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VTV Hypex Ncore NC252MP (It's all Amir's fault)

marcom22

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I just got an NC252MP from AudioPhonics, it's perfect. No ticks or pops when turning on and off, only pure silent operation. There is only a tick when operating system boot-up and load USB driver to communicate with my Topping Dx7s, but afterall no more. Now that I known, I power-on the AMP after Windows loads the desktop.


@amirm What a wonderful AMP, thanks again.
 

VTV Amplifier

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No modification is necessary. Take a look at the build photo here https://vtvamplifier.com/product/vtv-stereo-amplifier-based-on-hypex-ncore-nc252mp/ Pin#1 is tied directly to chassis at the XLR and is AES48-19 compliant. Hypex acknowledges that NC252MP can make a transient on turn-off and has resolved this issue. Hypex says that it occurs on very few systems so they do not consider it a defect and I can confirm this from the many of these we sell.
 

Matias

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Nice, it is always good to show the internals on the official website. :)

IMG_8246-scaled.jpg
 

Feanor

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In case of my VTV NC252MP received a few weeks ago, it does NOT look exactly like the picture now on the website There it looks like Pin 1 is connect to the chassis close to the connector; it's hard to make out how module's input cable shield is connected ...
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1599139248996.png


My VTV NC252MP has the XLR Pin 1 is connected to the XLR shell and thence to chassis Ground at the IEC ground connection point. The only thing that might be a issue is that the amp module's input cable shielding is also connect a Pin 1, (and thence to Gnd), rather being directly connected to chassis Gnd with its own connection. The latter would be in accord with guru advice.

In practical terms the amp is almost completely silent at power up & down. There is no "thump" or other loud noise on either occasion. On shut down there is a really tiny "tsit" from the speakers you can hear from about three feet away. I'm certainly not going to bother trying to fix the wiring on this account.
 
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CDMC

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No modification is necessary. Take a look at the build photo here https://vtvamplifier.com/product/vtv-stereo-amplifier-based-on-hypex-ncore-nc252mp/ Pin#1 is tied directly to chassis at the XLR and is AES48-19 compliant. Hypex acknowledges that NC252MP can make a transient on turn-off and has resolved this issue. Hypex says that it occurs on very few systems so they do not consider it a defect and I can confirm this from the many of these we sell.

It is nice to see that the wiring has been been corrected in the new amps being shipped. There is still one issue, the case is anodized (anodizing acts as an insulator) and the screws that ground to the case are not threaded into the case, they are smaller than the holes and pass through to the nuts on the other side. As such, the wires are not grounded to the case, unless the anodizing has worn away. A quick hit with a Dremel with a sanding wheel where the wires ground to the case will correct this.
 

Rick Sykora

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CDMC

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I do hit the chassis with a dremel around the inside of the XLR mounts to remove the anodizing so solder lugs mounted behind the XLR make solid connection to chassis.

Thanks for clarifying that.
 

Rick Sykora

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I just got an NC502MP which should be the latest version. No ticks or pops when turning on and off, only pure silent operation.

Which brand is your Hypex or is it DIY? Am trying to narrow down the power down transient conditions and am stepping up to NC502MP. Thanks!
 

Matias

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Rick Sykora

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Matias

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Rick Sykora

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Glad it worked out for you!

Hypex support indicates the transient is more likely in unbalanced sources. They have an improvement forthcoming, but not yet in production.

In my case, the transient also follows the speaker sensitivity. It rarely happens on the Selah Integrity for example. Your Thiels are fairly sensitive though, so is not a sole indicator, but likely explains why there is mixed reports on occurrence. Hypex is still my best option, but just going to have to be patient I guess. :)
 
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Matias

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Glad it worked out for you!

Hypex support indicates the transient is more likely in unbalanced sources. They have an improvement forthcoming, but not yet in production.

In my case, the transient also follows the speaker sensitivity. It rarely happens on the Selah Integrity for example. Your Thiels are fairly sensitive though, so is not a sole indicator, but likely explain why there is mixed reports on occurrence. Hypex is still my best option, but just going to have to be patience I guess. :)
I normally use the NC502MP with Monitor Audio PL100 speakers, as per my signature.
 
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CDMC

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Matias

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Do I see fancy power cords and cables back there? Have you been cheating on us?
Oh you have seen nothing yet. :)
But in this case it is a Chinese 15usd power cable from Aliexpress.
 

cranks

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Hi there,

Been a long time lurker as I have been researching class-d amps and this site has helped me a lot! Thanks to all who have contributed!

In my research I have found a local supplier of class-d amps who uses high quality transformers instead of smps.

What are the pro's and con's of his approach??

BTW...I am not a technical person, just an average Joe who wants to upgrade my amps and be armed with the right knowledge to do so!
 
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Matias

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Hi there,

Been a long time lurker as I have been researching class-d amps and this site has helped me a lot! Thanks to all who have contributed!

In my research I have found a local supplier of class-d amps who uses high quality transformers instead of smps.

What are the pro's and con's of his approach??

BTW...I am not a technical person, just an average Joe who wants to upgrade my amps and be armed will the right knowledge to do so!
IMO big transformer adds weight, cost, possibly hum, and switchers don't while also supplying all the current needed and better stabilization for peaks.
 
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