PMA-NC252MP power amplifier

[Sokel]

Agree that adding some extra protection against DC is a good idea.

However, Hypex seems to be stating that your amp is not in spec. So is not like they do nothing about DC protection. Are there ASR owners claiming speaker damage from a Hypex (or any other amp) for that matter?

A question based on Bruno's statement:
Are the current Hypex modules UL certified?If they are that answers it,isn't it?

EDIT:I found it on Ice Power PDF,is that what Bruno refers to?

I search Hypex's PDFs too,can't find it but OEMs must have more detailed ones so you can find them I think.

 

[mdsimon2]

Agree that adding some extra protection against DC is a good idea.

However, Hypex seems to be stating that your amp is not in spec. So is not like they do nothing about DC protection. Are there ASR owners claiming speaker damage from a Hypex (or any other amp) for that matter?

I've blown a woofer with a NC252MP as a result of a DC issue upstream. Fortunately it was a cheaper speaker I use for testing (Sony SS-MB350H) and was able to source a replacement for a few bucks on ebay.

While more robust DC protection would be nice, I personally blamed this event on the DIYINHK ES9016 DAC that was sending the DC and my own lack of proper power sequencing.

Michael

 

[Rick Sykora]

I've blown a woofer with a NC252MP as a result of a DC issue upstream. Fortunately it was a cheaper speaker I use for testing (Sony SS-MB350H) and was able to source a replacement for a few bucks on ebay.

While more robust DC protection would be nice, I personally blamed this event on the DIYINHK ES9016 DAC that was sending the DC and my own lack of proper power sequencing.

Michael

Ok, but did you stop using the Hypex amp or replace/fix the DAC?

p.s. My question is somewhat rhetorical as I know you are a smart guy. In any case, as I have said before, need more than one case to make a trend. Maybe the OP should get the UL certified ICEpower and see if it does any better.

 

[DonH56]

No. Any seriously designed amplifier, regardless it is DC coupled or not, has DC output protection circuit that disconnects output if the output DC voltage exceeds certain dangerous level, usually about 2V, that lasts more than fraction of a second. Even decades old commercial amplifiers had such protection circuits. My old and cheap Yamaha AX396 had such protection as well.

I'll bow to your superior experience. My memory is still colored by my old Phase Linear which would happily pass full rails to the speakers...

I am completely in the camp that DC protection should be provided. If they are selling modules to be plumbed by "anyone" IMO they should include that protection within the amplifier module and not depend upon integrators to do it.

 

[mdsimon2]

Ok, but did you stop using the Hypex amp or replace/fix the DAC?

I still use five NC252MPs.

The DIYINHK DAC was more of an experiment rather than something permanent as I have several all other multichannel DACs with better performance and no egregious on/off behavior.

Michael

 

[pma]

Anyway - seems we are on a good track with the manufacturer to fix the issue I have shown here! So, it definitely makes sense to do the extensive testing. A small reminder - we were on the good track with steel pads as well.

 

[pma]

I've blown a woofer with a NC252MP as a result of a DC issue upstream. Fortunately it was a cheaper speaker I use for testing (Sony SS-MB350H) and was able to source a replacement for a few bucks on ebay.

While more robust DC protection would be nice, I personally blamed this event on the DIYINHK ES9016 DAC that was sending the DC and my own lack of proper power sequencing.

Properly designed DC protection in the NC252MP would safe it, regardless power sequencing and DAC output DC. This is to be protected by the amplifier, and always was, for decades, in competent designs.

 

[MCH]

Would all this ever be an issue with a DC coupled balanced dac feeding a nc252mp or am I mixing apples and oranges?

 

[Rick Sykora]

A question based on Bruno's statement:
Are the current Hypex modules UL certified?If they are that answers it,isn't it?

EDIT:I found it on Ice Power PDF,is that what Bruno refers to?

View attachment 271373

I search Hypex's PDFs too,can't find it but OEMs must have more detailed ones so you can find them I think.

I see the same Hypex data sheets that you do…

They claim IEC 62386-1 safety certification but I do know that has some known conditions.

Cannot find any cert claim by Purifi.

Am still unsure of what the exact problem is being claimed about DC protection in this thread. @pma may be on to something but until it is confirmed by others, not sure it is one module, some of them or all of them.

 

[pma]

Would all this ever be an issue with a DC coupled balanced dac feeding a nc252mp or am I mixing apples and oranges?

Under normal working conditions there will be no problem. If the DC coupled balanced DAC would put DC at the output as a result of hardware or software error, there might be the issue exactly as I have shown.

 

[Rick Sykora]

A quick follow-up on the safety certs as I neglected to mention that Bruno’s point is valid regarding end product responsibility...

You could take a box and put some binding posts on it. In one case, put a Hypex NC252MP and in another put an SMPS1200A400. Both modules have IEC 62386-1 certs, but hook your speaker to the one with just the SMPS and your speaker is cooked.

 

[restorer-john]

My memory is still colored by my old Phase Linear which would happily pass full rails to the speakers...

But that was when it exploded, Don! Flame Linears/Blaze Linears. LOL

Seriously, at least they (PL) were smart enough to give you a choice whether you wanted to destroy your speakers or not, unlike Hypex.

They gave you a switch: Do I feel lucky? Well, do ya, punk?

 

[DonH56]

But that was when it exploded, Don! Flame Linears/Blaze Linears. LOL

Seriously, at least they PL were smart enough to give you a choice whether you wanted to destroy your speakers or not, unlike Hypex.

They gave you a switch: Do I feel lucky? Well, do ya, punk?

View attachment 271477

Yeah, the switch was helpful, but not when the output transistors shorted and applied one of the rails across the speaker(s). It was after the third time that happened, burning the woofer wire in my Maggies, that I finally fixed it and sold it cheap with the condition that I never saw it again...

I was in college at the time and they actually had some Blaze Linears they were using in one of the labs as a DC supply source to model a power supply with added noise. The waveform looked similar to @pma's plot, a sine wave offset from ground by a significant amount. The DC Input worked well for that. And I am pretty sure they had a drawer full of output transistors on hand... They also mounted fans on them as they tended to run hot.

 

[restorer-john]

And I am pretty sure they had a drawer full of output transistors on hand...

Love it.

 

[pma]

Unfortunately, my e-mail communication with Hypex tech support turned out in disappointment. They confirmed what I measured, once again:

when in case that only one channel is exposed to DC input error voltage, the DC protection was activated at 26V. They use only one DC sensing circuit for both channels, and they monitor outputs via 2 resistors. In case that one channel sees input DC and the other one does not, the resistors create a divider and the DC error threshold is twice higher.
Hypex declare the output DC threshold of 12V, but it is in case that both channels see the same input dc. If only one sees dc, and the other one sees 0V, the threshold would be 24V.

The frustrating point is that Hypex do not see 12V (or 24V) permanent output dc as a problem. Yes, that much, because the DC protection works only above this level.

Instead, they recommend:

the DC error is only added in case of a fault to prevent external damage.
It is advised to prevent any DC on the input since they are DC coupled, otherwise you can make the input AC coupled to filter out any DC.

For this reason, and behaviour shown, I do not recommend Hypex NCxyzMP modules in case that someone asks my advice.

 

[Sokel]

Unfortunately, my e-mail communication with Hypex tech support turned out in disappointment. They confirmed what I measured, once again:

View attachment 271903

when in case that only one channel is exposed to DC input error voltage, the DC protection was activated at 26V. They use only one DC sensing circuit for both channels, and they monitor outputs via 2 resistors. In case that one channel sees input DC and the other one does not, the resistors create a divider and the DC error threshold is twice higher.
Hypex declare the output DC threshold of 12V, but it is in case that both channels see the same input dc. If only one sees dc, and the other one sees 0V, the threshold would be 24V.

The frustrating point is that Hypex do not see 12V (or 24V) permanent output dc as a problem. Yes, that much, because the DC protection works only above this level.

Instead, they recommend:


For this reason, and behaviour shown, I do not recommend Hypex NCxyzMP modules in case that someone asks my advice.

I would really,REALLY like someone to do the same test to Ice Powers and Purifis,after that I'm suspicious about all of them.
If someone has any of such modules and the skill please do it,it would be of great service to the community.

 

[Rob Fens]

Twenty-five years ago i used an Bose 1800 power amp for the bass, dc hammered both woofers with a loud bang, the voicecoil was not anymore in, but on the pole plate...
After reading the posts of PMA i really wonder if an audio brand which is using OEM parts only has to put them into a box and make it look smart.
I guess an OEM supplier does only supply the parts, the audio brand has to compose the parts into something he can be proud of, what else will give added value?
This composing consists of adding parts and arranging stuff so it will produce the best he can. For this reason brands play with different PSU, input boards etc.
If the audio brand is unhappy with some characteristics of the OEM part, he can also make improvements or add circuitry, which can turn it into a distinguished product.

 

[Paul Ebert]

Would this problem be resolved by the inclusion (DIY addition) of something like this?

Single Supply BTL Amplifier Speaker Protection

 

[pma]

Would this problem be resolved by the inclusion (DIY addition) of something like this?

Single Supply BTL Amplifier Speaker Protection

Unfortunately not, because the project that you have linked is dedicated to amplifiers with single-supply (single polarity) power supply and bridged output. The correct ESP project is this one:

Loudspeaker Protection and Muting

ESP Project Pages - Loudspeaker Protection and Muting. Protect you loudspeakers from amp DC faults

sound-au.com

 

[somebodyelse]

Could you add your own DC detection and pull nFatal low via J7.5 to trigger the built in DC protection shutdown?