[akopperl]

I appreciate everyone's replies.  I'm still unsure if they have enough power and also I am not thrilled with the idea of having to deal with 3 separate power cords.  

I had a Bel Canto eVo 6 (1st genaration) in my system.  I used it to power a 5.1 system (bridging 2 channles for the center) and it appeared to have enough power (rated at 120 wpc except for the bridged channel).  I loved the amp, but decided to sell it after the gen II was released while it was still holding much of its value.  Also, I had separates at the time and was changing to a 7.1 system and wanted a 7 channel amp.

Since the Bel Canto, I have tried several solid state designs and they just always sound a little too bright for my liking.  I am interested in going back to a digital/switching  design since the Bel Canto was probably my favorite amp to date - but the Bel Canto is a little pricey for what I am trying to do today.   Fortunately, I only have to power the front 3 channels as I will use a receiver to power the 4 rear channels.

Right now I am considering the NuForce amps and a Butler 3150.  The Butler is not digital, but has a tubed output stage and is supposed to be very smooth (non-fatiguing).

Thanks

[Carlman]

Right now I am considering the NuForce amps and a Butler 3150. The Butler is not digital, but has a tubed output stage and is supposed to be very smooth (non-fatiguing).  ...

Interestingly, I'm comparing the Nuforce Ref8b amps to the Butler 2250 right now.  I'm using a TacT 2.2x preamp and have been switching between them today.  All this gear is on loan from my dealer.

My preliminary thoughts on the sonic personality of the 2 amps is a bit surprising.  The Nuforce pair is more tube-like in its presentation than I expected.  It has a good 'kick' to it as well... and it has PLENTY of power in my room. (only 11x13)  It's like a good combo of SS and tubes.

The Butler is similar but has a 'softer' sound to it.  It's not as punchy but it is powerful.  If you want more of a pillow-satin-smooth sound, this is it.  If you want a tight, punchy sound that's also smooth, the Nuforce's are likely a better option.

I haven't heard either amp run out of gas in my room, on my speakers.  Either has more than enough power.  I haven't decided which I'd prefer yet.  I wouldn't be upset with either.  

With the gear in my room right now, there's no real loser...  But with the room correction and amps I'm demo'ing, there's more 'flavors' than I've ever had possible in one sitting.

Look for more feedback about this gear from others in the NC Circle after tomorrow.

Hope this helps a little,
Carl

[Rocket]

Hi,

Just thought i'd add my 2 cents worth and comment on the post from loose and werticus' response  .  I really think it is up to the individual to read between the lines and ascertain the merits of a persons posts.  Hey, i've been guilty of upbeating particular products because i was excited by the sound i was obtaining, however look at my comments regarding the stock ps audio hca - 2.

Anyway i really like the nuforce 75watter and my comments were in regard to its price of $1500au which was amazing value.  At those prices in australia you can only buy nad/rotel/denon.  

I think the nuforce ref8's have replaced the bel canto evo gen2 monoblocks at the local dealers shop in perth.

Anyway back to my fully modded ps audio hca -2 and no i'm not going to compare it to the nuforce amp, i'm off the merry go round for a while   .

Regards

Rod

[Occam]

...As WerTicus said, anyone can use a linear power supply to upgrade Ref 8 for higher power and it is easy to do. But then you're stuck with some ugly transformer and by the time you're done, you probably spend too much time on it to be worth the effort. And you can't stack them nicely for multichannel setup or bring it to your friends house to show off  

Actually, all things being equal (i.e. rail voltages), there are some rather compelling reasons, both technical and economic, to prefer switching powersupplies for producing bass frequencies below 2xline frequency (100 or 120hz). A major reason linear supplies have such honking big capacitors on the rails is that these are what provide power for bass. These provide the joules of energy to power bass excursion, but they are recharging only 100 or 120 time a second. Energy storage of caps is linearly related to the charging frequency, and as switching supplies recharge their caps at frequencies orders of magnitude higher, they can have tremendous advantages. This may well a factor in users reporting excellent bass performance in the Nuforce, in spite of less than spectacular rms characteristics.

And furthermore, I don't find transformers ugly at all, I find them rather charming in a retro sort of a way......

[WerTicus]

hehehe retro, thats funny occam  

but yes i have never heard anything that comes even close to the bass performance of nuforce, they make EVERYTHING sound slow.

but i wonder if the hi frequency 'issues' some people are having would be solved by having a traditional supply... hrmm.

[nuforce]

I was away for the whole weekend and saw quite a few posting. Occam is exactly right about the reason for switching power supply's performance. We elaborated it more on our website under power faq.

With Ref 9 (see spec on website), I think combinning it with Ref 8 will be a very good match for home theater use. By the way, all Ref 8 users will be receiving 1/4" faceplate for free!  

There is no need for existing Ref 8b or Ref 8 users to rush to upgrade it to the so called "Ref 9" spec. The amp as it is now is very good and what we have done to Ref 9 is pushing the limit further.

Jason

[mmakshak]

I can't help but jump in here.  I really don't have any real experience with high-end amps, but I think damning the Nuforce based on what other people say is a mistake.  If you listen to it, you will know it is something special.  Currently, I think I have a later version in one channel and an earlier version in the other.  Could I live with this?  Most certainly, but these guys are saying an even better version costs $15.  Doesn't anybody get it?  These guys are the Ford Model T(was that the correct model?) of amps.  They are bringing extremely high-end sound to the masses.

[mmakshak]

Now stick with me here-no matter what your politics are.  I remember C-Span playing about twenty speeches in a row, where Clinton said reducing the deficit was the most important thing.  When it actually happenned, people said it was Greenspan or the Republican Congress.  But guess what happenned when he left office(remember that he actually created a surplus).  Greenspan and the Republican Congress were still there.  I understand where he put Cuban cigars weren't the best place, but he actually did what he said he would(which is unusual for politicians).  This(if you are still with me) is analogous to when you hear Nuforce.  Take your most familiar cd's(although I don't believe in cd.) or records, and when they sound better than you've heard before, don't ascribe it to the speakers, cable, or source.  Keep your skepticism, but don't automatically ascribe the situation to other things.

[loose]

makshak

Who's "damning the Nuforce based on what other people say"?  98% of this thread is raves.  I can't recall a single instance of anyone "damning" the NF.  A very few, like me, have rejected the over-the-top claims of serial hyperbole-merchants like werticus - and in my case, this was based on a critical appraisal through auditioning the product - and called for more measured responses.  

Far from "damning" the NF, most of this thread has served to elevate it to an impossibly rarified status with extravagantly bloated praise.  This detracts from the credibility of the posters concerned, and also possibly the product, since anyone reading the unqualified gush of the Holy Grailers will in all likelihood bring unrealistic expectations to any subsequent audition.  Fortunately, the word from the horse's mouth - Jason - is more tempered, while still being fired with excitement and enthusiasm over his company's product.  A lesson here, for some.

[nuforce]

We at NuForce are perfectionists. For those who think NuForce is good, but not quite there, I challenge you to evaluate Ref 9 (or the updated Ref .  Oh well, you can't evaluate Ref 9 yet until after August 15.  A few pre-production units are out there...but we have just posted the production Ref 9 photo. If you are willing to pay extra color setup charge (varies from color to color and depending on number of units), you can have it in any color. May be your wife will let you display a stack of pink color Ref 9s  

I will start another subject on NuForce Reference 9 to contain the rumors, get fresh new feedbacks etc. I think people like audiojerry should audition Ref 8 again as it has come a long way.

Jason

[WerTicus]

oh dear its happening again

[igroucho]

Pretty natural state of things that in a thread dealing with a new product you will find an overwhelmingly number of praisals. Critics and bashers will be in minority. For this reason nothing to lift even an eyebrow over or you're being naive. And even more natural is that in this case we are dealing with a product, more or less revolutionary in its design and at great value for the money! Suddenly hi-end became affordable to more or less common people and a secluded market is challenged at its core. This doesn't sit well with some folks who want to preserve the secret handshake club.
But then again, in audio specs are one thing and personal prefs are another. If you don't like the sound of Halcros you don't.

[audiojerry]

For those who don't recall, or were not around at the time, I was one of the early auditioners. In short, my review included some positive comment on its virtues, but the bottom line was that the Nuforce was not in line with my preferences and did not compare favorably to my personal amp.

Jason and Nuforce deserve credit for accepting my criticisms in stride. Instead of becoming defensive or trying to discredit my ability to listen, a tactic that other manufacturers on this forum have resorted to, Nuforce went back to the drawing board and have continued to try to refine and improve.

I try to keep an open mind, and I'd be interested in finding out how far Nuforce has come.

[JAMn Joe]

Hi audiojerry,

You're more than welcome to come down and audition the Ref9's once they arrive. I'm putting in the order today for the new units having already heard the beta Ref9 and expect them to be here mid August.
You're only a little more than an hour a way so PM me if your interested.

Joe

JAM'n Audio

[nuforce]

Audio is very complex but so far we have been able to corelate the listening experience with the science.  There is no perfect amp yet and everyone has a preference. So, even for a very good amp such as NuForce, we find that a lot of people raved about it because of a good bass, sound stage etc.  High freq imaging WAS a weak point (compare to some of the best) and it has been pointed out by a few people. Sure, there are many who find that it is good enough due to their setup, music preference, ear characteristic or whatever. We enjoyed bathing in their praises   . But the science doesn't lie.  I wonder why icepower datasheet doesn't show THD+N vs Freq at various power rating   . And the spec only showed THD+N at 1Khz, etc up to about 7khz. hmm...

For those who follow the plots, each upgrades showed significant improvement in measurement and that corelate to listening feedback.
With the latest upgrade, we have taken measurement that showed THD+N at 0.03% at 20khz at 10W for example, with a 40khz filter (ie no cheating).  As a comparison, the version that was first audition by some people has THD+N at 0.16% at 20khz at 10W (even this number is highly respectable).  I doubt any other switching amp or few linear amp can achieve 0.02x% THD for 20Khz. Recent listening test have confirmed the improvement in high freq imaging.

But good sound reproduction is more than just THD+N and freq. Harmonic and power plays an important part too.  We didn't just bring down the distortion and noise to an astonishingly low level (we are still trying to confirm our SNR of 90+ to 100db and that's amazing for a switching amp with switching power supply), harmonic has cleaned up.  Many people wondered why NuForce with 100W rms sounded as loud as some 300W linear amp and that's due to the fast response time of the SMPS.
Someone demo NuForce Ref 8 recently at a show in Chicago (related to AV123) and someone was wondering where did we hide the tube.

NuForce has zero phase shift and near zero output impedance at ANY frequencies and that's the reason it matches well with many speakers. We know that Current hungry speakers (Apogee) will not be a good match for Ref 8 due to its SMPS Current limit of 2.1A.  The amp's power can be estimated with V square / 2*load but SMPS will current limit even though it seems that there is enough power if you rely on voltage for power calculation.  To address this problem, we put in a 350W RMS SMPS in Ref 9 with voltage limit at 52V and current limit at 7.3A.

With all the rapid improvement, we're exhausted and need to chill out for a while

[Russell Dawkins]

I would say you've earned the right to take leave with pay for a while, and should! Congratulations on an auspicious entry into the market.
Russell

[studley]

We know that Current hungry speakers (Apogee) will not be a good match for Ref 8 due to its SMPS Current limit of 2.1A. The amp's power can be estimated with V square / 2*load but SMPS will current limit even though it seems that there is enough power if you rely on voltage for power calculation. To address this problem, we put in a 350W RMS SMPS in Ref 9 with voltage limit at 52V and current limit at 7.3A.

Jason
I have Quad 989 speakers.  They have sensitivity of about 87db but are not easy loads due to their impedance curve which I understand drops well below  8 ohms.  I am planning on auditioning a pair of 8Bs.   100 watts is enough for 87db (my current amps - Aleph 2s - are 100 wpc) but I'm not sure how "current hungry" the 989s are.  

You have to forgive my technical ignorance but does a difficult load in terms of impedance equate to being current hungry and might, therefore, the 8Bs be a bad match for my 989s and other such "difficult loads" ?

BTW the Alephs are great amps and I will be very impressed if the 8Bs can better them!

[nuforce]

ESL-989
If it drops to 1 ohm, then you will find Ref 8/8b inadequate.
The spec said the impedance is 8 ohm.  

Jason

[studley]

Jason
The spec does say 8 ohms but its said that that is not the full story . .
I very much doubt though that they go down to 1 ohm.

Just for my clarification, does current hungry equate to low impedance?

Thanks

[nuforce]

Just for my clarification, does current hungry equate to low impedance?

In general yes, but a speaker's impedance and current requirement is more complex then a simple explaination so I included a response from our CTO below.  Follow the speaker manufacturer's recommendation for amp power requirement.

Jason

From more technical people at NuForce:

What matters is whether there is any clipping of output voltage to the speaker due to its dynamic loading and instantaneous current.

What is the instantaneous current going in or out of the speaker? That depends on the amplified audio voltage applied to the speaker, its reaction (Back EMFs) and its impedance, which is very complex and not constant in time due to the speaker’s interaction with the room’s air and walls.  Yes a speaker is also a receiver of room’s acoustic energy and one can actually see voltages across its terminals when it is exposed to sound waves.

Because of multiple drivers in a typical speaker, there’re many back EMFs due to the existence of coils moving in magnetic fields.  Depending on the time, the biggest back EMF generator is the woofer, its back-EMF can have the same phase as the driving voltage and effectively makes the speaker current higher than the simplistic formula I = V/Z would indicate.  The measurable speaker current is the vectored sum of many (V-EMF)/Z, keeping in mind EMF is not in phase with V which is the reference phase.  Now V is not a sine most of the time, but most critically an impulse at the attack of a sound segment. That creates an impulse of sound wave that gets reflected by the walls of the room back to the speaker membrane which in turn generate an impulse of EMF not in phase with V, perturbing V.  The control loop then tries to correct to maintain V at what it should be at that particular instant.  And that may result in a very high speaker current virtually impossible to predict by simple vector math, but can be measured.

In all this the rail voltage has little to do with the speaker current except if the storage capacitor gets drained of its charge and droops its voltage sufficiently to cause “clipping” in the sense of not allowing the control system to maintain the speaker voltage at what it should be at that instant, therefore the speaker voltage wouldn’t match the audio source voltage.

So while (V-EMF) can be higher than V in absolute value, Z can be smaller than the speaker’s nominal impedance due to different LC combinations, therefore the externally measurable speaker current can be very high, much higher than say Vrail/R, R being nominal speaker impedance which is really meaningless in most cases.  Using an ohmmeter to measure a speaker impedance only shows its DC resistance, typically of the woofer coil, but not its real Z which is very complex.