Hypex NC252 failed (twice) -- suggestions for replacement?

[YouCanCallMeGeorge]

I've gone through two Hypex NC252 amplifiers in two years. The first unit failed after 10 months, and was replaced under warranty. The second failed after 12 months; it's now out of warranty.

The failure mode was the same for both units: The left channel dropped to five or ten percent power (relative to the right channel), and the sound content was half music and half fuzzy static. Normal operation returned after some hours with power off, and stayed normal for a few days. The second unit has gotten to the point that it will not hold full power on left channel for more than a half hour or so, and the right channel has been also been putting out fuzzy static (though right channel power is not diminished).

It may be that the case does not provide enough ventilation. It's a small Ghent case; the top sheet is perforated with small holes. With the first unit, the case felt warm to the touch (but not hot), even after sitting all night with no input and a low volume setting. With the second unit, I left the front plate off the case to improve ventilation. But the power devices are at the back of the case, and I don't know for sure what the temperature may have been at the heat sink. (The assembled amplifier was purchased from a reputable vendor. When the first NC252 failed I removed it and sent it to the vendor. I installed the second unit into the case myself, but did not disturb the wiring.)

I really like the sound from the Hypex. I have had an Onkyo tuner/amplifier for 25 years, which I bought for its low THD spec; it was a great improvement over the stereos I had previously owned. Hearing the Hypex for the first time I felt the same way: much better sound quality. Listening with eyes closed, I am often surprised just a little bit when I open my eyes and do not see the performers in front of me.

For reference, the other components in the system are a miniDSP SHD, LS50 Metas, and Rythmik servo woofers. The SHD is set to USB input 99% of the time. Since installation of sound absorbing panels, I have kept Dirac turned off.

I have two questions.

1. Has anyone else had problems with the Hypex 252? (I've seen the photos on this forum showing the gap between power device and heat sink. I'm wondering if anyone has seen actual failures, perhaps due to that cause. Admittedly, I did not go back to that long post today to read the latest entries, since I have a second question anyway.)

2. Are there any recommendations for other amplifiers that will provide the same quality of sound at 250 watts per channel rating? (I don't necessarily care if it's a D class amplifier; I just want good sound.)

 

[AdamG]

We happen to have a Fellow Member who builds class d amps and sells them here. Take a look:

Buckeye Amps

www.audiosciencereview.com

 

[pma]

I've gone through two Hypex NC252 amplifiers in two years. The first unit failed after 10 months, and was replaced under warranty. The second failed after 12 months; it's now out of warranty.

Similar issues here:

Class D amp long term reliability

Inexpensive today? A little over ten years ago Yamaha produced their NS-1000 speakers for $1000 a pair, and sold many. Today their replacement for the NS-1000 is their NS-5000 for $15,000 a pair, which granted their replacement is quite higher performance, but it sure doesn't seem to me like...

www.audiosciencereview.com

Reliability of Hypex modules - Early failure of NC252MP module

I use Nord-assembled 4-channel amps for my main system, which requires 8 channels for a pair of Linkwitz LX521.4. I bought the first of these two amps in Jan. 2020 for a pair of LXmini. They use the OEM NC252MP modules from Hypex. One 2-channel module within that amp has now failed. The other...

www.audiosciencereview.com

 

[Rick Sykora]

I would suggest a pair of Outlaw 2220s or for comparable money, upgrade to Hypex NC502MP if you are willing.

Finally, if you live close enough to me, would be willing to try to fix your amp. At least I can diagnose the issue and perhaps help determine whether it is worthwhile to fix or what might be better. I only charge $20 to diagnose. PM if you want to discuss.

 

[YouCanCallMeGeorge]

I would suggest a pair of Outlaw 2220s or for comparable money, upgrade to Hypex NC502MP if you are willing.

Finally, if you live close enough to me, would be willing to try to fix your amp. At least I can diagnose the issue and perhaps help determine whether it is worthwhile to fix or what might be better. I only charge $20 to diagnose. PM if you want to discuss.

It's worth 20 bucks to find out what can be learned from a post mortem. If it turns out the the amp can be fixed, I would put it in a larger, better ventilated case and see how it holds up. If it can't be fixed, I may learn something that helps me decide whether it's worth giving the Hypex NC252MP another shot in that larger case. (I really like the sound.)

 

[YouCanCallMeGeorge]

Similar issues here:

Class D amp long term reliability

Inexpensive today? A little over ten years ago Yamaha produced their NS-1000 speakers for $1000 a pair, and sold many. Today their replacement for the NS-1000 is their NS-5000 for $15,000 a pair, which granted their replacement is quite higher performance, but it sure doesn't seem to me like...

www.audiosciencereview.com

Reliability of Hypex modules - Early failure of NC252MP module

I use Nord-assembled 4-channel amps for my main system, which requires 8 channels for a pair of Linkwitz LX521.4. I bought the first of these two amps in Jan. 2020 for a pair of LXmini. They use the OEM NC252MP modules from Hypex. One 2-channel module within that amp has now failed. The other...

www.audiosciencereview.com

Thanks for the info. These reports make me leery of trying again with the NC252MP. On the other hand, there doesn't seem to be widespread failure of these units. Perhaps marginally poor ventilation in the small Ghent case pushes the temperature of the output devices up just enough to cause problems.

 

[Rick Sykora]

Lol, next time all us technical experts need to remember ask about loose output connections! We are often predisposed by our past influences that we neglect the basics.…

Anyway, glad you found the apparent cause. While quick connects are normally quite reliable, can get loosened as you push it on and perhaps was further stressed when you opened up the back panel. Let us know if you have any other issues.

Enjoy!

Rick

 

[YouCanCallMeGeorge]

Today I took the amplifier out of the case to have a look. As I slid the amp out, the plug that supplies power to the speakers was hanging loose. (There is no retaining clip or prong on the plug; friction between pins and sockets is all that holds the plug in place.)

The connector must have been in place before I slid the amplifier out, because the speakers had been producing sound (of a sort). The inference is that the plug was not properly seated, and that variations in power to left channel, and static on both channels, were due to poor contact between pins and sockets plus small variations in physical position due to heat or vibration.

I have the amplifier sitting on top of the case right now, with the plug fully seated. Both channels sound normal.

Very likely I caused the loose connector, as I had the back plate off for several weeks, in response to the loss of left channel around the first of the year.

The loose connector explains the most recent issues with the amplifier. However, both the original unit and the replacement unit exhibited loss of left channel, and static in left channel, after a year of good service. So there is something else wrong with the amplifier or the mounting arrangements.

The obvious suspect is overheating at the device level, given that the case was warm even with no audible output. I don't know that overheating is actually the cause, but it seems logical to put the amplifier into a bigger case with better ventilation.

The amplifier issues a temperature signal that originates with a Murata NTC (NCP18XH103J03RB). I will look into adding a connector plug and wires to monitor the temperature signal.

Thanks, @Rick Sykora , for your help.

 

[YouCanCallMeGeorge]

Update: The loose connector is for the signal inputs from the XLR connectors, not the outputs to the speakers.

This may explain both the intermittent loss of power to the left channel and the fuzzy static heard from the speakers, given that the cable plug has a propensity to slide away from the header on the board.

Another bit of evidence: Prior to sliding the amplifier out of the Ghent case, while investigating the static on the left channel, with amplifier and SHD preamp on, I turned the preamp off. I continued to hear the static. I then unplugged the left XLR connector, and the static stopped immediately.

It seems feasible that both the loss of power and the static are due to a poor connection at the input header (J4) on the amplifier board. This may not be an overheating issue at all.

I realized my mistake about which connector was loose this evening, when I had a chance for a longer look at the amplifier. I was mostly looking to see if it's feasible to use a latched plug on the cable, given that the plug slides out of the shrouded header so easily. There are holes in the shroud (on the board) that might be used as latching points. But I don't think it likely that a mating plug with a latch is available. The shrouded header is Amphenol T821116A1S100CEU. Substitute "01" or "02" in place of "00" and you get a latch on the shroud. The holes in the shroud are likely for the latch levers, not for a latch on the plug.

 

[Rick Sykora]

Yes, I have moved away from the Ghent design because of the misapplication of the idc connector with the Mogami cable. For those I own, I have placed some butyl rubber to keep them seated. For an amp that has to ship, would apply some hot glue or something stronger.

Hope this helps!

 

[YouCanCallMeGeorge]

Final update: This evening the lovely Head of the Hot Glue Application Department put a couple of beads of glue on the input signal connector (J4). This will keep the plug from slipping off the header pins. I enlarged 30 of the existing tiny holes in the top of the Ghent case to 1/4 inch diameter and assembled the amplifier. Then I listened to music of all sorts for three hours. The system sounds great, and at the end of the session the Ghent case was just barely warmer than ambient temperature.

 

[xyvyx]

Final update: This evening the lovely Head of the Hot Glue Application Department put a couple of beads of glue on the input signal connector (J4). This will keep the plug from slipping off the header pins. I enlarged 30 of the existing tiny holes in the top of the Ghent case to 1/4 inch diameter and assembled the amplifier. Then I listened to music of all sorts for three hours. The system sounds great, and at the end of the session the Ghent case was just barely warmer than ambient temperature.

I've had an NC252MP running in my office 24/7 for about 2 years now... it's been running fine so far, but it's pretty darn warm! (no music, just idle & 73F ambient)
I should take some measurements, then drill the holes out & see if/how much it helps.

 

[YouCanCallMeGeorge]

I've had an NC252MP running in my office 24/7 for about 2 years now... it's been running fine so far, but it's pretty darn warm! (no music, just idle & 73F ambient)
I should take some measurements, then drill the holes out & see if/how much it helps.

You might also think about fixing the J4 plug to the header. Rick Sykora mentions glue or butyl rubber (#10 above). There is an obvious audible effect of a poor connection at J4 (#9 above). I wonder whether a poor connection at J4 might also contribute to the mild heat buildup—though I have not even a conceptual basis on which to investigate such a cause. The connector labels are on the datasheet: https://www.hypex.nl/product/nc252mp-oem/76

 

[Willem]

I've had an NC252MP running in my office 24/7 for about 2 years now...

If it gets hot, it is time to cut your energy consumption by switching it off when not in use. This will save your amplifier, your wallet, and the planet.

 

[YouCanCallMeGeorge]

If it gets hot, it is time to cut your energy consumption by switching it off when not in use. This will save your amplifier, your wallet, and the planet.

As the author of the OP, it seems to me that the possibility of an amplifier overheating should not be taken as an opportunity to advance a personal off-topic agenda. Moreover, how another forum member chooses to spend his (or her) money is no concern of yours. As to saving the planet, I am reminded of the distinction that is made on this site between evidence based opinion, on the one hand, and mere assertion without evidential support on the other. My considered opinion, based on an ongoing review of the purported evidence, is that the claim of linkage between energy consumption and the imminent demise of the planet lands squarely in the audiophile section (as it were).

 

[Willem]

I disagree and I think the science is on my side as long as the energy is from fossil fuel. There is just no rational argument in favour of leaving gear on 24/7.

 

[restorer-john]

I disagree and I think the science is on my side as long as the energy is from fossil fuel. There is just no rational argument in favour of leaving gear on 24/7.

Absolutely correct.

Unless the amplifier is required for continuous 24/7 use in some situation like an airport background music system, there's zero justification for leaving it constantly turned on.

Apart from decreased life, there's the risk of overheating/failure/fire when nobody is around/asleep, risk of powerline surges etc. It's just a totally dumb idea and I cannot believe anyone with half a brain would even consider it.

 

[YouCanCallMeGeorge]

I disagree and I think the science is on my side as long as the energy is from fossil fuel. There is just no rational argument in favour of leaving gear on 24/7.

We can certainly disagree on a controversial subject. The controversy is the reason not to bring it up when not called for.

 

[YouCanCallMeGeorge]

Absolutely correct.

Unless the amplifier is required for continuous 24/7 use in some situation like an airport background music system, there's zero justification for leaving it constantly turned on.

Apart from decreased life, there's the risk of overheating/failure/fire when nobody is around/asleep, risk of powerline surges etc. It's just a totally dumb idea and I cannot believe anyone with half a brain would even consider it.

One of the beauties of a free country is that we do not have to justify ourselves to others in matters not governed by law.

 

[Willem]

You are free to believe whatever you want, but the causal link between fossil fuel consumption and global warming is not controversial but accepted science.