[barrows]

But is this really something that needs sorting out? Bigger problems out there in the audio world than something only audible 1" from the tweeter.

No, there is nothing which needs sorting out, as I have mentioned, what I am hearing is just the normal noise floor of the amps: very smooth, extremely low level hiss, most likely just the thermal noise of the input stage.  And, this noise is only audible at night, on a calm quiet night, ear directly up to the tweeter.  Take into account my home is in a rural area, on 3 acres, with virtually no neighbors, at 9,300'.  There is also only one road, with no traffic at night, within a mile of my house.  It is much quieter here than anywhere with neighbors, or roads with cars, or other people around talking, or anywhere in a suburban or urban environment.
After much thought, I am going to do this build the Hypex way: no AC ground connection (I float my other components as well in respect to AC ground) with secure, and double insulated internal high voltage AC wiring, pin 1(s) direct to chassis through a very short 20 awg wire, nCore input cable shield direct to chassis at a different point than pin 1, but very close to the XLR jack.  I will also remove anodizing/paint from the chassis sections until there is relatively low resistance continuity between the chassis panels, this may provide a little bit of shielding from the outside world, but not really.  Considering the ~1 uF of C directly at the input of the SMPS600s (two of them) I will also place a .01uF cap at the IEC for a little bit of added high frequency filtering.  If this build results in any "problems", then I may re-visit other possible solutions.  I am also considering transformer coupling for the output of my DAC, as this may solve a couple of (very small) problems, and then connecting only the "ground" (actually the shield) of the transformer to pin 1 of the DAC output.  When the build is done, I will post a couple of pics in the approriate thread.

[cab]

from diyaudio.com ncore thread:

     #5637
Julf is online now Julf  Europe
diyAudio Member
 
Join Date: Oct 2011
Location: Amsterdam, The Netherlands
   

"Mine are dead quiet too as they should be."


"Indeed - with a specified 124 dB SNR, pretty much any noise is an indication of some sort of abnormal issue."

[audio-heaven]

If it helps any I also hear nothing but total silence from all of my speakers with the Ncore, even with my ear up against the tweeter, well not until I press play that is 

[barrows]

from diyaudio.com ncore thread:

     #5637
Julf is online now Julf  Europe
diyAudio Member
 
Join Date: Oct 2011
Location: Amsterdam, The Netherlands
   

"Mine are dead quiet too as they should be."


"Indeed - with a specified 124 dB SNR, pretty much any noise is an indication of some sort of abnormal issue."

Nope, totally wrong.  Amsterdam, not exactly a quiet rural area either…  Hahaha.  I will not be addressing this issue anymore, as apparently some folks just do not get it.  The nCore specs have all the answers one would need in the noise output voltage specification.

[Russell Dawkins]

Take into account my home is in a rural area, on 3 acres, with virtually no neighbors, at 9,300'.  There is also only one road, with no traffic at night, within a mile of my house.  It is much quieter here than anywhere with neighbors, or roads with cars, or other people around talking, or anywhere in a suburban or urban environment.

I envy you your acoustic environment! I used to live on 300 acres about 12 miles from the nearest highway in a very quiet loft paneled in acoustic board (we call it Donacona board). When I pressed play on Chesky CDs, I was immediately taken to a not-quite-perfectly-isolated recording studio in New York city. The traffic roar was easily perceptible even though perhaps 60-70dB down. It's amazing what you can hear when it's really quiet!

[Julf]

Nope, totally wrong.  Amsterdam, not exactly a quiet rural area either…  Hahaha.

You'd be amazed. We live on the outermost of the inner city canals, far enough from the tourist ghettos of Central Station and Leidseplein, but also far enough of the high-rises and offices further out. Occasional noise from tourist tour boats and bicycle bells on the front side, but on the back side, surrounded by old buildings with thick brick walls, it is really, really quiet. OK, in the spring the blackbird is annoyingly loud...

I will not be addressing this issue anymore, as apparently some folks just do not get it.  The nCore specs have all the answers one would need in the noise output voltage specification.

Or the SNR specification... That happens to match the voltage spec. Output noise voltage is specified as 25 uV max, maximum output voltage swing is 40 V. 20 log (0.000025/40) is -124.1 dB.

[doug s.]

Nope, totally wrong.  Amsterdam, not exactly a quiet rural area either…  Hahaha.  I will not be addressing this issue anymore, as apparently some folks just do not get it.  The nCore specs have all the answers one would need in the noise output voltage specification.

i, for one, would love to hear if you are able to reduce the noise floor w/any different grounding scheme.  yust ignore the parrots.   

doug s.

[Julf]

yust ignore the parrots.   

Ah, yes, I did forget to note one of the largest contributions to the noise pollution here - the parrot colony in the park. But they are only an issue when they do their dawn and dusk patrols...

[barrows]

julf: Glad to hear that you have a quiet spot.  I am so used to living where I am at, that I would find it hard to move to a more populated area-I am spoiled!  But, unfortunately, I am not sure that I can live here forever, the winter at this elevation can be somewhat tiresome, and in my more advanced years, I anticipate having to move.
I assume the 25 uV of noise would be with shorted inputs, I have some shorting plugs here, so when this current build is done, I will short the inputs and see what I hear.  But, if I remember correctly, the noise voltage of my Pass is specced at about 40-50 uV, and its noise floor, listened for at the tweeter, does seem to be about double (or +6dB  ) that of what I hear from the nCore, so it all makes sense to me...
My reason for exploring other wiring schemes was never in an effort to further reduce the quiescent noise floor, it was an attempt to avoid coupling RF into the system as a whole.  One other thing I am eventually going to try is to add some RF damping (not shielding) to the inside of the top cover of the chassis.  I am much more a believer of damping, as opposed to shielding as actually being successful at shielding RF seems a thankless task, unless has the funds to go to a fully CNCed from billet aluminum style chassis (or maybe molded carbon fiber/STEALTH), and even then the wiring seems like an awfully good path for RF ingress/egress.

[Julf]

Barrows: I can definitely relate to the "advancing years" issue - it is something we do discuss. Living in a historic, listed building sounds romantic, until you have to deal with maintenance and endless narrow, steep and twisting stairs

As to RF damping / shielding, I am not sure it is an issue worth worrying about too much - just look at the amount of high-end gear that places digital high-speed circuits (and often wireless interfaces) inside the same enclosure as audio circuits.

[barrows]

Yeah, totally agreed about not worryinbg too much about RF, but it is something I like to play around with.  Crystal, carbon and such compounds...  I admit that their affects are subtle (if at all).

While I have your ear, I need a tech confirmation.  I see the spec showing CM impedence of the nC400 at 1.5Mohm, I assume this means 750Kohm per phase to G?  Do I have this right?  I need to determine capacitor value for AC coupling a (balanced) DAC's output.  If I have it right, I can use very small caps, which would be nice...

[Julf]

I see the spec showing CM impedence of the nC400 at 1.5Mohm, I assume this means 750Kohm per phase to G?

I assume it is actually 1.5 Mohm from one input (either inverting or non-inverting) to ground. But that doesn't really matter, because you don't reference the signal to ground at all.

I need to determine capacitor value for AC coupling a (balanced) DAC's output.  If I have it right, I can use very small caps, which would be nice...

Unfortunately the impedance that is relevant to the coupling capacitors is the differential mode impedance (104 Kohm), as that is the input impedance that your DAC output feeds.

[barrows]

Oh well, 104K is still pretty decent.  I can get away with a 1uF cap then with no worries...
Thanks...

[milezone]

Just wanted to follow up from a prior post regarding issues I having with my NCores. I'd been away for a couple weeks and wasn't able to get around repairs until recently. An employee at Hypex suggested a possible issue with my speaker posts not being isolated properly. I believe this is where the issue lied. Another problem may have been bad contact due to the binding posts being annealed. Lastly I purchased one of these http://www.apc.com/resource/include/techspec_index.cfm?base_sku=le1200 suggested by Bavmiike (at diyaudio). In one fell swoop made all changes and hooked them up and they work perfectly. Furthermore I believe the apc voltage regulator has improved them to worthwhile degree. I sexond Bavmiike's observations and recommend it for digital components with SMPSs. Thank you for the suggestions and thought and also thanks to the people of Hypex in their ability to isolate the issue from fairly junky iphone pictures, and also for conceiving these ridonkulously good amplifiers.

[mikeeastman]

One of my mono block Ncore has started to something odd when I turn it off, it goes off but after a second it goes back on and off real fast 3 or 4 times stays off for a couple of seconds then goes on and off once more real fast and stays off. Anyone have any idea what going on? 


   Mike

[jtwrace]

One of my mono block Ncore has started to something odd when I turn it off, it goes off but after a second it goes back on and off real fast 3 or 4 times stays off for a couple of seconds then goes on and off once more real fast and stays off. Anyone have any idea what going on? 


   Mike

Are the LEDs on the whole time or do they go off & on too? Have you contacted Hypex?

[mikeeastman]

The Leds go on and off and I can hear the relays clicking on and off also. I send an E-mail to Hypex

[James Romeyn]

I played a classical CD with little bass energy at moderate level.  Then I switched to Knotting Hill soundtrack, heavily equalized and compressed, with loud synth-augmented bass line.  Knotting Hill was several dB louder, especially in the bass, with high energy two octaves lower than the prior CD. 

Major overload of Ncores and/or main speakers or both (main are Dynaudio Esotec 170mm mid bass and Estotec D260 dome, two each per channel, active high-pass 2nd order @ 80 Hz).  The sub amp clips 5 dB below the main system, so I'm sure it clipped badly too.       

Woah!  The resulting cacophony was a physical and emotional shock!  Like the worst LP scratches you ever heard but worse, with awful transient crackle.  Best comparison is aluminum foil crinkled at excruciating level.  I was wondering how many costly drivers blew, but thank God after several seconds all seemed fine.

Kudos to Bruno's protection circuits!  Kudos to Dynaudio power handling!  But still, don't make that mistake with Ncore!

Remote control bass level (below 70 Hz) contributed to my error.  If music program has little energy below 70 Hz there is no aural indication when the bass level is advanced.  I sure knew when I changed the CD! 

[jtwrace]

The Leds go on and off and I can hear the relays clicking on and off also. I send an E-mail to Hypex

Sounds like a power supply issue.  I'd not use it and just wait for Hypex to respond.

[mikeeastman]

Does anyone know how quickly Hypex respond to e-mails, I sent them e-mail 2 days ago about power supply problem and haven't heard back.