Review and Measurements of Nord One NC500 Amp

[Samoyed]

Somewhere, in the forest, a tree fell....

 

[Bamyasi]

Now I'm just a bit worried about any potential problem using XLR to RCA cables(my Arcam only has RCA out). Anything to think about here?

(output) RCA -> XLR (input) should be fine; the opposite way (XLR->RCA) is NOT fine most of the time. Always check the actual wiring for the cables/adapters you buy.

 

[restorer-john]

The unit is not made for continuous power at max wattage.

And here we go again.

Hypex watts are essentially the New Millennium Versions of Peak Music Power watts of last century.

At least run it for 5 minutes at 100W (its 'real' rated power) as a bare minimum. If it blows up or shuts-down, it's a genuinely faulty design and should be exposed as such.

 

[Samoyed]

I don’t care if it spits fire out of its ass, it sounds wonderful.

 

[levimax]

No this is completely wrong. Class d does not get a free pass. Ultrasonic distortion is not just unheard, it's simply not reproduced. It's called putting it into context. You need to come up with a cogent argument as to why it's a problem.

Your example above is completely erroneous.

u
Here is my point, if I have the choice between two amps, both -100 db 20 Hz to 20KHz but one has -10db @ 450 KHz (which is not a trivial amount of energy whether you can hear it directly or not) and the other has no ultra sonic distortion, I will take the one with less distortion. More distortion is never better than less and more RF especially is never better than less. Wi-Fi some how gets picked by my TT and that is much higher frequency than 450 KHz and it is very difficult to prevent. I hope some day they figure out how to prevent all the ultra sonic distortion / noise in class D but until they do, based on objective measurements, you have to conclude a well executed non switching amp out performs the current class D amps.

 

[amirm]

At least run it for 5 minutes at 100W (its 'real' rated power) as a bare minimum. If it blows up or shuts-down, it's a genuinely faulty design and should be exposed as such.

Given that the seller is in UK, getting it repaired/replaced would be quite onerous. So I can't make that decision on my own.

 

[restorer-john]

Left channel might be noisier because it is the channel with the SMPS with the heatsink facing out, while the right channel has the SMPS heatsink facing in.

And look at the superb placement of the mains wiring and chokes right up against the module itself.

 

[LTig]

And here we go again.

Hypex watts are essentially the New Millennium Versions of Peak Music Power watts of last century.

At least run it for 5 minutes at 100W (its 'real' rated power) as a bare minimum. If it blows up or shuts-down, it's a genuinely faulty design and should be exposed as such.

I don't share your harsh critic. The difference between peak power and average power in music is quite large - even on recordings suffering heavily from the loudness war there are at least 6 dB of dynamic range. This is a factor of 4 regarding power. A power amp with 100 W continuous power and 400 W peak power is not faulty but perfectly suited to the task of audio play back. It must be able to deliver the peak power for at least a few seconds, of course (not like those infamous 1000 W PMPO PC speakers with a 5 cm bass chassis which delivered 1000 W power only once in their lifetime - when being burned).

The famous NAD 2200 stereo power amp (still have 2 in stock) had just the same specs (100 W continuous, 400 W peak). There is a video at youtube where someone measures its power and he was able to get 1800 W into 4 Ohm in bridged mode:

 

[restorer-john]

No this is completely wrong. Class d does not get a free pass. The switching frequency is not just unheard, it's simply not reproduced. It's called putting it into context. You need to come up with a cogent argument as to why it's a problem.

OK, put it this way. Do you think that an Audio Amplifier should reproduce or emit anything other than an amplified, un-distorted version of the original signal and absolutely nothing else?

Many Class Ds wipe out AM radio reception and render shortwave unlistenable. Many Class D chips offer variable carrier adj taps so when installed in or near a tuner board, the tuner board actually partially works.

Class D as a whole is attempting to control the message (unsuccessfully IMO) that spurious RF/EMI at high levels is not a problem, when previous to its implementation, any noise, any spurious tones, any un-correlated EMI/RFI was indicative of a faulty design.

 

[restorer-john]

The famous NAD 2200 stereo power amp (still have 2 in stock) had just the same specs (100 W continuous, 400 W peak). There is a video at youtube where someone measures its power and he was able to get 1800 W into 4 Ohm in bridged mode:

The only thing 'famous' about the 2200 'The Powertracker' was its frequency of failure. I've lost count of the number of those I've either fixed or written off.

It was a hurried design, prone to spectacular failure. That said, when it worked, it worked quite well. It was a 100W amp that could hit silly figures for a short time, that's all. But it was sold to people as a wolf in sheep's clothing which it wasn't. People who couldn't afford a real 400+400W amp would buy them for their big JBLs and push them. They blew up often.

This peak vs continuous argument was settled decades ago, all the manufacturers went back to non-commuating rails and plenty of SOA in silicon. Look at the Benchmark- that's a conservative output stage.

PS. If you like the commutating rail power amplifiers, look at one of the very first that actually sounded good, the Hitachi HMA-8300 from 1977. 24kg (twice the NADs weight), 200W/ch@8 and a short term rated 400W, (measured) over 500W/ch. It was built like a tank, but still, they go up like fireworks when things get hairy. I've got one in my storeroom. In my estimation, it has about half the number of output devices it needs...

(internet pic)

 

[LTig]

The only thing 'famous' about the 2200 'The Powertracker' was its frequency of failure. I've lost count of the number of those I've either fixed or written off.

It was a hurried design, prone to spectacular failure. That said, when it worked, it worked quite well. It was a 100W amp that could hit silly figures for a short time, that's all. But it was sold to people as a wolf in sheep's clothing which it wasn't. People who couldn't afford a real 400+400W amp would buy them for their big JBLs and push them. They blew up often.

In the company I work for we used the NAD2200 as amplifiers for gradient coils in micro MRI tomographs. The input stage was modified to handle DC and nulling the DC offset. I got two of those amps after they came back from a customer after many years of faithful service. I undid the modifications and both amps were working, except that one output relay hung up (always on, maybe due to feeding an inductive load?). I have to check with some of my older colleagues, maybe someone remembers how often they failed.

BTW, do you know a source where I can get those output relays?

 

[Samoyed]

Given that the seller is in UK, getting it repaired/replaced would be quite onerous. So I can't make that decision on my own.

He has a repair source in the U.S.

 

[restorer-john]

BTW, do you know a source where I can get those output relays?

These can be used (attached pdf)

Trim R413 to suit after measuring the applied on voltage- the two relay coils are in series.

 

[LTig]

These can be used (attached pdf)

Trim R413 to suit after measuring the applied on voltage- the two relay coils are in series.

Thanks. SInce I have only a copy of a copy of a copy of the schematics which is very hard to decipher, may I ask some questions:

• Is the SRK pin compatible?
• Which voltage version do I need (6/12/24V)?
• Or do you have the order code available?

 

[restorer-john]

may I ask some questions:

Just PM me.

 

[D700]

Apollon NC800SL
Picture optimized

View attachment 27068


Nord One NC500 Amp

The choice is evident to me.

From photo, the leads to speaker terminals on Apollon use same red color for positive and negative. Wouldn’t that invite same out of phase problem Amirm found on the Nord?

Neither of these photos are inspiring to this layperson.

 

[Xulonn]

Hypex watts are essentially the New Millennium Versions of Peak Music Power watts of last century.

Don't forget Bob Carver's "Magnetic Field" (switching power supply) amplifiers. I think I told the story here of how my "200wpc" Carver M400t Cube amplifier (driving a pair of ADS-L810 speakers) went into thermal shutdown during a party at my house with a lot of people in the room. Poor headroom and/or reserve power, but for most people and normal listening, apparently that was not an issue. Indeed, at sites like Audioreview.com, as "vintage" amps, they still have lots of fanboys.

 

[orangejello]

Another alternative would be a used NAD M22 v2. They have NC400 modules, a custom power supply an input buffer, three different gain settings, and switch on and off depending on the presence or absence of a signal. They also have a trigger. They are available for around 1500-1600 on the used market. The case makes the Nord and other builds look rather shabby. Their QA is probably a lot better.

 

[invaderzim]

And look at the superb placement of the mains wiring and chokes right up against the module itself.

View attachment 27078

It looks like they had plenty of room to set it up better

 

[cjfrbw]

So one of the charms of class D is the very high transient peak power over RMS power? I didn't know that they are rated by 'peak transient power' rather than RMS.

In the olden days, many amplifiers had figures for both RMS and peak, with the peak being from 0db to 1db to upwards of 5db ( with some push pull class A types going into class B).

I suppose that's good for music signals and efficiency, but also why Class D might not be all that for ruggedness.