Buckeye NC252MP Stereo Amplifier Review

[sigbergaudio]

Whether it is 16 or 20 Hz - does not matter in the end - the power must be stable over a long time.

But it is stable over a long time. We use them in subwoofers for heavens sake. And we're not the only manufacturer to do so. I'd upload a video of a slow sweep starting at 10hz but apparently I'm not allowed to upload video files. And I guess someone would still find a way to go "Yes, but what if.."

 

[Sokel]

But it is stable over a long time. We use them in subwoofers for heavens sake. And we're not the only manufacturer to do so. I'd upload a video of a slow sweep starting at 10hz but apparently I'm not allowed to upload video files. And I guess someone would still find a way to go "Yes, but what if.."

You know better the "what if".
A lowpassed sub will playback it's range just fine I guess,energy very low is limited (in time at least),etc.

But if an amp is used fullrange all that will combine with the main bulk of energy which is in the midbass (yes,where we see the most problems with integration) so it's a whole new ball game.
That's the reason actives are way ahead,we don't want to get to that debate.

In a technical review the most important thing is that the device follows it's specs.
Use cases are chaotic and one can choose accordingly.

 

[chris256]

But it is stable

If it's quite enough, surely, no doubt. But not if it's really loud and if the speakers are demanding. Amir's test tells the opposite. The job of tests is to reveal the limits. Because customer wants to see them. Btw: Amir's tests regarding power amps are much too good-natured. They should be much more demanding, more real life oriented.

Use cases are chaotic and one can choose accordingly.

True - but you can choose the easiest ones or the more demanding. Goal is to choose the most demanding, because all others will work afterwards. I'm not interested in easy use cases - I'm interested in the edge cases!

 

[peng]

Ok, 20 ms or a bit more or less - it's just a joke. All these synthetic sweeps are far from reality. Just one example: take an organ pipe / 32 ft: it produces a ~16 Hz tone - not just for a few ms but for a long time. See the final sequence here as just one example. Start at 40:49 or go directly to the final chord (41:10 - 41:21). 11 s (!!) ~16 Hz. That's the challenge which has to work stable without any restrictions on high volume (I want to feel it, too).

I picked 20 ms to make a point, I don't know how long the amp can play a 20 Hz tone for. If I want to listen to those pipe organs at loud spl, without using powered subwoofers, I would look to much more powerful amps, assuming I have the speakers that can do the job.

 

[sigbergaudio]

In a technical review the most important thing is that the device follows it's specs.
Use cases are chaotic and one can choose accordingly.

We still don't know if it follows its specs based on this test, as we don't fully understand the test that has been carried out.

My problem isn't really with it failing the test. I'm not claiming it's impossible to make the amp go into protection, Amir has already done that in his test. What I have a problem with, both here specifically and more in general, is people making assumptions and jumping to conclusions and misreading the data that is presented.

Focus on high quality engineering is awesome. Being curious about anomalies is also fine, and interesting. But there should be at least some perspective. This is in all fairness a pretty reasonably priced amp, that will do an excellent job in almost any scenario it will reasonably be tasked to handle. Shouldn't that be the main focus?

Sometimes on this forum it sounds like any amp with less than 100dB SINAD isn't even worthy of powering a clock radio.

 

[sigbergaudio]

If it's quite enough, surely, no doubt. But not if it's really loud and if the speakers are demanding. Amir's test tells the opposite. The job of tests is to reveal the limits. Because customer wants to see them. Btw: Amir's tests regarding power amps are much too good-natured. They should be much more demanding, more real life oriented.

If the tests make an amplifier fail something it wouldn't fail in real life, I can agree that it should be more real life oriented, but not necessarily that it should be more demanding.

 

[sigbergaudio]

Ok, 20 ms or a bit more or less - it's just a joke. All these synthetic sweeps are far from reality. Just one example: take an organ pipe / 32 ft: it produces a ~16 Hz tone - not just for a few ms but for a long time. See the final sequence here as just one example. Start at 40:49 or go directly to the final chord (41:10 - 41:21). 11 s (!!) ~16 Hz. That's the challenge which has to work stable without any restrictions on high volume (I want to feel it, too).

And your speakers are 2 ohm or less at 16hz?

 

[Sokel]

ain focus?

Sometimes on this forum it sounds like any amp with less than 100dB SINAD isn't even worthy of powering a clock radio.

I'm not in that group by all means,to me power amps are about power,they must deliver under any demand and circumstances they rated specs.
As long as I don't hear any noise or some enormous distortion I'm more than ok.

 

[squared80]

Nice performance, pedestrian design.

Which leads to the price point. My Buckeye amps are locked away in my equipment rack, which I never see, so they're perfect for me. But you can get any color you want.

 

[Rick Sykora]

Regarding the 2ohm resistive load test, it should be pointed out that another NC252MP (not ours) failed it as well previously.
Not shifting the blame or brushing it off. But more so lending credence to those who have suggested there may be a difference between the conditions when Hypex specs the 2ohm performance vs. Amir’s test.

Since you are being nice enough not to call out a competitor, allow me. For those are expecting some more discussion from Amir here, they may be disappointed. He already has discussed these low impedance tests at length in other review threads. For example, the Audiophonics model using the same Hypex module failed the same test. Both @pma and I ran our own 2 ohm tests of our Hypex NC252MP amps and posted results in that review around page 8.

Amir is busy with his test backlog and should not need to repeat himself in every new review. He expects that ASR members are capable and will do some research. The ones that do not put some effort in are not likely to get him to respond by calling him out publicly on a review thread.

Despite the test causing both amps to go into protection, Amir recommended them. As you and others have pointed out, the test conditions are different. While some may feel a need to nitpick every spec, suggest they go do some comparison research before posting. Measurements matter but obsessing over one established measure repeatedly is not very productive for anyone.

 

[antcollinet]

If it's quite enough, surely, no doubt. But not if it's really loud and if the speakers are demanding. Amir's test tells the opposite. The job of tests is to reveal the limits. Because customer wants to see them. Btw: Amir's tests regarding power amps are much too good-natured. They should be much more demanding, more real life oriented.


True - but you can choose the easiest ones or the more demanding. Goal is to choose the most demanding, because all others will work afterwards. I'm not interested in easy use cases - I'm interested in the edge cases!

What? Full power sweeps over the frequency range not hard enough for you?

No amp will see high power at high frequency in real world music listening.

 

[restorer-john]

It could also have been a thermal shutdown.

More likely it was current sensing in the output filter via the dedicated winding for that purpose.

People need to understand that 2R is really close to a short circuit and the currents flowing are enormous. Once the phase is varied as the loadbox presents, that enormous current at 2R can lead the voltage causing the protection to trip as it 'sees' a large current but not a commensurate voltage. As the protection has to be really fast in order to save the output stage, it needs to act quickly to kill the SMPS. No time for averaging.

 

[amirm]

There continues to be some confusion about my reactive tests. The failure modes are not what people assume. The tests attempt to cycle between clipping (and sometimes way past that point) and not, attempting to find 1% THD point. Sometimes an amp never gets to that point. It either has 0.01% THD or shuts down. In these cases, the analyzer gives up with an error. I then try different input levels trying to get around this but at some point, just give up and state that the test failed. This does NOT mean that the amp cannot handle that load under any condition. It just means that the analyzer fails to find the 1% THD point.

I have sent in a feature request to Audio Precision to provide an option for the test to inch up to the THD level rather than jumping up and down to land in the middle. That would take longer to find the 1% THD point but has higher chances of getting an answer without pushing the amp into protection/shut down.

Also, there is a hardware bug in the Powercube load box where if the negative leg of amplifier output is at anything above 0, it will lock up and no longer function. I report these as failures but it is not a fault of the amp but the PowerCube.

 

[peng]

More likely it was current sensing in the output filter via the dedicated winding for that purpose.

People need to understand that 2R is really close to a short circuit and the currents flowing are enormous. Once the phase is varied as the loadbox presents, that enormous current at 2R can lead the voltage causing the protection to trip as it 'sees' a large current but not a commensurate voltage. As the protection has to be really fast in order to save the output stage, it needs to act quickly to kill the SMPS. No time for averaging.

Agreed, but note that in this case it tripped when V and I were in phase too. Hopefully Hypex will respond and tell us the 180 W 2 ohm's test conduction. I would still bet, as you alluded to, it's how they implemented the OC and/SC protection scheme, that is typically time based. SC could be instantaneous, OC will be time based so it most likely tripped on OC in this case. Again, I hope Dylan will soon let us know what Hypex may be willing to tell.

 

[peng]

There continues to be some confusion about my reactive tests. The failure modes are not what people assume. The tests attempt to cycle between clipping (and sometimes way past that point) and not, attempting to find 1% THD point. Sometimes an amp never gets to that point. It either has 0.01% THD or shuts down. In these cases, the analyzer gives up with an error. I then try different input levels trying to get around this but at some point, just give up and state that the test failed. This does NOT mean that the amp cannot handle that load under any condition. It just means that the analyzer fails to find the 1% THD point.

I have sent in a feature request to Audio Precision to provide an option for the test to inch up to the THD level rather than jumping up and down to land in the middle. That would take longer to find the 1% THD point but has higher chances of getting an answer without pushing the amp into protection/shut down.

Also, there is a hardware bug in the Powercube load box where if the negative leg of amplifier output is at anything above 0, it will lock up and no longer function. I report these as failures but it is not a fault of the amp but the PowerCube.

Thank you so much for the details, that explained a lot.

 

[restorer-john]

Also, there is a hardware bug in the Powercube load box where if the negative leg of amplifier output is at anything above 0, it will lock up and no longer function.

Are saying a single ended supply bridge tied load amplifier can't be powercube/loadbox tested?

 

[amirm]

Are saying a single ended supply bridge tied load amplifier can't be powercube/loadbox tested?

I have not done a full survey but yes, all the ones have failed so far have been such. The designer wants me to send him one of these amps but I have just been too busy to do that.

 

[Deleted member 48726]

There continues to be some confusion about my reactive tests. The failure modes are not what people assume. The tests attempt to cycle between clipping (and sometimes way past that point) and not, attempting to find 1% THD point. Sometimes an amp never gets to that point. It either has 0.01% THD or shuts down. In these cases, the analyzer gives up with an error. I then try different input levels trying to get around this but at some point, just give up and state that the test failed. This does NOT mean that the amp cannot handle that load under any condition. It just means that the analyzer fails to find the 1% THD point.

I have sent in a feature request to Audio Precision to provide an option for the test to inch up to the THD level rather than jumping up and down to land in the middle. That would take longer to find the 1% THD point but has higher chances of getting an answer without pushing the amp into protection/shut down.

Also, there is a hardware bug in the Powercube load box where if the negative leg of amplifier output is at anything above 0, it will lock up and no longer function. I report these as failures but it is not a fault of the amp but the PowerCube.

Aha!

 

[tmtomh]

So for the time being, the insistent demand that "you must test amps with complex loads" continues to generate more heat than light.

 

[Deleted member 48726]

So for the time being, the insistent demand that "you must test amps with complex loads" continues to generate more heat than light.

I'd say that it (THE CUBE) does what it's supposed to, roughly, which is exploring the limits of the tested product.

I think amir is right that it should not drive above the distortion limit to find 1 % but should slowly climb its way up from below.