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Old 20th September 2012, 11:39 PM   #5081
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Default while we are discussing Ncore measurements...

has anyone run a PowerCube test on them (and / or on any of the TI/ Nat Semi LM chipamp modules)? If so may we see the data?


AudioGraph - home of the LoadBox and the PowerCube

http://www.audiograph.se/Downloads/P...e_complete.pdf

http://theaudiocritic.com/back_issue...ritic_20_r.pdf
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Old 21st September 2012, 06:40 PM   #5082
tony399 is offline tony399  United Kingdom
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Quote:
Originally Posted by jlaakso View Post
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
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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Old 21st September 2012, 06:46 PM   #5083
jlaakso is offline jlaakso  Finland
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Quote:
Originally Posted by tony399 View Post
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!
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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Old 21st September 2012, 07:17 PM   #5084
tony399 is offline tony399  United Kingdom
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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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Old 22nd September 2012, 12:34 PM   #5085
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Is it possible to build a pair of NCORE's in a 1U housing. It would mean very limited space on both sides I guess...
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Old 22nd September 2012, 01:36 PM   #5086
pos is offline pos  Europe
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The SMPS600 would not fit, even with the spacers removed
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Old 22nd September 2012, 01:51 PM   #5087
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Hmmm, suspected that. Too bad :-(
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Old 24th September 2012, 06:38 AM   #5088
Zoran is offline Zoran  Serbia
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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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Last edited by Zoran; 24th September 2012 at 06:47 AM.
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Old 24th September 2012, 08:44 AM   #5089
Julf is offline Julf  Europe
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Quote:
Originally Posted by Zoran View Post
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?
It was covered in this post by Bruno:

Quote:
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.
No information about what the maximum allowable gain.is, but the app note makes it clear that "less is better".
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Old 1st October 2012, 10:01 PM   #5090
frankl is offline frankl  Germany
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Default 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?
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