[jmdesignz2]

Anyone have things to say about Hypex nc400 ncores with 4 to 3 ohm speaker loads?

My speakers are 86db efficiency, aerial 10t. Wondering if the ncores nc400 would be better than my current mccormack dna1 dlx monoblocks?

[cab]

ncore is fine down to 2 ohm loads so you should be fine.

[Julf]

ncore is fine down to 2 ohm loads so you should be fine.

Yes, absolute minimum load is specified as 1 ohm. My experience is that they are great at driving really tricky and complex loads.

[titaniumheads]

I have been using a pair of Nc400s on a pair of Magnepan 3.7s recently and at high dB levels they shut down. I have not been able to find anything about this on the forums
If I shut them off and turn them back on in about 10 minutes they work fine. Is there some type of circuit breaker in the NC400 that resets?

[Atlplasma]

I have been using a pair of Nc400s on a pair of Magnepan 3.7s recently and at high dB levels they shut down. I have not been able to find anything about this on the forums
If I shut them off and turn them back on in about 10 minutes they work fine. Is there some type of circuit breaker in the NC400 that resets?

They may be overheating. What happens when you remove the enclosure cover and/or point a fan at the amps when under heavy loads?

[titaniumheads]

I have not tried that, they are in aluminati cases with plenty of room around them. I bought them used from a member here. I keep hearing how great they work with Maggies but I am guessing
others are not pushing them very hard. I know in our audiophile club when levels hit 90DB everyone yells, turn it down, turn it down.

[mikeeastman]

I had a similar problem with one of my nc400 mono blocks and it turned out that the A/C input wires were reversed, switched them back and it worked fine since.

[a.wayne]

I have been using a pair of Nc400s on a pair of Magnepan 3.7s recently and at high dB levels they shut down. I have not been able to find anything about this on the forums
If I shut them off and turn them back on in about 10 minutes they work fine. Is there some type of circuit breaker in the NC400 that resets?

Sounds like a temperature issue ............

[Julf]

Sounds like a temperature issue ............

I agree. I suggest measuring the temperature of the nc400's and the smps's when the cutoff happens.

[Julf]

I had a similar problem with one of my nc400 mono blocks and it turned out that the A/C input wires were reversed, switched them back and it worked fine since.

The A/C wires have no intrinsic polarity. There is no "correct" and "reversed" direction. It sounds like you had earth/ground issues.

[mikeeastman]

Julf, that had always been my understanding also, but all I know is when I switch the wire on the smps  that was shutting down, it stop shutting down and has work fine since. 

[jtwrace]

Maybe tiheads can post a picture of the IEC so we can see how it's wired.  If it's "reversed" he can change it since it's so simple and a good place to start. 

[Julf]

Julf, that had always been my understanding also, but all I know is when I switch the wire on the smps  that was shutting down, it stop shutting down and has work fine since. 

Is your power cable a 2-pole or 3-pole one? Is the chassis earthed?

[Julf]

Maybe tiheads can post a picture of the IEC so we can see how it's wired.  If it's "reversed" he can change it since it's so simple and a good place to start.

But how do you know which way is "reversed" and which isn't ?

[poseidonsvoice]

I have been using a pair of Nc400s on a pair of Magnepan 3.7s recently and at high dB levels they shut down. I have not been able to find anything about this on the forums
If I shut them off and turn them back on in about 10 minutes they work fine. Is there some type of circuit breaker in the NC400 that resets?

From the Magnepan website (FAQ section):

A new type of amplifier (Class D) has become more popular because it is a "green" design and uses less power plus it is smaller in size compared to conventional amplifier designs. We have heard reports of Class D amplifiers shutting down when driving 4 ohm loads or sound quality that is less-than-desirable. Quite frankly, some sound very poor on Maggies. However, more recent designs of high-end models are much better. Because we do not have the time to determine which models of Class D designs are compatible with Maggies, we must take a conservative approach. Direct-coupled, Class A/B designs with high current capability have proven a good choice for many decades.

So that was some funny reading at least for me 

So titaniumheads, I am curious. What is high dB levels to you? Are you using an SPL meter and if so, what level is it when your amp shuts down (measured from your listening position)? How far are you from each Magnepan 3.7 (please measure accurately!). What is the cubic feet of your listening room, or alternatively the LXWXH in feet?

Judging from the spec sheet on the NC400, and knowing that your NC400 is mounted in the incredible Aluminati cases, they should be getting enough heatsinking if built properly and as long as there is heatsink compound between the NC400 and the chassis (I am going to assume so).

The spec sheet on the NC400 and the graphs seem to suggest that 400-500 watts at 4 and 3 ohm loads is really about the limit for this amplifier. They don't give a max specification, just a typical specification. And the graphs seem to agree with this. Yes, the NC400 can put out gobs of current.

The Magnepan 3.6 is a pretty resistive load of 3 to 4 ohms judging by the last Stereophile review. I haven't seen any accurate, repeatable and verifiable measurements on the 3.7. I'm going to hazard a guess that it will also be about 3 to 4 ohms, and the sensitivity is really 83.5 to 84dB at 2.83V input (at around 500Hz). So if you are seated about 10 feet from each speaker (and I know the speaker is a QUASI line source), then you will achieve about 107dB PEAK, at the listening position, at 400-500 watts; this might be an instantaneous output since the average spl might be about 10-15 dB lower, i.e. 90dB (depending on how compressed your particular song you are playing is, how much bass content there is, etc...).

There are a lot of SPL calculators on the internet. However, the one I found to be the closest to real world simulation is this one (make sure you state that the speakers are IN phase):

http://www.doctorproaudio.com/doctor/calculadores_en.htm#calc_spl

If you find that your NC400 build is not suspect, ie. everything is wired correctly and there is plenty of cooling provided by the Aluminati case, then there are only a few options.

Turn the volume down   .
Get more sensitive speakers 
Get a larger amplifier 
Move closer to your speakers 

FWIW.

Thanks,
Anand.

[Julf]

The spec sheet on the NC400 and the graphs seem to suggest that 400-500 watts at 4 and 3 ohm loads is really about the limit for this amplifier. They don't give a max specification, just a typical specification. And the graphs seem to agree with this. Yes, the NC400 can put out gobs of current.

The Hypex specs are pretty clear. The SMPS600 data sheet specifies 575W@120Vac/550W@230Vac into 4 ohm for 90 seconds, 430/400W for 5 minutes and 275/240 continuous.
The NC400 data sheet specifies a 24A output current limit and a minimum load impedance of 1 ohm.

Most importantly, exceeding the output current /output impedance only leads to limited output power, not shutdown.
The shutdown is caused my something else - DC offset, temperature too high or supply voltages out of spec.

Titaniumheads, is there any possibility that nAMPON might be floating or not pulled down strongly enough? Are you using the standard SMPS600 without any external mains filters?






         

[poseidonsvoice]

The Hypex specs are pretty clear. The SMPS600 data sheet specifies 575W@120Vac/550W@230Vac into 4 ohm for 90 seconds, 430/400W for 5 minutes and 275/240 continuous.
The NC400 data sheet specifies a 24A output current limit and a minimum load impedance of 1 ohm.

Most importantly, exceeding the output current /output impedance only leads to limited output power, not shutdown.
The shutdown is caused my something else - DC offset, temperature too high or supply voltages out of spec.

Titaniumheads, is there any possibility that nAMPON might be floating or not pulled down strongly enough? Are you using the standard SMPS600 without any external mains filters?
       

Ok. Thanks for stating that! Hopefully it's a DC offset issue or supply voltages are wrong.

I guess he can keep cranking the volume control for extended periods, it just shouldn't play as loud but not shutdown.

Best,
Anand.

[greenkiwi]

I'm guessing that unless @titaniumheads has changed anything:

1. the grounds are all tied to the chassis/earth ground
2. the power supply is the standard SMPS600
3. the nAMPON is just jumpered to ground

Because I believe that is how KD had set them up.  Assuming they weren't changed along the way.  But always good to check.

[a.wayne]

A friends  class -D Rotel does the same thing on his ML , the NC400 is shutting down due to its inability to sink the large current necessary for sustained listening on the maggies , you have to use fans or put much larger heat sinks, its easy to test with a 4 ohm dummy load and or has anyone SEEN Any FTC preconditioning test done on an NC400 , how it performs there will tell the tale ........


Regards

[Julf]

A friends  class -D Rotel does the same thing on his ML , the NC400 is shutting down due to its inability to sink the large current necessary for sustained listening on the maggies , you have to use fans or put much larger heat sinks, its easy to test with a 4 ohm dummy load and or has anyone SEEN Any FTC preconditioning test done on an NC400 , how it performs there will tell the tale ........

Should be easy to verify by checking how hot the nc400 gets. It might possibly be an issue in a totally closed enclosure with no air flow whatsoever, but I doubt it...