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NCORE MP Build using Ghentaudio Kit.

MenloBob

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I have no experience with these particular modules, and it is clearly meant to be installed as you have done, but I wonder why it isn't rotated 180 in the case, so that the power leads would be very short, rather than very long. The audio I/O runs would still be about the same, mid-board to the rear.

You want to keep the signal lines as short as possible and far away from the ac. Power lead length doesn’t really matter.
 

Red_Baron

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My NC502MP build has been great so far. I got tired of waiting for my Ghent RCA --> XLR cables with the slow standard shipping. Amazon fixed that in 2 days.

After adding the amplifier, my room calibration preference for the front speakers changed. Previously, I thought that Audyssey with LFE+main sub crossed at 80 Hz sounded best. With the Hypex amplifier, the older setting is boomy and sloppy qualitatively. Now I set it to bypass L/R (no corrections for the mains) and LFE+main crossed at 40 Hz for the subwoofer. My suspicion is that the Marantz AVR couldn't drive the bass peaks well enough. These towers are 4 Ohms for much of the bass region.

The orientation of the Ghent NC502MP kit came up earlier. A crude picture edit shows why the Ghent kit was done properly because the power supply section is farthest away from the XLR and speaker connections. Swapping front and rear panels and then mirroring the rear panel would be needed to shorten the AC power connection to the Hypex board while keeping the XLR input and speaker out wires short and clean.

Ghent_NC502MP_reverse.png
 
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bcurtin

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My case from Ghent arrived (right on time!) and I put together my NC252MP-based amplifier today.

Didn't take long at all and Archimago's guide on his blog was a good resource. The build took < 2 hrs and went smoothly, except for a couple minor issues: (1) one XLR connector was missing a screw/washer/nut assembly and (2) the input signal wire gauge seemed a little too high for the solder-less XLR connectors - I really had to tighten the compression bolt before getting the wires secure, but solder probably would have made a better connection. I emailed Ghent about the XLR connector screw but might find something else in the meantime.

I'm currently using a D30 + Rotel RA-1572 and used the Rotel pre-amp outputs to the NC252. I haven't done a proper AB test but the NC252 sounds great - solid bass, clear highs, and it stayed clean and detailed at high power. I've had an annoying buzz/hum from the Rotel that's noticeable close to the tweeter and still there with the NC252, so I'll try the D30 as a pre-amp next and see if the Rotel is to blame.

@Red_Baron I noticed the same transient/pop during power down but not power up. My tweeters are old and costly to replace so hopefully this isn't an issue, but let me know if you figure anything out. I'm considering just letting the amp idle rather than shutting it off.
 

Red_Baron

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@Red_Baron I noticed the same transient/pop during power down but not power up. My tweeters are old and costly to replace so hopefully this isn't an issue, but let me know if you figure anything out. I'm considering just letting the amp idle rather than shutting it off.

Hypex provides a mute option that might help by asserting this at startup and just before/at shutdown. Manually asserting Amplifier mute using the +5V standby supply and a jumper cable would test the theory. A 555 timer should be enough to automate the delayed turn on and off mute if the amplifier mute function idea is viable.

Screen Shot 2020-02-02 at 1.09.45 PM.png

Screen Shot 2020-02-02 at 1.10.37 PM.png



Adding an additional amplifier on / standy switch to the chasis that keeps the AC mains on but puts the amplifier into standby with only the 5V standby rail on would work. The switch would simply connect "PS Enable" to "VOUT,STANDBY" or "GND" for on/off states.

Asserting the amplifier mute function with the 5V standby supply (with 250mW idle power) tied to this standby enable switch would automate on/off muting behavior with some additional simple logic circuitry. On 24/7, the standby +5V supply is about 0.2kWh per month.


Screen Shot 2020-02-02 at 1.10.57 PM.png


---------------

I also though about adding a 12V trigger. Adding this should be simple.
Some background on 12V trigger circuits is available from Elliot Sound Products.

Amazon has some cheap modules that might be suitable.
A second Amazon option.

A master slave power strip is even simpler though.
 

bcurtin

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Hypex provides a mute option that might help by asserting this at startup and just before/at shutdown. Manually asserting Amplifier mute using the +5V standby supply and a jumper cable would test the theory. A 555 timer should be enough to automate the delayed turn on and off mute if the amplifier mute function idea is viable.

View attachment 48432
View attachment 48433


Adding an additional amplifier on / standy switch to the chasis that keeps the AC mains on but puts the amplifier into standby with only the 5V standby rail on would work. The switch would simply connect "PS Enable" to "VOUT,STANDBY" or "GND" for on/off states.

Asserting the amplifier mute function with the 5V standby supply (with 250mW idle power) tied to this standby enable switch would automate on/off muting behavior with some additional simple logic circuitry. On 24/7, the standby +5V supply is about 0.2kWh per month.


View attachment 48434

---------------

I also though about adding a 12V trigger. Adding this should be simple.
Some background on 12V trigger circuits is available from Elliot Sound Products.

Amazon has some cheap modules that might be suitable.
A second Amazon option.

A master slave power strip is even simpler though.

Thanks for sharing - I had previously looked into adding a 12 V trigger to the amp and was aware of these pins in the data sheet, but didn't consider using this to prevent power up/down transients.

I've been using the Rotel RA-1572 and NC252 as a pre/power amp (RCA -> XLR) the past few days and found that transients are particularly noticeable when the Rotel isn't powered on or an input relay hasn't been enabled. Powering the NC252 down before the preamp output relays are disabled seems to eliminate the issue, so I may be able to work around the issue with power sequencing but we'll see.
 

mslim

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The thermal paste really helps to transfer the heat from the amp module to the case - under sustained load it will get fairly warm, very quickly - which is good, since that means the heatpaste is effective in transferring the heat to the case.
Between the circuit board and the amp metal backplate of the module there are thermalpads pre-applied by Hypex in several places. For those who want to really make 100% sure to ensure the best-possible heat transfer, it might be worthwhile to temporarily remove the backplate, and replace the applied thermalpads with higher quality thermalpads such as the ones from Arctic.

On this amp I've used Arctic MX-4 thermal paste, which I usually use on 'Monster' Noctua Ryzen Threadripper coolers, but any non-conductive thermal paste should do just fine.

Won’t this make everything messy?
 

Red_Baron

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Removing pops/clicks at power on/off

I ran some tests today to verify the theory that asserting Mute (J4.13 or J4.4) on power up and power off will solve the problem.

It does work to completely remove the power on/off pops and clicks.

This requires keeping the +5V standby power always on for control to make this will work. With this method, the AC mains will remain on and the +5V standby supply will be used to manage the main power on and off behavior. I suspect that some commercial builds use this method with front panel switches. A prior post of mine estimated the quite small cost of leaving this on 24/7.

The next step is to build a prototype with an external +12V trigger input and an optical isolator and a Schmitt trigger inverter IC. Timing information from Hypex data sheets indicate that simple logic with no delays will be fine since Mute is faster acting than turn on/off.



IMG-0838.JPG
 

Red_Baron

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Some parts arrived and I got around to building a breadboard 12V tirgger circuit along with the mute circuit idea that I suggested earlier. I used a 555 timer in a Schmitt Trigger logic inverter mode to make PS_enable be NOT mute.

My assement is as follows
  1. an optically isolated external 12V trigger circuit is simple to do using the +5V standby supply
    1. everything is as expected here
    2. to keep things entirely isolated from the +12V trigger source, make sure to get a 3.5mm socket that is isolated from the chasis
      1. this avoids a potential ground loop
      2. of course the analog input side ground sharing cannot be avoided.
  2. J4.13 Amplifier Mute is a mixed bag
    1. with mute at a logic '1' of +5V, there are no click/pop sounds at power on or off
    2. but, when mute is released to use the amplifier, the click and pop sounds come back.
      1. this makes this option not viable
      2. to confirm the behavior, I put a momentary switch on the breadboard to control J4.14 Mute
        1. it made no difference from the 12V trigger circuit I tried first
        2. and RC filter on the output made no difference
    3. fixing the click/pop would mean doing something invasive to the core amplifier circuit or applying some sort of DC correction to the inputs
  3. The trigger is very convenient. It will be worth the effort to drill the back panel.
    1. an extra switch (dpdt) makes it simple to have 3 useful states
      1. Off with the AC mains switch as a global On/Off in the off state
      2. with AC mains ON, J6.9 PS Enable would then be switched by the DPDT switch from
        1. external trigger selectable wakeup
          1. +5V standby supply would be always on here at 250mW 24/7.
        2. +5V J6.3 standby supply would switch to J6.9 PS enable just like the Ghent cable does be default
    2. this avoids having to create a logic OR function with an active circuit
 

Red_Baron

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Update on my 12V trigger.

My semi-permanent circuit is done. After a week of use, everything works well. Getting the circuit small enough to fit on the Hypex J6 header was much more effort than I anticipated. A small custom PCB is the way to go for this.

Given the time and effort to put this feature in, it was frankly not worth the time to make a DIY version.

For those who want to add this feature, which is wonderful now that I have it, simple commercial solutions that others posted are the way I would go if I could start over from the beginning. There is no meaningful cost savings or feature benefit for the DIY version.
Audiophonics solution for a single unit
Power strip with 12V relay switched outlets for multiple amplifiers
 

JimB

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Update on my 12V trigger.

My semi-permanent circuit is done. After a week of use, everything works well. Getting the circuit small enough to fit on the Hypex J6 header was much more effort than I anticipated. A small custom PCB is the way to go for this.

Given the time and effort to put this feature in, it was frankly not worth the time to make a DIY version. ...
But, I am intrigued with how you did it! Willing to share details? I was the king of circuits in cable head-shells at work. ;)
 

Red_Baron

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But, I am intrigued with how you did it! Willing to share details? I was the king of circuits in cable head-shells at work. ;)

The circuit is simple. Originally I planned to use the 555 Timer input to control the J4.14 Mute signal. This did not help with click and pops, so it was omitted for simplicity. A 4n35 optical isolater takes the external +12V trigger. Pin 6 of the 4N35 gives access to the NPN base, creating an "OR" function with for the panel "On Swicth". The 555 Timer works and an inverter with hysteresis.
NC502MP_Ext_Triger_Ckt.png


The wiring is not as clean as I would like. However, only static DC signals are routed. From the panel the two 2-wire cables to/from the 3.5mm trigger in and panel "On" switch route below the input and around the corner on the bottom of the case. I spliced some electronics kit wires and headers to make the connections. I did not want to cut up the Ghent J6 cable.

Some pictures.
IMG_0846.jpeg IMG_0847.jpeg IMG_0848.jpeg IMG_0849.jpeg
 

sfabio

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fixing the click/pop would mean doing something invasive to the core amplifier circuit or applying some sort of DC correction to the inputs
So even with your trigger circuit clicks and pops remain the same? :(
 

Koeitje

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Where can I buy these modules in Europe? The NC400 is too expensive for me for a first time build. But all of these modules are OEM only :(.
 

Red_Baron

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So even with your trigger circuit clicks and pops remain the same? :(

The trigger is independent of the power on/off click/pop.
By default, the Ghent kit directly ties +5V standby supply to PS.enable. All the trigger does is put a switch from +5V standby to PS.enable with simple logic.
 

sfabio

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The trigger is independent of the power on/off click/pop.
By default, the Ghent kit directly ties +5V standby supply to PS.enable. All the trigger does is put a switch from +5V standby to PS.enable with simple logic.
Yes, I don't need a trigger, I'm searching a way to avoid pops and clicks so, if You have tried a logic that sequences mute-power on-mute-power off without success, the only way I know is to add a speaker protection circuit that disconnects speakers before power off and reconnects it after power on. The only thing that makes me puzzled is the declaration of Rouge audio and Kjfaudio of pop free power on and off with the control logic.
 
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Koeitje

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Where can I buy these modules in Europe? The NC400 is too expensive for me for a first time build. But all of these modules are OEM only :(.
Anyone that can tell me how you are all getting these nice modules, I'm looking for an NC502MP because that seems to be the easiest build and not that expensive..
 

dkinric

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I got my Hypex off ebay several months ago, and the case and wiring harness from Ghent Audio. Someone had about a dozen modules and was selling them greymarket - not really authorized, but new and legit. You can try a Hypex search on ebay, although only a few on there now..
 

Matias

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