[Rclark]

Ok, for some reason this: "connecting the chassis to the safety earth terminal of the power line. I did not say ground, though ultimately this is connected to the physical ground/earth near the panel where the power enters your premises" sounded pretty involved.

 If it's just making a connection to the chassis, that can't be too difficult then. I've built crossovers from scratch, hopefully that's enough experience to do this. I'd like to buy an inexpensive, plain box I can drill into and mangle, so I can learn it, and then get some nicer monoblock cases later. Unless monoblocking in seperate enclosures makes no difference.

[doug s.]

I wasn't trying to be an ass. Playing with mains power is potentially fatal. A quick Google or other search will turn it up quick enough. Basically a safety earth is connecting the chassis to the safety earth terminal of the power line. I did not say ground, though ultimately this is connected to the physical ground/earth near the panel where the power enters your premises.

I did add these to my amps. As they say, a photo is worth a thousand words.

mike, are you using the xlr inputs, or the rca's?  according to hypex, you want to connect a cap & resistor in parallel between the rca input ground and the chassis, if you are grounding the mains.  (see fig. 5 on pg. 13.)
http://www.hypex.nl/docs/NC400_datasheet.pdf
and, if you are using true xlr balanced cables, there is no indication of what you should do (if anything?) if you still want to ground the mains. (per fig. 2, pg. 12.)  it does say you can ground the mains if you are using an xlr-to-rca cable, wired per fig. 3, pg. 12, if class ll construction has not been followed...

thanks,

doug s.

[James Romeyn]

I presume Rclark understands the purpose of the chassis earth: any positive mains voltage accidentally shorted to the chassis (earth) opens the amp's fuse and likely the mains circuit breaker.  Sans chassis earth: any positive mains voltage shorted to the chassis results in a hot chassis shorting to earth through whoever/whatever contacts the chassis.  Ouch! 

Unbalanced input wiring:

Bruno prefers and recommends XLR input over RCA, and diagrams the XLR input even with unbalanced source.  Connected as directed he says unbalanced source performance approaches balanced source. 

At this amp's advertised performance level I can hardly believe any owner with unbalanced source would employ RCA input considering the Ncore inventor's advice.  How difficult is it to make 2-conductor shielded interconnect with RCA plug @ the source and XLR plug @ the load?

Polarity inverting switch:

I have a polarity switch upstream so no interest in this.  It might benefit another user.

Hypex would have to authorize the following switch, which might cause failure or audible noise in use, possibly fixed with a capacitor across the switch.  A DPDT switch on the two balanced input wires, for normal polarity or inverted polarity.

My Trinaural processor has balanced outputs, currently connected between the source and analog multi-channel preamp, allowing remote level adjustment for the bass and center channel (bass fairly often, center almost never).

Inserting the Trinaural between the preamp and Ncore amps would change the Ncore amp inputs from unbalanced to balanced, potentially improving performance, but at the expense of the remote bass/center channel level adjustments.       

[jtwrace]

Ok, for some reason this: "connecting the chassis to the safety earth terminal of the power line. I did not say ground, though ultimately this is connected to the physical ground/earth near the panel where the power enters your premises" sounded pretty involved.

 If it's just making a connection to the chassis, that can't be too difficult then. I've built crossovers from scratch, hopefully that's enough experience to do this. I'd like to buy an inexpensive, plain box I can drill into and mangle, so I can learn it, and then get some nicer monoblock cases later. Unless monoblocking in seperate enclosures makes no difference.

This is what Mike added.... see the RED circle with the RED arrow.  The green wire, that's the ground wire. 

What he didn't show was that after you do this you need to check and make certain that you have continuity between the ground lug on the IEC and the chassis.  Adding the wire is great but it doesn't work if there's paint or anodize.  Be sure to clean it off and use a DMM!!!  His chassis is obviously bare aluminum.

[Big Red Machine]

So I will be watching and learning to see how/what any RCA connection set-ups require additional noise suppression, if any.  I have single ended pre so only SE amps will work.

[jtwrace]

So I will be watching and learning to see how/what any RCA connection set-ups require additional noise suppression, if any.  I have single ended pre so only SE amps will work.

Not true. I have SE pre and it works fine.  Read the NC400 data sheet.

http://www.hypex.nl/docs/NC400_datasheet.pdf

[mgalusha]

mike, are you using the xlr inputs, or the rca's?  according to hypex, you want to connect a cap & resistor in parallel between the rca input ground and the chassis, if you are grounding the mains.  (see fig. 5 on pg. 13.)
http://www.hypex.nl/docs/NC400_datasheet.pdf
and, if you are using true xlr balanced cables, there is no indication of what you should do (if anything?) if you still want to ground the mains. (per fig. 2, pg. 12.)  it does say you can ground the mains if you are using an xlr-to-rca cable, wired per fig. 3, pg. 12, if class ll construction has not been followed...

Doug, the RCA and speak on connectors are not wired, strictly XLR balanced input. Source has a transformer on the output and proper pin 1 connection, so no troubles there.

[mgalusha]

What he didn't show was that after you do this you need to check and make certain that you have continuity between the ground lug on the IEC and the chassis.  Adding the wire is great but it doesn't work if there's paint or anodize.  Be sure to clean it off and use a DMM!!!  His chassis is obviously bare aluminum.

Good point. The chassis is actually clear anodized. I use a counter bore style drill bit, by hand, to remove the anodize around the holes. This was done for the XLR ground, the noise post of the SMPS and of course the IEC where the safety is connected.

mike

[doug s.]

Doug, the RCA and speak on connectors are not wired, strictly XLR balanced input. Source has a transformer on the output and proper pin 1 connection, so no troubles there.

hi mike,

so, your connection is yust like fig. 2, pg. 12?  and you simply added the mains earth connection w/o any addition of cap or resistor at the xlr's pin-1 ground?

thanks,

doug s.

[mgalusha]

Doug, yes that is what I did. I like the idea of preferred.

[doug s.]

Doug, yes that is what I did. I like the idea of preferred.

"preferred" sounds good to me, too!     i was yust wondering how you did it, cuz the hypex diagram indicated no earth mains ground is necessary, and i was wondering if any cap/resistor set-up needed to be added, when you did the earth mains ground...

one day, i may have to have a go w/these...   

thanks,

doug s.

[mgalusha]

Doug,

The PS is rated as class 2 provide it's mounted via insulated posts and has the required clearances but I didn't care for the leakage voltage between neutral and the chassis, so I opted for the safety earth connection. In my system this didn't seem to cause any noise problems but I have built my preamp with balanced outputs and followed the recommended standards (AES48) for dealing with pin 1.  Rane has a nice page summarizing this. IMO the Rane document should be required reading for all persons interested in audio.

[doug s.]

mike, your fleshing out the details is really appreciated by us nowices, who can basically only swap out parts!     i noticed the leakage you were having; grounding makes sense, if there's no further noise issues.

doug s.

[poseidonsvoice]

Doug,

... Rane has a nice page summarizing this. IMO the Rane document should be required reading for all persons interested in audio.

I agree.

After that, interested readers should also take a close look at Dave Davenports Audio Component & Grounding article. Here is the pdf version, which might be an easier read for some of you.

Best,
Anand.

[HT cOz]

OT, If you are looking for cases, I have 7 in stock.

Thanks,
Robert

[roscoeiii]

These cases for monoblocks or could I put a stereo ncore in one?

[mgalusha]

If they are the same as the previous batch in size, there is only room for a single channel.

[Occam]

We appear to be co-mingling technical issues here, which is quite understandable.
A balanced interface does indeed lower the incursion of noise via cabling. This does not requires a differential signal, but simply a balanced impedance of the 2 signal wires, + & -. That is easily accomplished with single ended signal outputs, like so -


from -
http://www.jensen-transformers.com/an/an003.pdf
at
http://www.jensen-transformers.com/apps_wp.html

And with the proper balanced interface load end circuitry, one has the noise rejection benefits of a balanced interface. While shielding is effective, to varying degrees against RFI incursion, unless your cable shielding is 1/4" permeable steel, nothing other than a balanced interface is effective against strong EM fields.

While the single ended source shielded twisted pair terminated with a balanced XLR, as recommended by Hypex, will provide some of the benefits of the balanced interface, specifically ground loop minimization, common mode noise supression is substantially compromised without a balanced impedance interface. For those with diy single ended preamps, adding a balanced impedance output is quite straightforward. YMMV

FWIW,
Paul

[siliconray]

Nice work. The enclosure has enough room for 2 NC400 and 1 SMPS1200, why not build a stereo?

[Freo-1]

Looks like there may be a (subjective) “real improvement” to the basic Hypex amp after all:
 
 
http://www.avrev.com/home-theater-power-amplifiers/stereo-amplifiers/rogue-audio-hydra-hybrid-power-amplifier-review.html