Sonus Faber Stradivari amp: X600.5 or X1000.5 ?


I want to know which power amp is better for my new speakers (Sonus Faber Stradivari) combined with ARC REF3. Ive just listened a few days ago the X350.5 and i loved it so much. Right now i have a pair of MC-501 but i'm a little dissapointed of them when i try to listen to some complex music like rock and others. Is X1000.5 a good choice for it or X600.5? The X1000.5 have 2000 wats in 4ohms?
Anyone listened to both of them. Let me know.

I have a X350.5 and love the sound. My friend has a set of X600.5 and a new set of XA160.5s. I would buy a set of XA160.5. Sonically the and power wise the XA160.5s are way better. I have heard a set X1000.5 and they are just OK. The X600.5s sonically sound like the X350.5 but just more powerful. The XA160.5s will be my next amplifier upgrade. The power on the XA160.5 has it where you need it and it sounds about the best I have heard. Realistic, Airy, Open Rich, Powerful, Smooth and just true to the music. I cried the day the XA160.5s left my house but my friend was kind enough to let me try them on my system while he was on vaction. Unfortunately they are a lot more money than my X350.5. Sometimes I think those guys at Pass labs have me hooked on the sound of their products. Sometimes I feel like a junky at a crack house.

A gentleman I know is using the CJ ART amplifiers with the Strads, and the sound is absolutely amazing! These are the finest tube amplifiers I have ever heard, the CJ amplifiers were able to play quite loudly in his room 30 feet long 20 wide 8 foot ceiling.

The new CJ ART amplifiers are remarkably transparent without any tube bloat and a rich midrange, and stunning dynamics.

If you are in his area, Long Island NY I am sure he would allow you to hear his system.
The Strads are very sensitive, 92 db.+ and there is therefore no reason to use a high-powered amp with them, unless you listen at extremely loud sound pressure levels, in which event it makes no sense to use Strads (while they go plenty loud, they are primarily a finesse speaker).

It never ceases to amaze me how many people do not know that the vast majority of HIGH-POWERED AMPS SOUND MEDIOCRE. Big amps almost always use global feedback in order to control the circuit, which takes the life and dimensionality out of the music, and they also use dozens of output devices (i.e., lots of transistors or tubes) to achieve high power, which kills transparency and finesse.

More and more solid-state amp makers, from darTZeel, Ayre, the new Rowland, to Sim, as well as Pass (and many, many tube amp makers), no longer use global feedback in their curcuits. If you have really inefficient speakers or listen in a huge room, and you listen loud, then use a big Krell, etc. (even better, sell your inefficient speakers), but if you want your system to make recordings sound much more like real instruments, stay away from big amps and amps that use global feedback. You'll notice that the previous poster is recommending the 160 watt, Class A-biased Pass - not the 350, the 600 or the 1000.
I agree with Thesoundhouse. If you are set on Pass, I would go with the XA series. I too have the X350.5 and I have the Pass-addiction as well.. My friend had a pair of Amatis and he had been wanting to try the X350.5, but we weren't too keen to hoist the beast over to his house before he moved overseas.

My impression of the Amati in his system (with Einstein preamp + BAT VK-75SE monos) was on the sweet side. So I am not sure Pass would be a good fit. But with a more analytical/neutral preamp like the ARC Ref 3, it should balance out.

My only real experience with the Strads was in a Magnolia Hi-Fi in Seattle where it was driven by all McIntosh stuff, and it didn't sound too good with that combo in that room.

Ok i understand. But sometimes i really listen to extreme loud levels and thats why i was looking for a high power amp. Also i know that the first 100W on X600.5 are class A. Is that right ? And yes Frank, mcintosh stuff dosent sound to good with Strad. After i listened to X350.5 in my system i couldnt even change it back to my MC501. Is XA160.5 able to deliver extreme loud levels ? My room is like 35-40 square metters.
I agree with Raquel for the most part , some bigger amps loose finesse ect , but some mid efficient speakers come to life with lots of power , not so much watts as current . You said you listened to the X350 in your system , it's twice the watts of the XA160 , that should give you an idea if the XA160 will be sufficient in your situation . There is an XA200 if you really want to get serious . Don't forget to take into account the heat that all these babies give off .
Well stated words of wisdom, but only if genuine music quality is the objective as opposed to spectacular Hifi. I`ve come to belive that the advent of inefficient speakers has been counter productive for the persuit of natural sound. It forces one down the path of ever bigger and more complex amplifiers to drive them.

I see that you are running Coincidents - I recently put Total Victory IV's into my system and am very happy with them.


The Pass amps are very good, but for a lot less money, the Parasound JC-1 monos are a very good sounding high-powered amp. They are also fully differential balanced and should work well with the ARC Ref 3 preamp.

Again, if you want an extremely powerful amp just so you can occasionally listen to rock and roll, you are going to suffer when you are not listening to extremely loud music. And the Strads can go loud and can handle some power, but they are not big Wilsons and should not be driven extremely hard. If you really

What do you mean by "you are going to suffer when you are not listening to extremely loud music" ? If i'm listening to normal levels i should be on class A up to 80 watts.
It is not the same thing as haveing XA160.5 ?
Check the specs of the Pass amps. I think the X350.5 has about the same current as the XA100.5. The XA100.5 also has more class A watts and doubles output as impedance is halved, so 200 watts at 4 ohms. I would stretch for the biggest XA.5 you can afford, BUT your Strads are pretty efficient, though I don't know the impedance, so the XA100.5 should be plenty. Of course, you should listen to be sure.

Even at normal listening levels, peak signals can pull far in excess of 80 watts, which gives you the crossover distortion problems of AB operation. Full Class A operation has a lot of practical disadvantages (very high electricity consumption, a lot of heat, need to periodically re-bias output transistors), but manufacturers still make Class A amps, despite the practical disadvantages, because sonically, full Class A operation, when properly implemented and all other things being equal, sounds better.

In addition, all of the Pass amps, including the 160, have dozens of output transistors - on a transparent, finesse speaker like the Strads, especially given its very high sensitivity, you're generally going to get better sound using a high quality amp of 100-150 watts/channel that has a very small number of output transistors. The darTZeel, for example, is a zero feedback design that puts out approximately 150 watts/channel with only one pair of transistors per channel. The Pass is a very fine amp that has few gain stages and little or no global feedback, but you're going to hear the effects of all of those transistors in a high-resolution system.

Stards is haveing 4ohm nominal impedance so this 80w of pure class A will double ? Then 160 watts should be enough for "normal" listening levels.

That's not the way it works. Again, every time there is a fortissimo passage, the speakers can draw far in excess of 80 or 160 watts, and the amp operates in Class AB. For pop or orchestral played at "normal" volumes, this happens all the time, which means that crossover distortion is always an issue. If you are listening to chamber music at 75 decibels at the listening chair, this won't happen, but it happens all the time with pop / rock / orchestral / big band jazz, etc. Again, if it wasn't an issue, amp manufacturers would not bother to make full Class A-biased amps, which are not easy to own (enormous heat and tons of electricity - mine draws 1,400 watts at all times and gets HOT).

I suggest that you make a judgment call as to just how much loud music you listen to. John Atkinson estimated the Strad's sensitivity at 93 db., which means that it is highly efficient - you do not need a high wattage amp to make such speakers go loud, just a well-built amp (i.e., stiff power supplies) that can deliver current (it drops to 3.3 Ohms in the bass). If you intend to listen to a lot of loud music, however, why not buy a loud music speaker, for example, big Wilsons? In any event, unless you do most of your listening at really loud volume, a high-quality 150 watt/channel amp, especially one that does not use global feedback, should make you happier in the long run.
Don't get so hung up on "watt" ratings. I've read where XA60.5s were compared to X250.5s...and were preferred.

How can that be? A lowly "60 WPC" class A amp slugging it out with a "250 WPC" class A/B and coming out on top?

It's telling that XA100.5s can be had for about the same money as the X600.5s.

The XA.5 amps are just in a different league.

And I own X260.5 monos and XA60.5 monos. I run the XA60.5s daily. I really like the X260.5s, but they don't outpace the XA60.5s, and I like the sound of the XA.5s better.

Think on that: I'm not sure how much "Class A" watts the X260.5s are supposed to deliver, but the "little" XA60.5s are more than a match, even at high volume levels.

If I had the funds, I'd have all XA.5s. Whatever the class A rating of the X.5, I wouldn't care. A "smaller" rated XA.5 will more than compensate. I'd really like to compare a pair of X600.5s and a pair of XA160.5s...I know where my money would be.

Also, the XA and XA.5 amps are different machines. Try not to get highjacked by any comments about XA amps and their relative performance.
How can that be? A lowly "60 WPC" class A amp slugging it out with a "250 WPC" class A/B and coming out on top?

Pass haevily underrates the output power of all their XA series amps. The lil XA-30.5 was measured in Stereophile, and turned out to put down over 130W @ 8 Ohms vs advertised 30W.

OK i got it. But my next question is: how loud can i turn a 92db+ speaker with 160WPC on class A if im gonna change my order from X600.5 to XA160.5. I mean how many db i will have at max volume.
160watts into a 92db efficient speaker should reach 114db .

The impedance of my speakers is 4 ohms. So this means the XA160.5 will double the watts. So this will means over 320 WPC. That will result in even higher volume. I think over 114 db. Something like 117-118 db...
I suspect the XA160.5 will have more than enough power, and is superior to the X600.5 (which I owned). The extra class A power provides the ability to play music more cleanly at a high volume. The remarkable thing about extra class A is the control at climaxes, with preservation of the soundstage. If the X600.5 can play louder, it will sound more harsh and congested, and the soundstage will collapse.

You may need to be open to try different preamps.
It sounds like you intend to listen at very high volumes. The Strads can go loud, but you're talking about volumes well in excess of 110 db. You should talk to Sumiko (assuming that you live in the U.S.) or Sonus Faber to determine whether the drivers and crossover will hold up if played frequently at those kind of volumes. I ran Ebens which use Audio Technology midrange drivers like the Strads and they do not handle power as well as a lot of other drivers (in fact, other speakers that use Audio Technology drivers, e.g., Verity, Peak Consult, Rockport, are not known to be rock and roll speakers). For those kinds of volumes, I again ask why you are not using something like big Wilsons or horns.

Near my Strads i'm haveing a pair of Klipsch P-39F used for my home cinema. Thats why when i need to switch to them and to my cinema i need to have a powerful amp to drive these horns. Anyway i still want the class A watts but i want to be very sure that i can listen at very loud volumes with this XA160.5 on Strads.

When you listened to your Mac 501's, what was the meter indicating at your louder volumes?

When i'm listening to very very loud it stay at 500W and sometimes at extreme levels go up to 1000W.

That helps a lot. My feeling is that you would be better served by the 600.5 or go for the 1000.5's if you want. I've had the X's in my house and own 2 XA.5's. The XA's are the better sounding amp but you pay for quality over quantity in their case. That is not to say the X's are bad sounding, they are great but you seem to need the horsepower more.

You might come close to the best of both worlds with the XA200.5's but they will cost you north of 30 grand. As mentioned earlier, the XA.5's put out a lot more than their rated power. You might get 1000 watts from the 200's into your load. Do know this: you are punishing your eardrums at those levels. You will suffer some hearing loss if you do it too long/too often, but they are your ears.

I'm listening at such levels very rare. Almost 90% of the time the speakers are at 10-20watts but sometimes when i'm getting some drinks and want to hit it hard i kick it to 500 watts. This happends like 2-3 times a week no more then 1-2 hours. All the other time i keep it at max 5-10watts. But i still want to be able to play it very loud when i'm in that mood.
And also when i'm watching a movie on my cinema i switch my Strads to my klipsch that are hors with 99db sensitivity and i think this XA160.5 should be enough to play it very loud on that to.
Extreme levels! That's not safe.

If you listen at a lower level, your ears will open after a few minutes. You will actually hear more of the music and deeper into the recording.

The X.5 series is a relatively good value, and can provide brute force. But as Onemug said, you are paying for quantity rather than quality. The XA.5 does the power thing quite well, while also providing finesse and beauty. It comes down to priorities.

A few days ago i listened on my system the X350.5 and pushed the ARC REF3 to 60-65 and it was very loud. The amp was in perfect control of the speakers without any distortion or compression. The metter of X350.5 was over the half.
I asked Kent at Pass about the XA100.5 versus the X350.5 driving a difficult load. He told me that in listening tests, the panel preferred the XA.5 and mentioned sonics but also its ability to control low frequencies and low impedances speakers. My speakers are a 4 ohm load and only 86dB efficient, so I switched from the XA100.5 to the XA160.5. With your speakers, you should have no trouble with either, IMO. I suggest you talk to Pass Labs and then demo a pair from RENO HIFI or a local dealer to be sure before you buy.
Ive just ordered a pair of XA160.5. In max one month it should be here. Thanks for all advices and i hope i will be very happy with my new pair of amps.
Ive just received the pair of XA160.5 yesterday. The sound is very good but it still needs some break in time. Does anyone knows how long it takes for XA160.5 for full break in ?
Congrats. I still remember that the magic began after 5 days. Seemed rather stable after 7 days of continuous play. Big, open, effortless is what you'll hear with the break-in. They probably sound closed and slightly raw right now. Good, but not quite right.

To this day, I cannot tell a difference from powering out of standby vs. the end of the day of listening. This is suprising because my system is ultra sensitive to the slightest pertubation. The X600.5 needed 4-6 hours of power before they started to congeal.
I didnt power off since i got them yesterday and now they have about 20 hours of music play...10 yesterday and 10 today...and i'm gonna let it sing more. The difference since yesterday is not that big. I think this 6 big 25.000uF capacitors needs like 600 hours for full brake in ?

PS: the power is more then enough for my Strads. Playing at very loud levels and the metter dosent move at all. So this means it dosent leave class A. I just tried on some metal music at extreme loud and it started to move a little. :)
I recall the break-in was not gradual and progressive. It all happened in 2 days, after several days of little to no change.

I don't think it will take 600 hours. Maybe 200.
Thats good news! Thanks a lot for let me know
What's the verdict?
Its start to getting better after 150 hours. I dont think it is final ...still need a lot more hours. XA machines are different then X machines.

Congratulations on your new amps. I also own a pair. Mine are demos that were used about one month before I got them. I left them on 24/7 and playing music during the day for about a week. I did not notice a big change during that time. Perhaps a very slight increase in smoothness soundstage expansion and instrument air and separation.

Unlike Rtn1 though, I do notice a difference listening to music just out of stand-by mode to about an hour later (three LP sides). Now it might also be the cartridge suspension warming up a bit also. The sound becomes smoother with a bit of an increase in inner detail and harmonics. I just becomes a bit more involving. I often turn my amps on about 2-3 hours before I listen and then I'm pretty sure any improvement during the first hour is from the cartridge. I dare say it is similar to what I hear when I switch from CD to LP (sorry, couldn't resist).

Right now i have 185 hours counted on my REF3 preamp.
The improvments its not so big. I was also told from my deal to switch on and off a few times a day for recalibration of the caps. I think it will take more then what i was expeceted to. (2-300 hours). I think it can take even up to 7-800 for full brake in of the capacitors.

How many hours you have on your XA160.5 right now ? Did you feel that boom of performance ?
I've had my XA160.5's for about a year and I think they have about 900 hours on them. As I wrote earlier, I did not notice a big change during the first few months. "Perhaps a very slight increase in smoothness, soundstage expansion and instrument air and separation." Mine were demos, so they already had some time on them. I did not feel that "boom of performance."

My amps just sounded great from when I first got them and they are a better match for my speakers than were my old XA100.5's, which are also great, just not as powerful.
02-21-11: Peterayer

Congratulations on your new amps.


I often turn my amps on about 2-3 hours before I listen and then I'm pretty sure any improvement during the first hour is from the cartridge. I dare say it is similar to what I hear when I switch from CD to LP (sorry, couldn't resist).

Perhaps you need a better DAC (sorry, couldn't resist) :-)
Mine is an ARC DAC8...i dont know what peterayer has.

BTW i just bought a Kimber KS-6063 cable for speakers.
They sound superb !

How many hours for ful brake in for this cable ?
That was funny. You are right that a better DAC would improve things a bit. But you stating that "perhaps I NEED a better DAC...." is a presumption on your part. "NEED" is way too strong a word. I'm an analog guy, so even "WANT" may be too strong. I would certainly accept a gift of a better one, though :^)
Peterayer, you have a FANTASTIC system and don't need to change anything. I was just trying to be funny :-)
And that you were my friend. Thank you for the kind compliment.