[_scotty_]

Jason,it is considered a virtue if an amplifier can behave like a voltage source.  If  the amplifier will deliver a constant voltage into a load regardless of the loads impedance.  For example,if the amplifier will deliver 100watts RMS into 8ohms,200 wattsRMS into 4ohms,and 400watts RMS into 2ohms, it can be said to behave like near perfect voltage source into real world loads which can show dynamic impedances even lower than 2ohms. This ability is a good indication of how robustly the power supply is designed and gives the amplifier the ability to better deal with  the loudspeakers it may be matched with.  The fact that your amplifiers do not have this characteristic  is something to be noted when comparing your product to that of your competion.  Welcome to AC, I look forward to your presence in the forums.
Scotty

[nuforce]

The amp is designed to be an ideal voltage source, and unlike Tripath, we are impervious to speaker load (explain more later).  While we can argue about the doubling of power when impedance drops to 2-ohm, we are still talking about measurement using a big load resistor and compare raw voltages.  Much like comparing Horsepower without the right context (a 500HP Caterpillar may not run like a 100HP Honda Civic).

For example, without a constant switching frequency and a robust closed-loop response, the Tripath technology will have variable conditions at different frequencies, plus the interaction of impedance at different frequencies, thus resulted in a bit of mess (The Q is all over the place).   In NuForce design, the closed-loop response makes sure that at the end of every cycle, the net error is nulled out at a speed of 1Mhz, practically nulls the variance at the speaker terminal, so we behaves closer to ideal voltage source at much higher frequency without running into instability.   In conventional Class-D design, you'll notice that many of them open-loop, and have severe phase shift so it has to be strongly filtered at 20Khz to prevent instability.

For more detail, please examine the comparison between various technologies posted in nuforce.com

In the raw power department, we simply put in an off-the-shelf SMPS that is current limited to 100W.  So regardless of 8, 4 or 2 ohm, the SMPS will supply 100W of current juice before the current limit kicks in and shuts down the supply.   But during the instantaneous peak, we can swing a doubling of power when the speaker impedance halves.   If we have a limitless power supply obviously, we can doubling up the power all the way (up to 1152W@2 ohm peak).   In fact, one of our OEM application we are driving a pure capacitive load (which is why NuForce amp works exceptionally well with ribbon, and ESL).  With our reference speaker, we have been playing music without clipping, with peaks of 300W+ from the 100W amp.

[lonewolfny42]

Maybe we should persuade the Nuforce folks to offer some kind of audition to AC  

Good point Jerry....best way to hear what it can do in your system...and also get a few reviews !!!

[nuforce]

Ok ok, if there's enough requests, we can send a pair out for you guys/gals to pass it around.  Those who want to audition it please email to NuFoce (go to "Contact/Sales" on www.nuforce.com and click on the "email us") with email subject title "Audition".  You need to promise to write a review with photo.  There will be a lot more reviews coming soon.
Note that NuForce amp is very sensitive (those reviews you saw on our website are 100% honest reviews from our customers, we didn't influence them) and it will pick up any flaws in your system. In our listening lab, the souce comes from a CD player upsampling to 192Khz by Apogee DAC and directly into our amp.

Here's how the US only audion deal works:
(sorry, no international audition, too much trouble)
You send us your request with name, address and phone number.  Indicate how you want to pay for shipping (typically $10 to $15 via 3 days FedEx for US): Paypal or Visa/Mastercard
We'll send you a 70Wrms Ref 8. 70Wrms version will not be produced after we clear out the handful of units in our inventory, 100Wrms has been sold out until April 15.
You'll receive an invoice with online payment link. Make sure your billing address and shipping address match.
We will ship you a pair for audition after you pay for shipping. You have to send it back within 2 weeks after receiving the amps (ie, you have 1 1/2 week to audition and then send it back)
This is a first come first serve. The first person who email us will get to audion first. Second person will have to wait and so on.
If you don't send it back after we reminded you, you will be charged for the full retail price minus 15%.
NOTE: we won't sell you the amps if you live near a dealer.

[Rocket]

Hi,

That is a great idea lonewolf and an excellent offer from jason.  Luckily i live close to the oz dealer and can have a listen to it in my system if i need to.

I need to point out that i have nothing to gain from my initial post but have provided this information because i was pretty amazed at how good the amplifier sounded.  After all if we can save a few dollars and get a great sounding amplifier all the better.

Regards

Rocket

[lonewolfny42]

Hi,

That is a great idea lonewolf and an excellent offer from jason.

Rod,[/list:u]
Give credit where credit is due....audiojerry brought it up first. But we have had many home audition tours running at AC. And the companies get some good feedback with our take on their product. So its a win - win for all.[/list:u]
Thanks Jason for your offer....sounds good. [/list:u]
Chris[/list:u]
Ohhh, Jason....what if you don't have a camera ? [/list:u]

[nuforce]

>What if you don't have a digital camera ?
Oh man, you people. If you don't have a digital camera, skip the photo for the review.

[audiojerry]

I must commend Jason for having so much faith in his product that he is  willing to offer a review sample without hesitation.

Chris and Rod, you guys are great facilitators.    

I'm not sure if I got my request for an audition in on time. I wasn't able to access the Nuforce email server.

[guest1632]

Hi, I was informed by a user that we're generating some buzz here (and may be everywhere).  I will like to thank many users for their feedback and posting.  Let me tell you a little about us and also try to answer some of the questions.

We're a new company and have been working on power conversion and amplifier for the past 3 years. Our CTO was the principal architect of the Tomahawk cruise missile power system and he designed many highly reliable power and control systems.  Switching amplifier design is ...

Wow! Ok, gotta ask this, but are you guys gonna build a stereo version, having two monos in one box, thus saving some money in the case design?

Ray

[nuforce]

We don't plan to introduce stereo amp in the foreseeable future.  We plan to introduce 350Wrms amp (mono), preamp, and a few other supercool stuff that we can't disclose at this point.  Every product that we introduce will outperform just about everything in its category at a fraction of the price. If we can't do that, it is not worth doing it.  For example, we plan to introduce a 1000W to 2000W AC Regenerator weighing less than 5 lbs based on our patented Class-N circuit in 2006.

[guest1632]

We don't plan to introduce stereo amp in the foreseeable future.  We plan to introduce 350Wrms amp (mono), preamp, and a few other supercool stuff that we can't disclose at this point.  Every product that we introduce will outperform just about everything in its category at a fraction of the price. If we can't do that, it is not worth doing it.  For example, we plan to introduce a 1000W to 2000W AC Regenerator weighing less than 5 lbs based on our patented Class-N circuit in 2006.

Hi, What is this "AC Regenerator" and just my opinion, it's be nice to have a stereo box of the 70W version. You already have the R&D done. Sell it for a grand, and I don't think you could keep them in stock, especially when word gets out on the sound. Are you guys gonna put together an integrated? Sure Hope so.

Ray

[lgeis]

That's a very enticing trial offer from Jason. I can't help but think the amps' very low weight and small size facilitates shipping them around. Couldn't do that with Levinson or Krell.

I don't have time to audition or I would...have my own company to run, and I know Jason will sympathize with that. But I'm extremely interested in anyone here testing these out with either Vandersteen 2's and 3's, or VMPS RM40's (a recent discovery I'm considering), both with music and HT work.

At $1500 or so a pair, biamping is a no-brainer. Good thing from my point of view.

[JoshK]

i sent a reply, i'd be happy to do an eval.  I think I am to a point where i can actually give a fair eval.

[Agisthos]

We plan to introduce 350Wrms amp (mono), preamp, and a few other supercool stuff that we can't disclose at this point.  Every product that we introduce will outperform just about everything in its category at a fraction of the price...

That is the dream for budget concious audiophiles. Some of us just can't afford 10k amplifiers so it is exciting when a product comes along that claims to offer the high end performace for only a few k.

Jason you said you put in an off the shelf SMPS. No tweaks or specific audiophile type design? just a standard part?

How much do you think the 350w mono's will be when they come out? Also with this amp design do you feel that the higher rated 350w will have superior sound quality or is it just a matter of more power to drive less efficient speakers?

[nuforce]

We think that NuForce Ref 8 is close to perfection, but there is still some room for improvement.  A lot of good amps out there have some minor imperfections (less gain in the high freq for example), and that resulted in having a boost in other freq range (stronger bass for example). NuForce amp is very pure. And after a very short while, you'll begin to appreciate the true reproduction of the signal. Ok, I don't like to brag. As we collect more reviews, we'll let you know. I am sure you're hear from the first person who audition the amp next week.
So where can we improve ?
1. Let user select whether they like a tube-like characteristic or the original pure and perfect amp
2. Continue to reduce distortion and noise. There's only so much to do there and beyond a certain point, it is not noticeable by any human ear.
3. NuForce amp is a true close-loop system and it takes the feedback from the speaker terminal to zero out the error at every cycle. The next level of improvement could be to sense any distortion from sound in the room and feed it back into the modulator. Nobody has ever done that. That will be a huge breakthrough in audio engineering. Ok, we're not going to be able to do that anytime soon . May be 2006 or 2007. May be it can never be done.

As for 2005, the 350W version will be more expensive, may be around $1400 per unit versus $800 for the 100W RMS.  It will be the same as the current Ref 8 (if we can make any improvement, we will).  Actually, Ref 8 circuit board is designed (and has been tested) for 300W.  100Wrms is more than enough for most speakers. Keep in mind that Ref 8 has peak of 288W and avg per cycle power of 144W for 8 ohm load.  Read the power faq.  There is no switching power supply on the market that can deliver 60V for audio purpose (telecom switching power supply is too costly). Therefore we designed our own and that explain the delay in introducing Ref 9. Ref 9 will also include both RCA and XLR and have a very nice chassis.

Perhaps instead of using multiple Ref 8 for bi-amp or tri-amp setup, you can use a single 350W Ref 9 for that.  Or you might need Ref 9 for some really hard to drive speakers.

We think monoblock offers the most flexibility. You can try the 100W versoin initially. And buy more monoblocks for bi-amping. Or use the 100W for surround channels and upgrade to 350W for main speakers.
If one fails after a few years, you only need to buy another monoblock (from NuForce offcourse ).

[Agisthos]

Tell us a bit about the preamp that you have coming.

I notice that you say in your development you are running the cd input directly into the amps, but I have always found a good preamp will bring something more musically to the sound

[nuforce]

The reason we're not using a preamp in our current test system is because we can't find a reasonably priced preamp that will not distort the sound. Well, we have different purpose for our system. It is used to do listening test (we do measurement at the lab too) and we find that the Apogee miniDAC is slightly better than a good preamp.
Preamp is what it is. The goal is to have as little distortion as possible. We don't know how well NuForce preamp is going to be. It is not completed yet. Price wise, we're looking at about $1600 retail (with remote control) and release date is estimated around September. It it doesn't meet our standard, we won't release it.

[nature boy]

Jason,

Thanks for offering a home audition to AC members, I am signing up!

Audiojerry & Lonelywolf,

Thanks for encouraging the the home audition!

NB

[cab]

Try looking into any of the transformer based volume control/ preamps. Bent Audio and several others have them. They are relatively inexpensive; most people who hear them find them preferable to other preamp methodologies....

[Wombat_VC]

What is the input impedance of your NuForce Reference 8?