[Mad DOg]

I only wonder because of how almost everybody says the sound of passives is really clean but there is a lack of dynamics and bass with them.

not every system is passive compatible. choice of interconnect from preamp to amp is important as the wrong interconnect can present associated capacitance driving problems. there are other things that need to be considered as well which are addressed in the excerpt below which is cut and pasted from the EVS website.
 
1. How do I know if I am passive compatible?

Passive preamps (attenuator/volume control) do not work in every system.  Here is a
very general rule:  If you have a 2 volt CD source (player or DAC), an amp with at
least 26 db of gain (20 times), speakers at least 88db sensitive and don't listen screamingly
load and don't have a huge room, then you are probably passive compatible. Any one
perimeter not met and it may not work.

The best passives I have heard are the nude stepped attenuators from Scott Endler and Ric Schultz.

http://mysite.verizon.net/vze4c5pt/id2.html
http://www.tweakaudio.com/Ultimate%20Attenuators.html

I've had experience w/ the CIA, Bent, and Placette passives...These stepped attenuators have worked better than any of these in my system. They do not lack dynamics or bass at all. in order to surpass the performance of the stepped attenuator, IMHO you'd have to spend over $3K for an active linestage that can match it w/ the same type of transparency, purity of tone and dynamics.

[Mad DOg]

toroids are far less offensive than iron core transformers.

a designer once told me that he preferred to use iron core transformers because the generated field can be "tuned" or "positioned" by placement and rotating it so it interacts minimally with other critical components. toroidal transformers generate an even field around the entire toroid that can not be controlled by rotating the position.

[Occam]

I only relay what my em meter tells me.  You are right however, toroids are far less offensive than iron core transformers.  My meter goes off the scale when it gets near those an iron core . What other issues do transformers create? .....

Any meter will go off scale if you set that scale low enougth. What meter? What are you measuring? At what distance? With respect to toroids and 'EM', its not a problem that a can can't (literally and figuratively) fix. If you'd like to discuss the pros and cons of different powertranfomer implementations, feel free to open a "Power Transfomer Tradeoffs" thread in the Lab circle. There is far more than EM....

I asked for a further explanation and you've told me nothing.  You're obviously not overly familiar with transformer technology or characteristics, so why tout  the product you sell with such silly comparitve claims?
Its well and good for you to share your sincere subjective views as an audiophile, but as a vendor, you really should try keep the objective, actually accurate and verifiable, or at least sensible. You are held to a higher standard than a hobbyist.

[Phil]

Tweekgeed or others, I'd be interested in whether you have powered the nuforce with balanced power.  I find that balanced power generally helps reduce the noise significantly and can support efficient amps.


WeTicus,
what kind of amp were you using before the nuforce?

thanks.

Phil

[WerTicus]

I haven't heard any typical RFI grunge and harshness issues at all with these amps.

 

I have in the first 30 seconds or so of turning them on , some wierd almost radio interference sound comes throught the tweeter and then once they have turned fully 'on' it goes away...


Before the nuforce I was using a rather large and heavy class A/B with 255wrms on tap, it had two 300va torriodals, it was using me340/350 pairs of mosfets and occam actually helped me to get it to sound half way to decent with some minor mods.  It was compared to be on par to the ASKA 100w with the works, at a listen off at my local.

The 70w nuforce is light years ahead of it - with technically more peak power on tap the nuforce can drive the speakers to what seems to be a louder volume (not measured) but at the same time remains so much clearer than the old amp even at low volumes.

I also cannot get over how fast this amp is, drums are just real.  And how separated the sound stage is - truly amazing.  This comparision holds up vs the rather good belcanto amp too.

[cryotweaks]

There is probably an explanation for it, I do not have one.  However, I leave them powered on all the time.

[guest1632]

Go to market square and vote for NuForce manufacturer circle.
I think that's how this place works :).
By the way, it is NuForce, not newforce.
I am glad NuForce becomes a popular discussion here. We will certainly help out with the cost of running this website (that's what the FAQ said, this place survives on donation :)).

Jason

Hi Jason, Sorry about the misspelling. My speech synthesizer pronounces them both either way, so did not look at the spelling.

Ray

[_scotty_]

Mad DOg, A toroidal transformer radiates more of its field in a horizontal plane than a vertical plane. The field is donut shaped.  If you mount it on edge you can lessen its potential interference with nearby circuitry. It can also be shielded of course.
Scotty

[nuforce]

Turning on NuForce amp - if you first power it up without any music, then the amp is not fully on (that's why you might hear some strange very low level noise, no harm).
In the Instruction sheet, we mentioned that the proper (and logical) way to turn on the amp is:
1. Turn on the amp (don't play any music)
2. Play music to fully power up the amp (it takes 2 seconds).
This is a one time event. It doesn't power down anymore.  If you leave the amp on all the time, it consumes 6W during idle.

One of the reason this amp is so fast and accurate is that the output signal from the speaker terminal is being fed back to the modulator and any error is corrected at every cycle.  And the bandwidth helps (you can actually use NuForce amp for ultrasound application. No kidding. It can drive pure capacitive load).
For many switching amplifiers, they use clock generated PWM waveform and that requires a 50 or 100 to 1 ratio between the switching freq and the audio bandwidth. Therefore it is a huge challenge for those amplifiers. If they increase the clock too much, the high power components can't switch that fast (to get 20khz audio bandwidth, they have to switch at 1Mhz).  There are also a lot of noise when you switch that fast.  It is difficult for many switching amp to have good high freq sound.
NuForce is clockless and the switching freq to audio bandwith is 5 to 1.
There is another big advantage related to phase but too proprietory and we can't discuss.

[mr_bill]

Hi Jason of NuForce,
When will the balanced version of the monos be ready for order?  (the model on the website)
When will the high powered version be ready for order and will the price be $2800 for the pair?
Thanks,
Bill

[WerTicus]

also i understand that my 70w version can be upgraded to 100w with a power supply change?

does this apply to the 350w version also? is it just an upgrade?

[nuforce]

Ref 8b is available for order NOW (limited quantity)
Ref 8 is out of stock (no dealers have any inventory except may be their demo pair)
We are going to SUBSTANTIALLY increase production (again!) and will fix this inventory problem by end of May. Supply will remain tight until then.
It takes 3 to 4 weeks to schedule and complete a production run and smaller batches from previous schedule are being completed in the next two weeks.

Some of the 70W Ref8 that has the "colorful" faceplate (collector's item someday?) can not be upgraded to 100W.  Those "newer" 70W Ref8 with the same faceplate as the STANDARD 100Wrms Ref8 can be upgraded to 100W but we have not decided if we want to do that.  This is a BACKDOOR to get the 100Wrms for cheap!  Right now we so tight with supply so don't contact us about upgrade.  Enjoy your 70W version if you are the "lucky" few who got it. Contact us in a few months and we'll see what we can do.

350W Ref9 - estimated time of arrival is end of June.  This little baby will still weight less than 5 lbs but with 350Wrms, 900W of peak into 4ohm load.  Are you running a concert at home ? Some very hard to drive speakers will need Ref9.

Kid you not, next year you will see 500W to 2000Wrms amp weighing about 5 lbs (yes, still tiny). Not sure how's the performance of these monster amps as they're based on a totally different class (NOT Class D). Come on, nobody need this much power at home   Be nice to your neighbor!  They might be good enough for clubs and concerts.

BTW, do you know that if you're the DIY type, you can purchase the parts from nphysics.com and put together your own stereo version or multichannel amps in a box ? Don't send email to NuForce about parts. Contact Nphysics.  You can inquire about pricing, but everything is out of stock.

[Occam]

...There is another big advantage related to phase but too proprietory and we can't discuss.

So, you'd tell us, but you'd have to kill us?
I really do like this 'drama queen' approach to marketing......

As proprietary as 'it' may be, there is quite alot of public information available. Mr Tranh's initial patents on the technology -
http://v3.espacenet.com/results?sf=a&FIRST=1&CY=ep&LG=en&DB=EPODOC&TI=pwm+controller+single+cycle&AB=&PN=&AP=&PR=&PD=&PA=&IN=&EC=&IC=&=&=&=&=&=
As well as Nuforce's parent company's website
for descricptions of the innards of the Nuforce products, and some prices -
http://www.nphysics.com/products.htm
and their technical section -
http://www.nphysics.com/whitepaper-scc.htm

From my limited experience and time on those issues relating to Nuforce's previous comments on a compettitve technology, spcifically the Ucd based products, I'll make some obvious comments -

1. Both are self oscillating sytems taking feedback after the reconstruction/output  filter. While the Bruno Putzey's original Ucd patent did not fully address that 180o phase lag issuse , the actual implementation adds a passive pole to the feedback loop in addition to existing 2nd order output filter. It is simply not an issue with regards to the Ucd implementation.

2. NPhiysics choice of a BTL (bridge tied load) single rail and Ucd's choice of of a split rail half bridge is not specific to their loop control methodolgies given in their patents, but rather a design choice made for engineering/ecomonic reasons. Either loop control method coud use either rail/output topology, and both have their pros and cons. Similarly, the respective choices of swiching and linear supplies are design choices not specific to their contol loop patents.

3. Mr Tranh of NPhysics is one heck of an impressive guy, as is Bruno Putzeys of Ucd. Their technologies, IMO, are the current practical state of the art for switching amps. Both (among others) can yeild impressive results, and it would depend on the care and expertise given the implementation.
FWIW

Apologies for any innacuracies, but my only source of relevant information has been those rather dry, dense patents. And no doubt, both NPhysics and Ucd are pursuing techniques that are only covered and described in patents pending.

[nuforce]

Hey, Occam, good job .  Yes, Tranh is the genius behind our company. He symbolizes the classic old school garage style entrepreneur that we don't find these days.  Unlike some well funded startups with big credentials, he started doing his own R&D in a tiny lab in Santa Rosa, CA.


I am on the right:


Don't worry, we not going to be ran over by some giant.  We are well funded and the vultures are circling now...

Jason

[_scotty_]

Occam, It would be nice to know how the issue of current shoot through was handled and if the amplifier has a deadband time like the Tripath
or if they circumvented the problem and the resultant crossover type distortion
at the zero crossing point.  This is one of the weak points of the Tripath technology that leads to a slight dryness and lack of liquidity compared to the best analogue amps I've heard.
Scotty

[Occam]

Scotty, digital control theory ain't my thang, and to be honest, I developed a whopping headache trying to wade through the patents and I didn't get all that far. Patent writing is the most obscure and opaque, sort of the worst of both engineering and law. As I said, I really only commented on the obvious.

At some point of severe masochism, I'll revist the patents. I would assume that implicity within any feedback scheme  it would at least peripherally address/acknowledge deadtime, shoot through issues as they effect distortion and efficiency. I can only suggest you go to the patent site I referenced, and look at the 'claims' for mention of areas of interest. Then you look through the patent for specific claim support and justification, and try and figure out WTF they're talking about.  

Or perhaps Nuforce could address your question.

[Agisthos]

Jason,

I notice on the website you guys are recommending the Stealth Power Cords for your amps.

Obviously you must have listened to a rnage of power cords before settling on that one. How did that go and what did you find?

Where there any ehhh, cheaper ones that you guys liked?

[Agisthos]

Don't worry, we not going to be ran over by some giant.  We are well funded and the vultures are circling now...

Jason

The last thing we want to see is a great new technology being bought out by some Mark Levinson type company and then have to start paying 5 grand for the exact same product in fancy casework.

[nuforce]

I am listening to a demo pair of 70w Reference 8 amps. My speakers are Von Schweikert VR 4 Gen III SE rated at 89dB, and I am using an APL Denon 3910 with volume control running direct to the Nuforce amps. I also have listened through a First Sound Presence Deluxe II preamp, but I prefer going direct.

I have noticed two things that I'd like Nuforce to address, if possible.
1)At low volumes, the dynamics "collapse".  The amps don't bring my speakers to life until I turn the volume up to nearly "live" vol ...

Where did you get this pair from??   If you have a pair with the 5-way binding post, they have a protection circuit that was set too conservative.  If you have the new unit with the Cardas Patented speaker connector, then it's the 70W power supply running out of steam.

As with all volume control, at lower level, they lost resolution.  I am not sure how APL implemented their volume, whether it's contant gain, decimation, etc, etc.  Unless you are talking really, really low level signal, otherwise, this may be system dependent.

Casey (the guy in the middle...)

[_scotty_]

tvad4, what volume does the amp you normally use stop sounding dynamic or lifelike and what brand is it and what is its rated power? Do you know what the impedance curve of your VR4s is?  The amp you are using only has 70rms watts available to drive your speakers regardless of how low their impedance curve dips, this may be part of what you are hearing. Do you have any idea what your SPL was when you heard the amps apparently clip?
Scotty