Relentless matched to my XVX. On the other hand, my 3500's do a much better job. I wouldn't swap them for anything on the market. It really is a great/unique tube amp. Mac has the best tube circuit and the amp puts out 200-300 tube watts with the Mac tube sound that I remember as a kid. In my room it drives my XVX superbly, but in a larger room, you need the 2.1KW or a Relentless, etc. The new 2.1KW is the amp to match with my XVX in a large room. The XVX has no upper dynamic limit.

Best

Charles

Of course, these are just my opinions

[FreddieFerric]

^^Thanks for the reply Charles. I don't mean to derail the OP's thread, so I'll leave it with this understanding. What you're suggesting is that a solid state amp is at its best when it's only using up to about 10% of its rated power output. After that sound quality begins to degrade, so reasonably speaking the remaining 90% exists to handle the large dynamic swings that certain types of music may contain.

I understand a vacuum tube is a different animal with very different distortion characteristics, which may explain why my 1502 sounds so much better than my MA8000.

[Charles]

Originally Posted by FreddieFerric

^^Thanks for the reply Charles. I don't mean to derail the OP's thread, so I'll leave it with this understanding. What you're suggesting is that a solid state amp is at its best when it's only using up to about 10% of its rated power output. After that sound quality begins to degrade, so reasonably speaking the remaining 90% exists to handle the large dynamic swings that certain types of music may contain.

I understand a vacuum tube is a different animal with very different distortion characteristics, which may explain why my 1502 sounds so much better than my MA8000.

Fred, you haven't derailed the thread. And yes, that's absolutely correct. The March 2024 Stereophile reviews the Krell KMA-i800 mono power amp. Here's a quote (Dave Gordon speaking) from the review taken from p.73: "No one is going to use this much power, but it makes average listening levels, which may go up to 100 watts, sound much better, because as you approach the limit, your distortion goes up dramatically..." He goes to elaborate quite eloquently and it is exactly the D'Agostino 10% rule that I just stated. So here it is in print on p.73 March Stereophile under "Goals and Values" if anyone cares to read. I happen to agree with his view and also Mr. D'Agostino's from years ago.

Extremely large solid state amps are ideal for folks like me and ufguy who have large speakers that can play loud and soak up a lot of watts. These amps are excellent but a pair will set you back 73K. I think the 1.25KW is totally competitive with them at a cost of 27K. The KMA-i800 if you read the review has a lot of new engineering developed exclusively for it. And you pay for it. I have no problem with that. Most manufacturers when they introduce a new flagship or a new model, always include significant new circuitry. However, the 1.25KW simply improves the design with better parts like the Thermal Trak output transistors, larger capacitors, shorter circuit paths, Solid Cinch binding posts, etc. But the basic technologies do not change. I personally think that a 1.25KW is 100% competitive with the new Krell flagship at 36% of the price. I personally would prefer the 1.25KW. It will be in production long after the KMA-i800 has been discontinued and will outsell it probably 20 to 1. It weighs more than the Krell and produces as many watts. You must decide whether you like the Mac or Krell sound better. For me it's a no brainer. I have never said that Mac sounds the best but that the Mac sound is competitive with anyone's. I have just purchased a MC2.1KW. I received an excellent trade in for my three 1.25KW's. Why? because they are still in production and will be for many years to come. This will not be the same for the KMA-i800. It was not over a mere four years before the Dag Relentless was "improved" to the Epic for a cool 349K for a pair. If you have an unlimited budget just send your Relentless back for the upgrade costing thousands of dollars on top of the hundreds of thousands you have spent on the original purchase. I prefer the 2.1KW for 50K that will remain unchanged in production for the next 15 years. The wattage and weight and all specs for the two amps are comparable. I waited patiently for many years to buy this Mac amp

Best

Charles

p.s. I am using the Relentless as an example because I think Mr. D'Agostino is possibly the greatest of all the audio engineers. The same could be said for a Boulder, Burmester, Constellation, etc. flagship. They cost hundreds of thousands of dollars for a pair and will not remain in production unchanged over 5-7 years.