[farquad]

Basically you have to make sure all the circuits are sufficiently isolated from the case (and that means not connecting the nc400 base plate to the case).

My personal answer would be "if you have to ask, don't even think about it"

Did he at least work for the Department of Transportation?

Isnt it odd that the "preferred connection" in the datasheet of the ncore400 is without mains safety earth and not saying anything about not mounting the baseplate directly to the case?
I get that "preffered connection" refers to the sonic qualities, but it should still have been mentioned it limits the ability to mount the base plate directly to the case.

[Julf]

Isnt it odd that the "preferred connection" in the datasheet of the ncore400 is without mains safety earth and not saying anything about not mounting the baseplate directly to the case?
I get that "preffered connection" refers to the sonic qualities, but it should still have been mentioned it limits the ability to mount the base plate directly to the case.

Well, it does state "acceptable if class II construction is used throughout".

[farquad]

Yeah but it says nothing about wether the ncore400 module is a safety class II device or not.
In the SMPS1200 datasheet it is stated it is a safety II device. The SMPS1200 is mounted on an aluminium frame and mounting the SMPS1200 directly on a metal chassis should still comply with safety class II?

The PCB and the metal base on the ncore400 seems to be separated by more than 6mm so why doesnt mounting the metal base to a metal chassis comply with safety class II? Isnt there enough insulation between the parts on the PCB and the metal base?

If this is the case it seams the "preferred connection" of this piece of DIY-targeted electronics isnt preferred for DIYers.

[HighRez]

My method of building a Class II chassis was to use a 3mm thick sheet of Teflon between the SMPS and the Aluminum chassis base while still maintaining the connection of the metal standoff foot via stacked washers that are the same thickness as the Teflon sheet. The washers are then sandwiched in between both connection points. The Teflon sheet is said to have a high dielectric property, is non-flammable and maintains a melting point of near 600deg F.

I would imagine that as long as the umbilical itself that connects the SMPS600 to the NC400 was also "double shielded" it would suffice in maintaining Class II chassis status. I wasn't under the impression that the NC400 aluminum base was NOT "live" cause if it were I would have expected to see the same cautionary text in the whitepaper with a "Red" outline around its circumference like on the SMPS600 highlighting this possibility. Obviously the problem with lifting the NC400 from the chassis is you would lose a great deal of cooling unless you account for such issues with sufficient venting in other places nearby.

In my case, despite building the chassis in such a way that would allow me to "unearth" the IEC safely I'm not sure yet if I will go that route or not. Most likely I will earth it first and see how it sounds. If I hear any hum/hiss I will then move onto the unearthed approach. I think with using the Teflon sheet, even if I use an earthed connection, it will help reduce any chances of stray voltage from the SMPS600 to the chassis. At least that's the theory...

I read in another post one member who was able to measure some level of stray voltage within the chassis coming from the SMPS600 thus they decided to earth it as a CYA in fear of electrocution.   

[Julf]

Yeah but it says nothing about wether the ncore400 module is a safety class II device or not.
In the SMPS1200 datasheet it is stated it is a safety II device.

And the same goes for the SMPS600.

I agree Hypex should have been clearer and more explicit about how well the nc400 base plate is isolated. Without knowing what isolation tests Hypex have done, there is no way I would state on a public forum that attaching the nc400 base plate to a metal enclosure will satisfy class II requirements - and anyway, class II requires taking care of a lot of other things too, so I fully agree with the recommendation from Hypex: "No safety earth connection was depicted. This is entirely acceptable if class II construction is used throughout. Otherwise, connect the safety earth."

If this is the case it seams the "preferred connection" of this piece of DIY-targeted electronics isnt preferred for DIYers.

Indeed it isn't. I think Bruno has indicated that the preference for the "preferred connection" isn't very strong. So, again - unless you are familiar with class II requirements and design, and know what you are doing, connect safety earth.

[HighRez]

Jut adding some additional info here about the baseplate on the NC400. I used my multi-meter and connected on of the leads to the earth pin on the IEC Input and touched the other lead to the baseplate on the NC400 and it did not result in a "Short". I am assuming this is because of the coating on the NC400 baseplate. I am also assuming this is expected but please chime in if you feel that doing this should have resulted in a "Short" on the multi-meter. All other areas of the chassis near/around the NC400 baseplate did result in a "Short".

The plate does indeed look to be made of Aluminum but the coating seems to be the insulator preventing the short. I wonder what happens if this plate becomes live by accident as the result of the coating be scratched? 

[Atlplasma]

Jut adding some additional info here about the baseplate on the NC400. I used my multi-meter and connected on of the leads to the earth pin on the IEC Input and touched the other lead to the baseplate on the NC400 and it did not result in a "Short". I am assuming this is because of the coating on the NC400 baseplate. I am also assuming this is expected but please chime in if you feel that doing this should have resulted in a "Short" on the multi-meter. All other areas of the chassis near/around the NC400 baseplate did result in a "Short".

The plate does indeed look to be made of Aluminum but the coating seems to be the insulator preventing the short. I wonder what happens if this plate becomes live by accident as the result of the coating be scratched? 

Did you also put the probe into the mounting holes for the screws? Just curious.

[farquad]

Thanks for the info.

[Active-6way]

Hello guys,

I need some advice; i have build an ncore amp in an chassis that is for an HTPC : the streacom fc5-ws http://www.streacom.com/products/fc5-ws-fanless-chassis/ Now in the front there is an blue light that can be attached to an motherboard.

Can anybody telle me how to connect this to the amps or the  powersupply so that if the amp is powered on that the led will light up ?


Thx

[HighRez]

Hello,

IMO it my be easier to hog out the hole where the Blue LED currently resides and replace it with a Illuminated pushbutton power switch like the one below. That way you can just wire it up inline with your IEC power Input.

http://www.nkkswitches.com/series.aspx?stid=3&id=5073

The SMPS has AUX output jumpers (J1) on it but, again IMO, I would avoid using them for this purpose

[srb]

IMO it my be easier to hog out the hole where the Blue LED currently resides and replace it with a Illuminated pushbutton power switch like the one below. That way you can just wire it up inline with your IEC power Input.

http://www.nkkswitches.com/series.aspx?stid=3&id=5073

I have a few questions on the power switch you linked to:

1.  Although few would drive the amplifier to it's maximum output, does an AC switch rated at 3A have the necessary safety margin for a 600W power supply running off of 125VAC line voltage?

2.  Because the built-in light is an externally powered LED requiring ~ 2VDC (or higher if a ballast resistor used), where is that DC voltage connection sourced from the SMPS600?

Thanks,

Steve

[HighRez]

Hello,

From what I see on the spec sheet it looks like that switch can be used in AC or DC configurations so there shouldn't be a need to have a DC feed from the SMPS.

I can't speak to the safety margin but it does say it can be used in 125VAC or 250VAC applications @ 3A. Whether that specific switch is adequate would depend on how many Watts one expects to draw for the intended application.

I linked to that one more so as an example of what I was speaking about in my previous post but there are other higher rated units on the market that can handle more Amperage.

Here is another one below of the toggle type and is illuminated with a 6A rating and may be a better match. Based on my calculations 125v @ 600w = 4.8A leaving 1.2A of headroom

http://www.nkkswitches.com/series.aspx?stid=13&id=5061

At the end of the day if someone wants to have some form of indication that the amp is powered up the safest approach would be to leave a hole in the chassis so you can see the built-in LED on the board of the NC400 module or as an alternative just buy a IEC power Input with an illuminated On/Off switch and skip the remote LED altogether.

[srb]

From what I see on the spec sheet it looks like that switch can be used in AC or DC configurations so there shouldn't be a need to have a DC feed from the SMPS.

Yes, the switch contacts can be used to switch an AC or DC circuit, but because the lamp is an LED (and this particular switch doesn't have a built-in chip rectifier/power supply like LED home light bulbs), the switch does have separate lamp terminals that require a DC voltage to operate.

I can't speak to the safety margin but it does say it can be used in 125VAC or 250VAC applications @ 3A. Whether that specific switch is adequate would depend on how many Watts one expects to draw for the intended application.

Exactly, and because the amp might later be use by another person with less sensitive speakers and higher power demands, as well as the fact that although the SMPS is very efficient it's efficiency is somewhat less than 100%, I would be inclined to use the 6A rated switched on a 125VAC line input, although on a 250VAC line input the switch would need to only carry half the current and the 3A would be fine.

Steve

[jult52]

I am a fan of Class D amplification but not a fan of switch mode power supplies.  Has anyone been experimenting with driving the Hypex nCore module with an appropriately matched regulated linear power supply?  I know they would use a lot more energy, but wouldn't this yield potentially large benefits In Sound quality?

[Rclark]

Extremely doubtful. Look at the performance charts for the amp and ask how a linear supply would improve on that.

You could change the sound with a different supply but ultimately probably just degrade it. Imo would have to be an absolute top flight linear supply designed specifically for this amp.

The resistance against a switcher is the same as the resistance against class d. It doesn't make sense to you that there is a switcher used with this amp. But when you hear it, any concerns will melt away.

I have another amp and for it I have a switcher (which is terrible), a big linear supply, and also batteries for it. This ncore with its switching supply destroys that amp with any PS configuration.

The switcher on the ncore is as advanced as the amp itself, so your fears are unfounded and out of date. It's extremely good.

[jult52]

I'm not sure why the aggression in your reply, rclark.  All of the specs I have seen indicate that well-made linear power supplies outperform switching supplies.  There's nothing out-of-date about that position.  In fact, there have been some recent linear power product introductions that seem to be a step forward vs older models.

So can anybody reply to my question or has the idea of driving an nCore with a linear supply not been tried?

[cab]

It has been tried. Search the thread at diyaudio. Reports are the differences are not significant and in light of the added complexity, cost, weight, etc., not worth the trouble.

[Rclark]

I'm not sure why the aggression in your reply, rclark.  All of the specs I have seen indicate that well-made linear power supplies outperform switching supplies.  There's nothing out-of-date about that position.  In fact, there have been some recent linear power product introductions that seem to be a step forward vs older models.

So can anybody reply to my question or has the idea of driving an nCore with a linear supply not been tried?

Apologies. Just saying that in this case I think it would have to be a purpose built linear supply, if a linear supply were to provide any improvement, if possible.

I am of the mind that improvements would come with a next gen switching supply by Hypex, something that improves on the smps600. Not an off the shelf linear supply.

[srb]

There are quite a few manufacturers using their own linear power supplies with the Hypex UCD modules.  I agree that there would (should) be some knowledgeable design that would go into building a linear supply for the Ncores, rather than the average DIY guy just slapping together a transformer, rectifiers and filter caps.

Part of the reason we haven't seen it for the Ncore 1200 might be that it would take a very heavy and expensive power supply be able to output a maximum of 1200W at 2 Ohms.  As the current manufactured Ncore 1200 amplifiers are selling for ~ $10,000 to $15,000 / pair, I would expect that the same amplifiers with beefy linear power supplies would be selling for an additional ~ $3,000 to ~ $5,000 per pair.

As far as Hypex and Bruno Putzey is concerned, I'm sure lighter, smaller, cheaper and more efficient is the view for the future world, not heavier, larger, more expensive and less efficient.

Steve

[lowtech]

"Knowledgeable design"?  There are only so many ways to build an unregulated linear power supply and I assure you it's not rocket science.