[Cielspacing]

Power efficient, lightweight, ultra Hifi, reasonable prices...
And now V2.

Sure plenty of people would be happy to see this line of evolution.
At my case, part of my audio life is related to Electroacustic music and mobile events, visit http://www.cech.cl/.
And for a whole audio area that means 8.0 as our worldwide standard, highly dynamic, low noise, high resolution, mobile ...sound systems.

First time I found about Nuforce, it all sounded almost too perfect to be true. Every specification -as explained in the website- was close to what we need and so this tech appreared as the still elusive answer to an important part of the implementation of our ongoing audio quest.   
Until I found about the Nuforce "open loop" particularity and the implied risk of amp failure if they are powered up while unconnected to the speakers.
Inmediatly several actual situations came to mind where somebody tripped and disconnected a cable (of the complex in situ set up) or the "live" failure of a particular driver,etc,etc.
That ghost was enough for me to let this solution aside and wait for future developments.

Now V2 is released and some time has past thus maybe some solution/change has been implented

In case this very same issue was already discussed, I've done a thread by thread search back into 2006 and alternatively attempted a forum search (with the Nuforce area selected) both dilligences with no results.

I'll apreciate an update on this matter and -even better- I'd prefer a hope of future solution rather than a dry, negative answer.
Thanks

 

[rustydoglim]

We have not encountered a single incident (not failure) of overheating without speaker load. Well, with more than 600 V2 units (upgrade and new) already out there, I would say it is pretty safe that the amp will be fine with the speaker load removed accidentally.

Just in case the amp overheats due to no load condition, it will shutdown for protection. And it takes 10 to 15 minute to cool down and a power off/on reset to restart it. In our lab, we intentionally overheat it with continuous high power (part of our QA process) to test the reliability of the amp.

At this point, we still think it is best to recommend that the amp be powered on (or use) with speaker load connected.

[nuforce-casey]

Until I found about the Nuforce "open loop" particularity and the implied risk of amp failure if they are powered up while unconnected to the speakers.

The basis of 'self oscillating amp' requires a closed loop for the amplifier to properly function, and in V2 version, there is a zobel filter (i.e. a virtual load) to maintain closed loop in case the speaker gets disconnected under accidental scenario.

We put in 'safe guards' as safe guards, not as a feature.  Just like the Airbags in your car are never intended so you can drive without wearing seat belts.....  It is not true that you will see spectacular fire work the moment you turn-on Nuforce without speakers connected - but we do want you to immediately rectify the situation before continuing further.  Other tendency is a loose speaker cable connection typically shorts the terminals and a short circuit is much worse than open-load to the amplifier.

Nevertheless, Nuforce amp should never be operated without speakers and this factory disclaimer and exclamation should stay (why do you turn-on an amplifier without connecting the speakers?)  It's just common sense and good practice anyway, not particular with Nuforce or switching amplifiers.

As a matter of fact, I have 20 years experience with electronic component, I do not recall a single instance that I switch speakers or cables without first powering down the amplifiers (tube, Class A/B, Nuforce, etc). 

[Cielspacing]

Just in case the amp overheats due to no load condition, it will shutdown for protection

That's just what I wanted to hear, Jason.
So I can conclude that -at V2 case- whatever speaker load/unload situation, the worst thing that could happen is that the power switches off and no damage is done.
Good news indeed.

Additionally the fact that

in V2 version, there is a zobel filter (i.e. a virtual load) to maintain closed loop in case the speaker gets disconnected under accidental scenario.

could possibly ease a way to monitor the accidental condition, ie a red led switches on together with the zobel filter activation.

I mention this small detail because at complex mobile amplification systems, there is always a good way to monitor the presence of signal way up to the crossovers or digital speaker management units, but from there on (amps to speakers) there is little cue apart from the audition itself... something that with 8.0 multiamped systems could be increasingly difficult to discern.

Thank you for your answer and for bringing up solutions to a varied customer base.
Nacho

[rustydoglim]

ie a red led switches on together with the zobel filter activation.
I mention this small detail because at complex mobile amplification systems, there is always a good way to monitor the presence of signal way up to the crossovers or digital speaker management units, but from there on (amps to speakers) there is little cue apart from the audition itself... something that with 8.0 multiamped systems could be increasingly difficult to discern.

The Ref series are designed for ultimate raw performance so we don't want to add anything to reduce performance.  Stay tune for the multi-channel amp series. It will have remote on/off for each channel, LED indicator, trigger in etc. The ultimate audiophile home theater system would be to combine Ref series monoblocks with multichannel amp.

[Cielspacing]

Since the Zobel activation happens only when when the loop opens (or the temperature raises over certain level?), the led activation(or changing color) could possibly be a derivative line, which wont be altering normal performance, me thinks.

And yes, the idea is monoblocks on multichannel amps, thus typical electroacustic system is 8.0, for simplicity reasons usually utilise common active one-way boxes, but ideally it will be on two-way speakers, which means 16 monoblocks, or even better done in three-way, but this means 24 monoblocks plus plenty of cabling,etc...

Hence easy, unobstrusive monitoring is very desirable. Apart from the 4 adjetives written as the first 4 words in this thread.
That is why Nuforce technology looks as a new -recent- solution.
 

[nuforce-casey]

Our new multichannel amp will offer monitoring and self-diagnostic.

[stingfan]

Just thought I'd add an incident that is partially related to this thread.  The other day we had a major power outage in San Francisco, http://www.pge.com/news/news_releases/q3_2005/050824a.html, which caused power in my loft to come on and off 5 times in the span of 30 minutes.  I was at work, but my wife was home that day, and heard the 9SE V2's turning on and off with the power. (I leave my amps on continuously, and plugged directly into my sockets as I have very clean power here)  They were making a power up thumping noise because after the first outage, my P-8 preamp drops into the off/standby mode, and the amps don't like to be turned on before the P-8.  So after the incident, I had my wife power down the V2's.  When I got home, I properly turned up the system again, no loud thumping, nice and quiet, and we were back in business.  No issues, no problems with the speakers, or the amps. 

Just wanted to share this story that the Nuforce gear can handle some pretty dicey power up situations with no damage to themselves nor to other the components in your system. 

[JayDoubleU]

This is exactly my concern: we had some power outages recently. P8 would come back to standby afterwards, ref 9 would be powered fully. If nobody is home to rock the switches, what would happen to Ref9? It might be switched on without input load from P8 for up to 10 hours. Will Ref9 switch off and be safe, or do I risk losing a great set of amps?

[rustydoglim]

This is exactly my concern: we had some power outages recently. P8 would come back to standby afterwards, ref 9 would be powered fully. If nobody is home to rock the switches, what would happen to Ref9? It might be switched on without input load from P8 for up to 10 hours. Will Ref9 switch off and be safe, or do I risk losing a great set of amps?

Ref 9 should be safe in the above situation.  If you're worry about frequent power outages, you should leave the equipment power off.