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Old 23rd June 2012, 12:15 PM   #4551
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Quote:
Originally Posted by Abraxas336 View Post
However - as far as I know it is not sufficient to have 10 mm clearing between metal case and hazardous voltage to meet class II requirements. That's class I. Might be wrong, though. Bruno will certainly comment.

Regards
Sven
Checking class I and II requirements I don't find anything on distance clearing.
Class I: safety by connection to earth (ground);
Class II: no connection to earth (ground) but double insulation of voltage carrying parts.
The datasheet of the SMPS600 is very clear: use the 10 mm spacers to get at least 6 mm clearance; when using shorter spacers (having the power supply fitted in a 1U enclosure) apply an additional layer of insulation between SMPS600 and chassis .
What's the problem??
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Old 23rd June 2012, 12:33 PM   #4552
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Pieter,

There is no problem. Again, as far as I know:

In order to build something with a metal case that is not immediatly deadly you need an insulation. That - for instance - can be >=6mm clearing. If you're getting below 6mm you need additional insulation. However, it's still class I and you need to connect saftey earth.

If you want to build something with a metal case that meets class II (thus, doesn't need saftey earth) you need a double insulation. E.g. a seamless plastic housing around your metal housing. This is normally used for handheld tools like hair dryers etc..

A good example for why this is so is Simtu. What he is measuring could be deadly. His picture looks like he has no saftey earth connected. It is not unusual that there is some potential between ground/earth, if there really was a significant current flowing the earth leakage circuit breaker would tell him.

Regards
Sven
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Old 23rd June 2012, 01:13 PM   #4553
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Quote:
Originally Posted by Abraxas336 View Post
Pieter,

There is no problem. Again, as far as I know:

In order to build something with a metal case that is not immediatly deadly you need an insulation. That - for instance - can be >=6mm clearing. If you're getting below 6mm you need additional insulation. However, it's still class I and you need to connect saftey earth.

If you want to build something with a metal case that meets class II (thus, doesn't need saftey earth) you need a double insulation. E.g. a seamless plastic housing around your metal housing. This is normally used for handheld tools like hair dryers etc..

A good example for why this is so is Simtu. What he is measuring could be deadly. His picture looks like he has no saftey earth connected. It is not unusual that there is some potential between ground/earth, if there really was a significant current flowing the earth leakage circuit breaker would tell him.

Regards
Sven
Sven,

I have quite some electronics in the house which are housed in metal cases, and which meet class II, with 2-pole power cords (unearthed). Obviously the inside electronics should meet class II requirements.
IMO the NC400/SMPS600 combo can perfectly be built into a metal enclosure following class II without earthed power cords, so connecting the amplifier to an unearthed mains outlet (which will actually very often be the case in practice also with the class I built...).
When someone does not trust his abilities in this regard it is quite logical to build class I with appropriate earthing, but it is not a necessity.
In Hypex datasheets I see no indication to do so.
Also take a look at Hypex' application note on earthing/insulation.

Last edited by pieter t; 23rd June 2012 at 01:38 PM.
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Old 23rd June 2012, 02:49 PM   #4554
DavidT is offline DavidT  United States
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Here are some measurements taken from my quad amp chassis, employing dual UCD 400 for bass, and dual NC 400 for the higher ranges. Cooling holes on lower chassis, open top, user heat sinks for amps. One SMPS per amp pair (total of two SMPS)

Instrument: FLUKE 179 True RMS VM, using Type K thermocouple (TC)

Calibration: Boiling H2O @ 102 C ( 2 C correction required ), room air @ 21.5 C

Method: Amp at idle for 1 hr. Finger press TC bead against surface using a 0.5 mm thick coated fiberglass protective cloth until temp reading stabilizes. Record non-corrected data.

UCD 400

Output inductor: 46.0 C

Main electro-cap: 42.1 C

Blue T-Bar: 42.1 C

User heatsink: 37.7 C

non HS TO-220 devices: 71 C ( too hot to touch)


NC 400

Output inductor: 46.5 C

Electro caps: 38.2 C to 52.7 C ( too hot to touch)

User heat sink: 34.3 C


SMPS 600

Main xfmer: 47.7 C

Small HS: 36.0 C

Large HS original: 46.5 C

Large HS w/ user CPU style HS added: 38.2 C


Note: temps will be higher with the vented top installed...

************************************************** ********

BTW, all 4 amps output ~ 190 WRMS into 8 ohms, both channels driven, just before clipping, with 120 VAC line voltage

That is: 190W * 4 = 0.760 KW! Yowzer!

Regards, DavidT
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Old 23rd June 2012, 08:31 PM   #4555
Simtu is offline Simtu  England
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Quote:
Originally Posted by pieter t View Post
Simtu,

The SMPS600 is mounted on stand-offs, and it's hot parts do not make contact with the chassis, so the extra heatsinks are of very little value to remove the heat of the power supply.
The original case should be sufficient to dissipate the heat of the Ncore module.
As your amplifier is in a closed cabinet you should improve air flow.
As Ian suggested make some openings in the ground plate to improve convection.
A slow (and inaudible as it's inside the cabinet)) fan might be a better approach to get rid off excessive heat.

Good luck with solving the electrical problem.
I added the additional heatsinks in order to increase thermal mass and total surface area, in order to dissipate heat at a greater rate. Once this heat has radiated into the air within the enclosure, the additional heatsinks that I have added to the enclosure will again assist in dissipating the heat to the outside. This system of heat transfer may be relatively inefficient but it must surely help to improve the cooling. I will also be asking Modu2000 for a quote to produce some custom enclosure panels with additional ventilation slots though. The various merits of adding extra heatsinks was discussed earlier in this thread and it seemed a good idea. Beginning to wish I hadn't bothered. Ah the benefits of hindsight.......

This afternoon, I swapped the two SMPS's around without changing anything else, and hey presto the other amplifier works again. The problem must be somewhere on the smps board although I can see nothing visual to suggest a short - the problem must presumably come down to a component failure. The question is why would this occur at the same time that I glued a couple of heatsinks in place? Can anybody hazard a guess where the fault may lie? To reiterate, I have been over the entire circuit board and there is no foreign matter anywhere and nor is there any obvious sign of discolouration/burning etc. Would the failure of any particular component result in a short to ground (presumably via the conducting corner stand off)?

I would love to avoid the expense and hassle of returning the faulty SMPS to Hypex so would welcome any and all further advice. Thanks in advance
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Old 23rd June 2012, 09:35 PM   #4556
Ianmac is offline Ianmac  Scotland
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If the amp is now working after you have swapped SMPS boards it could be that your problem is associated with the interconnect cable.

Check the suspect amp interconnect at the SMPS end and ensure all the pins are fully home into the plastic connector. The pins are crimped onto the cable and unlikely to be problematic. After wiring, the pins themselves are inserted into the plastic connector and held in position by two small metal wings in the pin mating with shelves in the connector. If the pins are accidentally twisted through 90 deg this holding arrangement can fail leaving the pin loose in the connector and not mating correctly with the associated socket on the SMPS plug.
I found this when making my own interconnect cable

Try moving the cable and see if you can replicate the fault
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Old 24th June 2012, 02:45 AM   #4557
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Hello Group! I am new here, but have been watching this thread for quite some time. I have finally ordered 2 NC400 and 2 SMPS and await the email that they have shipped! As I wait, I have been shopping for enclosures and the other components needed to put these amps together. My questions are as follows: Are there any disadvantages to putting two of these amps in one enclosure like siliconrays RE4307. Would it be better to get 2 RE2207's? I am new to the DIY audio world so I also need a little direction in picking out the best affordable XLR inputs, binding posts, and IEC sockets. I apologize in advance if this topic has already been touched on, but I have spent hours reading and haven't found a good answer!

Thanks in advance,
Brandon
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Old 24th June 2012, 06:52 AM   #4558
Julf is offline Julf  Europe
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Quote:
Originally Posted by firemanbrandon View Post
I have finally ordered 2 NC400 and 2 SMPS and await the email that they have shipped!
Welcome to the club!

Quote:
My questions are as follows: Are there any disadvantages to putting two of these amps in one enclosure like siliconrays RE4307. Would it be better to get 2 RE2207's?
I would say it comes down to cost and form factor. Two amps in one box should not be an issue - some of us are putting 4 (or even more) nCores in the same box, and then getting rid of the heat is starting to become an issue.

Quote:
I also need a little direction in picking out the best affordable XLR inputs, binding posts, and IEC sockets.
On the XLR's and IEC sockets, go for whatever normal stuff you have easily available locally. No real benefit from fancy stuff. On binding posts, just make sure they have enough current carrying capability and low resistance, as you don't want to hurt the damping factor (the output impedance of the nCore is *very* low). I am sure there will be people recommending fancy, expensive connectors, but the nCore really doesn't need any audiophile voodoo.
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Old 24th June 2012, 08:59 AM   #4559
matjans is offline matjans  Netherlands
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great to see this thread is still going on, well over the 4000 mark.

Anyway, as Julf said, no voodoo is necessary. Good quality mechanics are, however, in order to squeeze the most out of the ncore's so just get good quality connectors; neutrik xlr's (the de facto industrial standard, so to say), good quality speaker binding posts (if you ask Bruno, he'd say use neutrik speakon's), don't forget something like good spades for speaker cable connect.

mono vs stereo vs multichannel amp is more a matter of taste and budget (and waf) than true audio related i would think.
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Old 24th June 2012, 02:56 PM   #4560
Regnad is offline Regnad  United States
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So sorry if I have missed this, but...

Has anyone built a bridged NC400 unit yet that can report back on the method and results?

Thanks!
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