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Review and Measurements of Nord One NC500 Amp

Possible with a DAC is connected direct to power amp?

Especially DAC's that up-sample to high sample rates? Many up-sample to 384kHz and above these days, before converting to analogue?

Yes, we had this discussion elsewhere (DSD thread). However that other signal has to be of significant amplitude to get translated into audible levels in the normal range.

An audio amplifier that is open to 380kHz is a *BAD* design. It will be prone to RF interference from other sources. It should have an input filter.
 
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So, the switching noise, it's a constant. What voltage is it in absolute terms? Nano? Milli? Kilo?

Hypex NC252MP module with no speaker connected. About 350mV rms. This has no impact on tweeters, the power levels are too low (remember crossovers and the tweeters inductive reactance means its is not an 8 or 4 ohm load)

scope_0.png


The switching signal is not constant, it is modulated by the audio signal. Below is with my finger on the input connector (50Hz).

When the switching signal is removed by the low pass filtering of the speaker, all that is left is the audio range signal.

scope_2.png
 
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Hypex NC252MP module with no speaker connected. About 350mV rms. This has no impact on tweeters, the power levels are too low (remember crossovers and the tweeters inductive reactance measnd its is not an 8 or 4 ohm load)

View attachment 27061

The switching frequency is not constant, it is modulated by the audio signal. Below is with my finger on the input connector (50Hz).

When the switching signal is removed by the low pass filtering of the speaker, all that is left is the audio range signal.

View attachment 27063


Nice. Are you sending one of your power amps to amir for measurements? Soon?
 
In my amplifier, the amplitude of the switching frequency is about 620 mVp-p. I don't know the sound quality is accurately transfered to you on youtube, but the sound quality is excellnt.


I was just thinking of tweeters maybe heating up due to the dissipation of that HF power, but at 220mVRMS it's negligibly low.
 
I was just thinking of tweeters maybe heating up due to the dissipation of that HF power, but at 220mVRMS it's negligibly low.

That's what the screenshot I shared above is talking about too - blue'ed voice coils.
 
Nice. Are you sending one of your power amps to amir for measurements? Soon?

I am sending a P252 and a P701 (Hypex Ncore NC1200 module) to Amir, but my understanding is there will not be a formal review, just testing data which I can present.
 
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That's what the screenshot I shared above is talking about too - blue'ed voice coils.

Bad amp design. A/B amps can fall into oscillation at high frequencies with even more spectacular results.
 
That's what the screenshot I shared above is talking about too - blue'ed voice coils.

Lets do the maths (I hate this as I am somewhat mathematically inept so please check the numbers :) )

Just went to Madisound and at random picked a Scanspeak D2604 tweeter. It parameters are below.

1559367902226.png


So we want to calculate the power dissipated by the tweeter caused by the switching frequency. First we need to calculate the impedance of the coil at the switching frequency. We will use 400kHz. We will ignore a few things but it will be ballpark.

Impedance Z = 2 * Pi * F * L

Z= 2*3.14*400000*0.00002
Z= 50.24
+R = 53.14 ohms

This value is ignoring the effect of any speaker cabling or crossover in circuit which will increase the impedance further.

So current = V / Z
I=0.35 / 53.14
I= 0.0066 A
I=6.6mA

Power = V * I
P=0.35*0.0066
P= 0.0023 W RMS

Power dissipated by the coil = 23 mW RMS

A total non issue, and this is in a directly connected scenerio without a crossover circuit or speaker cables.

Look, I have no doubt a bad class D amp somewhere has fried a tweeter, but in properly designed amps its not a problem.
 
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I was a bit unhappy about the channel in blue which seemed to dance around with those extra spikes. The levels are low but not nice engineering.

Maybe is the left channel? The right channel has the heatsink as a shield for the Hypex buffer.

Oh, Matias said the same!
 
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Personally, after much consideration I've decided to go for Apollon NC800SL, which is currently awaiting to be put on the plane in Ljubljana on its way to me, so my interest in the Nord amplifiers is more academic at this point.


Apollon NC800SL
Picture optimized

Apollon-Audio-Hypex-Nc500-based-Amplifier-top.jpg



Nord One NC500 Amp

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The choice is evident to me.
 
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I had a Nord One UP NC500DM for about a year, after buying secondhand. It seemed fine audibly but was quite warm to the touch and had an annoying habit of getting the power on/off button stuck. The only solution to the latter was unscrewing the top and jiggling it around, which got to be a pain.
Colin at Nord One is a nice guy and very helpful. Has several opamp options etc for those so inclined, but pushes it very gently.
Ultimately I replaced it with an integrated amp, partly due to the ergonomic issues noted above. Based on Amir’s tests I’d look at diying if I went Hypex again.
 
Apollon of course!!! I can see a good engineering inside.

Although Hypex boasts that its SMPS emits very little, it is never too much to take advantage of the aluminum heatsink as a shield for audio electronics.

And then there is the wiring.

The perforation of the base will facilitate cooling.

And the person in charge knows very well what he has in hand. He is supercommunicative.

Mocenigo, with whom I have been in contact for a few years, also bought that Apollon after discarding other implementations, as well as those based on the IcePower 1200AS2. With Audio Note speakers, high sensitivity.
 
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Hypex NC252MP module with no speaker connected. [..]

The switching signal is not constant, it is modulated by the audio signal. Below is with my finger on the input connector (50Hz).

When the switching signal is removed by the low pass filtering of the speaker, all that is left is the audio range signal.

View attachment 27063
I don't think that the shaded area around the sinus signal is RF. It's just the area which the sinus covers riding on the 50/60 Hz mains frequency, added by your body acting as an antenna. Trigger the scope with the mains frequency and using a sufficient horizontal time will show it.

And the speaker does not really filter RF, it transforms it into heat dissipated by the speaker coil (and parts of the crossover).
 
I don't think that the shaded area around the sinus signal is RF. It's just the area which the sinus covers riding on the 50/60 Hz mains frequency, added by your body acting as an antenna. Trigger the scope with the mains frequency and using a sufficient horizontal time will show it.

And the speaker does not really filter RF, it transforms it into heat dissipated by the speaker coil (and parts of the crossover).
I wasn't aware that I said it was. It's the audio signal modulation. I was injecting a 50Hz audio signal to demonstrate the modulation. Entirely intentional and quicker than hooking up a sig gen.

I mentioned the power dissapation which will run to heat (the resistive part)

No it absolutely does filter the 400kHz signal. It is incapable of turning that into kinetic (acoustic) energy.

You put the signal in and nothing comes out. Not sure what your definition of filtering is but it fits mine in this context.
 
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I wasn't aware that I said it was. It's the audio signal modulation. I was injecting a 50Hz audio signal to demonstrate the modulation. Entirely intentional and quicker than hooking up a sig gen.

I mentioned the power dissapation which will run to heat (the resistive part)

No it absolutely does filter the 400kHz signal. It is incapable of turning that into kinetic (acoustic) energy.

You put the signal in and nothing comes out. Not sure what your definition of filtering is but it fits mine in this context.

Wouldn't it generate heat in the tweeter putting a stress on it that a class AB amp would not?
 
I have to say after thinking about pulling the trigger on a Nord amp for a couple of years now I'm quite put off by the result of this test. First of all I'm not about to open up a new amp to check if it's wired correctly. That's almost the most off-putting since if a simple thing like that is missed there can't be a QA process in place. Who knows what other types of issues one can run into.

Then there is the measurements of the amp. I guess they're not terrible but I expected way more to be honest. Now the NC400 kit looks way more appealing now but I'm not sure the power is enough for my needs. Then there is the high frequency stuff which there doesn't seem to be a consensus about if it negatively affects the lifespan of the tweeter. It's been mentioned that well engineered class D shouldn't be a problem but which ones are well engineered? How would you know this, or could this type of issue arise in class AB as well? My tweeters are quite expensive so taking no chances there. I guess my search continues.
 
Now the NC400 kit looks way more appealing now but I'm not sure the power is enough for my needs.
Who needs more than 400W into 4ohm?

Despite advertised amp power specs, most speakers can’t handle more than 150W into 8ohm, many can’t even handle 100W. Power recommendation specs are meaningless and are different than wattage handling specs.
 
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