Thread: Help with explanation of power figures

My current amplifier is the Nord One SE UP NC500DM Stereo Silver:

Specs:

550W 2ohm
700W 4ohm
400W 8ohm

My speakers are: Boenicke W11s and they need a lot of power to run them well.

I was thinking of upgrading my current Nord to MK II but am now thinking of getting the NORD ONE HYPEX SE NC1200, with specs of:

1200W 2ohm
700W 4ohm
400W 8ohm

The NC1200 has a lot more power at 2ohms.

I'm wondering if I will use the extra power that is produced at 2ohms?
The power at 4/8 ohms is exactly the same as what I currently have.

I don't understand the working of an amp and ohms etc.

The spec says that at 2ohms 1200W is produced but is that produced only at 2ohms?

Originally Posted by a.wayne

Based on the specs Posted , the Nord is best for 8 ohm nominal speakers, The NC1200 will work on both 8/4 ohm speakers and will drive high phase angles At the lower impedances.

So if your speakers are 4 ohm nominal the NC1200 is the one to have for power drive and yes the 1200 watts is for a 2 ohm load ...


Regards

BTW: Why John Atkinson Believes Measurements Matter | Stereophile.com

I started watching the video you had a link for: It looks interesting. I'll finish it at a later date.

One question: My speakers can go down to 2ohms (I don't know if that is the correct terminology?).
If I get the NC1200, does this mean that the amp will be able to produce between 700W to 1200W of power when needed?

Your Boenicke list the following:

Sensitivity: 86 – 89 dB / watt / m, depending on frequency
Nom. impedance: 6 ohms (drops to 2 ohms below 120 Hz in case loudest bass setting is chosen).

Their sensitivity & efficiency is a little on the low side - and that dip to 2 ohms in the bass frequencies possibly/probably indicates they were designed for optimal use with high current amplifiers. If EVER there was a case for that particular amp upgrade (to NC1200), your speakers are it! I'd expect a significant improvement in bass.

Originally Posted by a.wayne

Yes according to the NC1200 spec , important the amp doesn't current limit , when the impedance and phase angle changes ..


Regards

I haven't a clue if the amp current limits.

There's a review of the Signature edition here:
Nord One NC1200DM Signature Stereo Amp Review | Audio Science Review (ASR) Forum

Originally Posted by Showroom Dummies

I haven't a clue if the amp current limits.

There's a review of the Signature edition here:
Nord One NC1200DM Signature Stereo Amp Review | Audio Science Review (ASR) Forum

With the listed specs of the NC1200, it DOESN'T current limit. It is a good choice for your speakers in their "loudest bass setting" mode with that tough 2-ohm bass dip. The gold standard for "high current" solid-state amps is to double power each time load impedance halves. HOWEVER, some manufacturers will goose their specs by willingly under-listing their 8-ohm power rating just to make it "look" like their amp doubles perfectly into 4 ohms (and then 2 ohms, etc). So for example, an amp that measures 480 Watts @ 8 ohms, 200 Watts @ 4 ohms they might spec at 400 Watts @ 8 ohms, 200 Watts @ 4 ohms. Tricksey hobbitses! That said, I don't see a reason to doubt the Hypex NCore modules' numbers, they're a good company, good brand, and those NC1200 numbers look good and legit as a sweet high-current amp.

The power specifications of the Hypex class D amplifier modules into low impedance loads are limited by thermal capacity, not maximum current. Both the NC500 and NC1200 do have current limiters, but they are set at 26A and 38A respectively, so the NC1200 does have the ability to deliver more current into very low impedance loads. However, even 26A is enough to provide around 950 watts into a 2ohm load.

Most of the modest priced Hypex based designs use the same power supply for the NC500 and NC1200 based designs. I think this is bigger limitation than the maximum current capabilities of the modules themselves. It's possible that the added current capabilities of the NC1200 might have some sound quality benefits even if you are not invoking the current limiter. I have owned a Nord NC500 MkII, but have not heard the NC1200 so can't comment directly on the sound differences.

I think the bigger issue is whether you would benefit from the added thermal capabilities of the NC1200. Most of the class D amps on the market that use these Hypex modules have only modest heat sinking. In most cases, they modules are bolted directly to the bottom plate of the amp which doesn't provide much in the way of extra heat dissipation. While class D amps are very efficient, they aren't 100% efficient. As the speaker load impedance drops, the amp's efficiency drops since the current increases which must be dissipated by the output transistors based on their on-resistance, and during switching.

The Hypex amp's efficiency is about 95% into 8ohms, but only about 88% into 2 ohms. So if you are putting 1000 watts into the speaker at 2ohms, the amp has to dissipate 120 watts. This is a huge amount for the small plates the amp modules are mounted on and the thin amplifier base plate. Consider the size of the heatsinks in the FirstWatt amplifiers, which dissipate about the same power (a bit more for some models). So high power demands can quickly push the amplifier into thermal overload.

Fortunately, when we are listening to real music, the vast majority of the time, the amp is only generated a tiny amount of power. I don't listen super loud and my speakers are a bit more efficient (92db/w), and when I'm listening, my amp is putting out less than a watt most of the time. I have to really crank them to get peaks over 100 watts (based on my measurements).

Bottom line, both of these amps have exceptionally low output impedance (and thus very high damping factor). I doubt you will notice a significant difference in sound quality unless you are exceeding the amps thermal capabilities. These modules do incorporate some soft-clipping features to try to prevent overload when the amp is being pushed. So if you are really pushing it hard, this would have an effect on sound quality.

Mmmm, not sure what to do now.
Upgrade my current amp to MKII or get the NC1200, or stick with what I have?

@JayT: If you don't think my speakers will use much, if any of the 1200 watts then perhaps it's not worth getting?

The problem is is that I don't understand how a amplifier interacts with a speaker and what it means when a speaker enters 2ohms and how that affects the working of the amplifier etc.
With Class D, how it works is most probably different to how other amps work? I don't know.
I know Class D produces its power differently and that's all I know.
Could someone (for instance) give me information about how the NC1200 amplifier would work with my speakers but this is based on Class A/B, which is not the same way a Class D works?

I need help from members who understand these technical details so I make a decision.

The only way I will know if the NC1200 is better will be to try it, but that means ordering one.

I suggest giving Colin a call at Nord at get his recommendation. Since you live less than a couple hours away from Nord's headquarters, he may be willing to let you borrow a demo NC1200 amp and/or new buffer boards for your NC500s to try out. If not, Nord has a 14 day return policy, although I think that is too short to get a good idea, particularly with the longish break-in of these amps, but you'd get an idea of whether the extra current capability of the NC1200 makes a difference.

Get the NC1200 amp if you want more oomph and impact from your speakers. You should hear a difference in the bass even if you don't use anywhere near its max Wattage. If those speakers were designed for high current amps, and going by specs it looks like they were (it's almost a sadistic load), then they might sound relatively anemic without one - regardless of your chosen volume level. If anything I'd ask the Boenicke people for further advice on this matter. But yeah if you can get a loaner NC1200 from Nord to try - problem solved! Your ears on your own system are always the best discriminator.