Hypex Ncore

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tony399

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Joined 2010
jlaakso said:
Wouldn't that imply that PSU of the class D amp is generating noise into your mains network which your sensitive (presumably with high gain) phono preamp picks up?

I am really out my areas of expertise, but how would that be visible in the output of amp if the PSU is generating noise back to mains network? And to make sure, I am not trying to imply anything, I just don't understand :)
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analog_sa, like jlaakso says, could be the psu and not the NC400 itself, are you using smps?
Have you tried a simple mains filter on the amp supply (eg 1uf X1 polyprop across live and neutral)? Could you possibly try a linear supply?
Seems a shame to have such a great amp that you can't use for your vinyl!
 
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jlaakso

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Joined 2010
tony399 said:
analog_sa, like jlaakso says, could be the psu and not the NC400 itself, are you using smps?
Have you tried a simple mains filter on the amp supply (eg 1uf X1 polyprop across live and neutral)? Could you possibly try a linear supply?
Seems a shame to have such a great amp that you can't use for your vinyl!
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I think he said it's not Hypex amp, just class D amp. That's one more reason I originally thought it would best to troubleshoot the amp itself, not someone else's different amp (ncore in this case). But then again, it is good to know ncore's output does not suffer from excess offset :)
 
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tony399

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Joined 2010
I assumed it was NC400 because he asked for the measurement, fair enough. I don't use smps with mine (already had all the parts for some very good linear supplies) and I understand the Hypex smps (and amps) to be superior to many for rfi and emi so same scenario may still apply.
Could be time for him to take the plunge into nCore, I fully recommend it! :)
 
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Julf

Member
Joined 2011
Zoran said:
Hi somebodu hava an information about the gain of an NC400 board
R 141 value to change?
And what is max gain allowed by the designer?
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It was covered in this post by Bruno:

Not much has changed since http://www.hypex.nl/docs/appnotes/gain_appnote.pdf

Gain is 4.17*(1+2*Rf/Rg). Rg=1.2k, Rf=2.2k. Rg, as noted in the bugs section of the data sheet is not marked (will be in the future), but it's called R141 and it's the one furthest to the left of the input connector. The maximum gain reduction you can get is 13.4dB, which is when you remove R141 altogether.
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No information about what the maximum allowable gain.is, but the app note makes it clear that "less is better".
 
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frankl

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Joined 2012
Background noise instead of "dead silent"

Hi, using Hypex documentation and this great thread I have built a stereo (dual mono) setup with two nc400 and two smps600.

Unfortunately, when no music is played, the amps are not "dead silent" as several people reported here. I have a background noise over a wide frequency range which is still audible at the listening position (about 2.5m from the speakers). I can even hear it when not so loud music is played.

Except for this problem the amps seem to work as described here and in other places (that is, wow!).

I have changed and checked a few things but nothing had an effect on the background noise. I would appreciate any help to identify (and hopefully resolve) this problem.

My setup is as follows: I build the amps into my (closed) rack with a wood bottom and front, and try to avoid non-needed connections.

The SMPS600 are about 10cm away from the nc400. Mains supply comes from an Isotek power conditioner via a shielded cable, the brown and blue input cables of the smps600's are well twisted and away from all other cables. The harness from smps600 to nc400 is also well twisted. Since they were long enough I have soldered XLR plugs directly to the input cable provided by Hypex. They go into the balanced XLR output of an Ayre QB-9 DAC (pins 3,4 of the NC400 input, shield and nAMPON wire, connected to pin1 of the XLR).

Speakers have fullrange drivers (Fostex FE206, rated 96dB) and are connected via solid core CAT6 cable (colored=+, whites=-) with just enough insulation removed to fit the ends into the screws on the NC400 (from the same side).

I have tried a different type of mains cable, other speaker cables, put a sheet of copper between DAC and amp, tried mains power directly from a wall socket without filter; but nothing influenced the background noise. The noise is still there if I switch off the DAC. The noise goes away when I mute the nc400 by disconnecting the nAMPON wire.

Compared to my previous setup I have only changed the amp (a modified version of a TrendsAudio TA-10.1), the background noise was much lower and not audible at the listening position.

What am I doing wrong?
 
bavmike

bavmike

Banned
Joined 2011
Hello guys. I built myself a dual mono ncore with the SMPS 600's. The amps work perfectly at home, but I brought them to my shop to setup a sound room and they don't seem to like the electricity in there. The shop has 600v coming in and then it's split into 230 3 phase and 120 single phase through a big transformer. I think the transformer is making dirty power because all of the red lights on the amps come on but no sound. I think the internal microprocessor is detecting dirty power and putting them into standby. I tried hooking them up through my monster power HTS 1000 power conditioning bar. It must of helped a bit because one channel started working and the other worked intermittently. I'm guessing the protection circuitry in the one amp is slightly more sensitive then the other. Does anybody know what I can do for a reasonable price to clean up this power? I read somewhere that people are combining step up transformers with step down transformers to clean up power. Not sure if that would be effective.
 
bavmike

bavmike

Banned
Joined 2011
bavmike said:
Hello guys. I built myself a dual mono ncore with the SMPS 600's. The amps work perfectly at home, but I brought them to my shop to setup a sound room and they don't seem to like the electricity in there. The shop has 600v coming in and then it's split into 208 3 phase and 120 single phase through a big transformer. I think the transformer is making dirty power because all of the red lights on the amps come on but no sound. I think the internal microprocessor is detecting dirty power and putting them into standby. I tried hooking them up through my monster power HTS 1000 power conditioning bar. It must of helped a bit because one channel started working and the other worked intermittently. I'm guessing the protection circuitry in the one amp is slightly more sensitive then the other. Does anybody know what I can do for a reasonable price to clean up this power? I read somewhere that people are combining step up transformers with step down transformers to clean up power. Not sure if that would be effective.
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Here's a picture of my transformer for anyone who knows more about them. Thanks in advance
 

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analog_sa

analog_sa

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Joined 2002
jlaakso said:
I think he said it's not Hypex amp, just class D amp. That's one more reason I originally thought it would best to troubleshoot the amp itself, not someone else's different amp (ncore in this case). But then again, it is good to know ncore's output does not suffer from excess offset :)
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Not sure how this confusion came about. As i very clearly stated, these were impressions of an entirely different class D amp. It totally messed up the sound of my phono setup, probably because of serious RF leak into the speaker cables. There is nothing to troubleshoot - class D amps work like that even with a linear supply. In comparison the Hypex has significantly less RF output (600mV as opposed to 1300mV). Whether this is good enough i simply don't know but for me it is a concern.

I would certainly be curious to know if anyone is using a Hypex in a high gain phono system and they are happy with the sound.
 
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Julf

Member
Joined 2011
bavmike said:
The shop has 600v coming in and then it's split into 230 3 phase and 120 single phase through a big transformer. I think the transformer is making dirty power because all of the red lights on the amps come on but no sound.
Click to expand...

It might not be dirty - just out of range. I think the first thing to do is to simply measure the voltage on the 120 V circuit with the AC voltage range of a multimeter.
 
bavmike

bavmike

Banned
Joined 2011
Julf said:
It might not be dirty - just out of range. I think the first thing to do is to simply measure the voltage on the 120 V circuit with the AC voltage range of a multimeter.
Click to expand...

I didn't use a meter to test but my monster power bar said 120v on the digital readout. How sensitive are the units to power overages? The SMPS 600 says 132v max in the data sheet, but looking back on previous posts some people have had problems with the voltage protection not being adjusted for much leniency. My units are from the second batch in January before this problem was discovered. I'm wondering now if I can make the adjustment from home, send them back to the factory for adjustment, or just buy a voltage regulator and set it at 110v?
 
J

Julf

Member
Joined 2011
bavmike said:
I didn't use a meter to test but my monster power bar said 120v on the digital readout.
Click to expand...

OK, that is probably pretty accurate. Then the "dirtiness" enters - there could be significant peaks on that 120 V. I wonder if the auto-voltage circuit gets confused?

I'm wondering now if I can make the adjustment from home, send them back to the factory for adjustment, or just buy a voltage regulator and set it at 110v?
Click to expand...

Any chance of borrowing an adjustable transformer?
 
bavmike

bavmike

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Joined 2011
troystg

troystg

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Joined 2004
Your Monster power bar is a conditioner or does it regulate also? 120 is VERY high for a home circuit, usually 110-115VAC is the norm.

Get (borrow) a Fluke 87 series meter and use the record the max/min voltage function to see if it varies up any..
I had the same issue with a linear power supply on my UcD amps.. My line voltage was 118VAC so I put a cl60 in series and upped the resistors values in my twisted pair power supply PCBs and was able to just squeek under the limit.

I don't know if the Hypex SMPS has an auto adjust funtion to switch between 115 and 230 VAC.
 
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